Enzymes and Digestion Quiz
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Questions and Answers

What occurs to an enzyme when exposed to extreme pH levels?

  • Heightened activity at maximal velocity
  • Increased affinity for substrates
  • Optimized reaction rates
  • Denaturation and loss of function (correct)

    • Which statement accurately describes maximal velocity (Vmax)?

  • It is the highest reaction rate possible with saturated enzyme active sites (correct)
  • It occurs at a low substrate concentration
  • It is the rate at which the enzyme is entirely unsaturated
  • It is directly influenced by temperature changes

    • What is indicated by a low Km value for an enzyme?

  • Poor enzyme efficiency in catalyzing reactions
  • Enzyme activity decreases at lower temperatures
  • Low substrate concentration can effectively saturate the enzyme (correct)
  • High substrate concentration is needed to achieve ½ Vmax

    • In what way does substrate concentration affect enzyme activity?

    <p>Substrate concentrations have no effect once exceeding Vmax</p> Signup and view all the answers

    What is the primary impact of aging on pepsin enzyme function?

    <p>Improper functioning due to altered stomach acidity</p> Signup and view all the answers

    At what pH does salivary amylase exhibit optimal activity?

    <p>6-8</p> Signup and view all the answers

    What is the consequence when all active sites of an enzyme are occupied?

    <p>Maximal velocity (Vmax) is achieved</p> Signup and view all the answers

    How do extremes of temperature generally affect enzyme activity?

    <p>They can lead to denaturation and loss of function</p> Signup and view all the answers

    What does the plateau in reaction rate signify at high substrate concentrations?

    <p>Enzyme active sites are saturated</p> Signup and view all the answers

    What effect does a decrease in temperature generally have on enzyme activity?

    <p>It reduces molecular movements, thereby lowering reaction rates.</p> Signup and view all the answers

    How does pH affect enzyme activity?

    <p>Changes in pH can lead to irreversible denaturation of the enzyme.</p> Signup and view all the answers

    What is the primary effect of increasing substrate concentration on enzyme activity, up to a certain point?

    <p>It saturates the enzyme, leading to a maximum rate of reaction (Vmax).</p> Signup and view all the answers

    What is the primary consequence of enzyme denaturation?

    <p>The enzyme’s active site may become distorted.</p> Signup and view all the answers

    How is Vmax defined in enzyme kinetics?

    <p>The highest reaction rate achieved by the enzyme when all active sites are saturated.</p> Signup and view all the answers

    What typically happens to enzyme activity as the temperature approaches the enzyme's optimum temperature?

    <p>Enzyme activity increases due to enhanced molecular movement.</p> Signup and view all the answers

    Which factor is most likely to cause a change in the Vmax of an enzyme reaction?

    <p>A change in enzyme concentration.</p> Signup and view all the answers

    What primarily governs the rate of an enzyme-catalyzed reaction when substrate concentration is much lower than the Km value?

    <p>The concentration of the enzyme.</p> Signup and view all the answers

    What happens to the rate of enzymatic reaction when substrate concentration is much greater than Km?

    <p>The reaction becomes zero order and rate is constant at Vmax.</p> Signup and view all the answers

    How does a decrease in pH impact enzyme activity?

    <p>It may lead to denaturation and reduce enzymatic activity.</p> Signup and view all the answers

    Zymogens are important because they allow enzymes to be activated only when needed. What is a consequence of their activation?

    <p>They undergo irreversible changes during the activation process.</p> Signup and view all the answers

    What is the relationship between enzyme concentration and reaction rate when substrate is unlimited?

    <p>The reaction rate increases linearly until a maximum rate is reached.</p> Signup and view all the answers

    Which of the following accurately describes the concept of Vmax in enzyme kinetics?

    <p>It is the maximum rate of reaction when all enzyme active sites are saturated.</p> Signup and view all the answers

    In terms of enzyme kinetics, how is a first-order reaction characterized?

    <p>The reaction rate is directly proportional to substrate concentration.</p> Signup and view all the answers

    Which factor does NOT affect enzyme denaturation?

    <p>Moderate substrate concentrations.</p> Signup and view all the answers

    What might cause an enzyme's activity to decrease as product accumulates?

    <p>Changes in enzyme conformation due to product binding at allosteric sites.</p> Signup and view all the answers

    What type of bonds are responsible for holding the general shape of proteins together during their folding process?

    <p>Ionic bonds</p> Signup and view all the answers

    Which of the following statements about high energy bonds in ATP is correct?

    <p>They are found between phosphate groups.</p> Signup and view all the answers

    Which compound is considered a high energy compound among the following?

    <p>GTP</p> Signup and view all the answers

    What characterizes ionic bonds as discussed?

    <p>They involve transfer of electrons.</p> Signup and view all the answers

    Which type of bond is weaker than covalent bonds and involves the electrostatic attraction of a hydrogen atom?

    <p>Hydrogen bond</p> Signup and view all the answers

    What is the biomedical importance of ionic bonds in proteins?

    <p>Supporting protein folding</p> Signup and view all the answers

    Which high energy compound is primarily used as an energy currency in metabolism?

    <p>ATP</p> Signup and view all the answers

    Which of the following is NOT a characteristic of non-covalent bonds?

    <p>They are generally stronger than covalent bonds.</p> Signup and view all the answers

    What is the main effect of competitive inhibition on the apparent Km of an enzyme?

    <p>It increases the Km value.</p> Signup and view all the answers

    Which statement correctly describes non-competitive inhibition?

    <p>It binds at a site other than the substrate-binding site.</p> Signup and view all the answers

    What result is observed when a competitive inhibitor is added to an enzyme reaction?

    <p>Vmax remains unchanged and Km increases.</p> Signup and view all the answers

    What characterizes a substance that is classified as an inhibitor in enzymatic reactions?

    <p>It can decrease the velocity of an enzyme-catalyzed reaction.</p> Signup and view all the answers

    Why are statin drugs considered competitive inhibitors in cholesterol biosynthesis?

    <p>They structurally resemble the natural substrate of a crucial enzyme.</p> Signup and view all the answers

    What is the consequence of severe deficiency of glutamine in the body?

    <p>Convulsions</p> Signup and view all the answers

    What is the impact of a non-competitive inhibitor on the enzyme's Vmax?

    <p>It reduces the Vmax without affecting Km.</p> Signup and view all the answers

    In competitive inhibition, what type of complex is formed at the active site of the enzyme?

    <p>Enzyme-inhibitor complex (EI).</p> Signup and view all the answers

    Which of the following amino acids is directly linked to obesity?

    <p>Sulfur-containing amino acids</p> Signup and view all the answers

    What distinguishes non-competitive inhibitors from competitive inhibitors?

    <p>Non-competitive inhibitors do not resemble the substrate.</p> Signup and view all the answers

    What can result from defects in the globin protein of hemoglobin?

    <p>Hemolysis and oxygen delivery issues</p> Signup and view all the answers

    What serious condition can arise from a deficiency of immunoglobulins in the body?

    <p>Increased susceptibility to infections</p> Signup and view all the answers

    What might be a consequence of excessive intake of over-the-counter amino acids, especially in athletes?

    <p>Kidney overload and potential failure</p> Signup and view all the answers

    What is a potential outcome of inborn errors in amino acid metabolism?

    <p>Mental retardation and blindness</p> Signup and view all the answers

    Which of the following is a role of hydroxy-containing amino acids in the body?

    <p>Signal transduction</p> Signup and view all the answers

    What can result from abnormalities in structural proteins such as collagen?

    <p>Skeletal deformities</p> Signup and view all the answers

    What is the primary role of zymogens in the body?

    <p>To prevent auto-digestion and intravascular coagulation.</p> Signup and view all the answers

    Which statement accurately describes the significance of allosteric sites on enzymes?

    <p>They bind effectors which can modify enzyme activity.</p> Signup and view all the answers

    What happens during feedback inhibition in metabolic pathways?

    <p>End products inhibit the activity of earlier enzymes in the pathway.</p> Signup and view all the answers

    Covalent modification of enzymes primarily occurs through which process?

    <p>Addition or removal of phosphate groups to specific residues.</p> Signup and view all the answers

    Enzyme synthesis can be regulated by changes in cellular conditions. Which statement describes this regulation?

    <p>It deals with both induction and repression over longer periods.</p> Signup and view all the answers

    What characterizes the committed-step enzyme in a metabolic pathway?

    <p>It is the first irreversible reaction unique to the pathway.</p> Signup and view all the answers

    Which type of effectors enhance the catalytic activity of allosteric enzymes?

    <p>Positive effectors</p> Signup and view all the answers

    What distinguishes short-term regulation of enzyme activity from long-term regulation?

    <p>Short-term regulation occurs in seconds to minutes instead of hours to days.</p> Signup and view all the answers

    How does increasing substrate concentration impact enzyme activity when approaching Vmax?

    <p>All active sites are occupied, leading to constant velocity.</p> Signup and view all the answers

    What does a high Km value imply about an enzyme's affinity for its substrate?

    <p>The enzyme requires a high substrate concentration to achieve half-maximal velocity.</p> Signup and view all the answers

    Which of the following factors does NOT affect the reaction velocity of an enzyme-catalyzed reaction?

    <p>The molecular weight of the substrate</p> Signup and view all the answers

    What is the primary effect of denaturation on an enzyme regarding substrate interaction?

    <p>Alters the enzyme's active site, preventing substrate binding.</p> Signup and view all the answers

    Under which condition would a reaction appear to be first-order?

    <p>When substrate concentration is constant and low.</p> Signup and view all the answers

    What outcome results when an enzyme is exposed to an environment outside its optimal pH range?

    <p>The enzyme may undergo irreversible denaturation.</p> Signup and view all the answers

    What is the significance of achieving maximal velocity (Vmax) in an enzyme-catalyzed reaction?

    <p>All enzyme active sites are saturated with substrate.</p> Signup and view all the answers

    What does the term 'plateau' refer to in the context of enzyme kinetics?

    <p>The stage of enzyme saturation with substrate.</p> Signup and view all the answers

    What is the significance of the α or β designation in glycosidic bonds?

    <p>It specifies the orientation of the hydroxyl group involved in the bond formation.</p> Signup and view all the answers

    Why can maltose be digested by the body while cellulose cannot, despite both being composed of glucose units?

    <p>The glycosidic bond in maltose is α, while that in cellulose is β.</p> Signup and view all the answers

    What characterizes the formation of peptide bonds?

    <p>They bind amino groups and carboxylic groups of two amino acids.</p> Signup and view all the answers

    What is a prominent feature of ester bonds?

    <p>They involve the condensation of glycerol and carboxylic acids.</p> Signup and view all the answers

    What enzyme is responsible for the breakdown of acetylcholine?

    <p>Esterase</p> Signup and view all the answers

    What is the primary consequence of peptide bond denaturation in proteins?

    <p>It does not affect the primary structure of the protein.</p> Signup and view all the answers

    What is the result of a glycosidic bond formation between two monosaccharides?

    <p>Formation of a disaccharide or polysaccharide.</p> Signup and view all the answers

    Which type of bond requires a large amount of energy for both formation and breakage according to the content provided?

    <p>Peptide bonds</p> Signup and view all the answers

    Which fatty acids predominantly occur in the human body?

    <p>Fatty acids with an even number of 16, 18, or 20 carbon atoms</p> Signup and view all the answers

    What is a common cause of rancidity in fats?

    <p>Hydrolysis leading to liberation of volatile short-chain fatty acids</p> Signup and view all the answers

    Which of the following is essential for growth and development?

    <p>Both omega-3 and omega-6 fatty acids</p> Signup and view all the answers

    What can help inhibit rancidity in lipids?

    <p>Addition of antioxidants such as vitamins A and E</p> Signup and view all the answers

    What is the primary consequence of essential fatty acid deficiency in infants?

    <p>Hair loss and low platelet count</p> Signup and view all the answers

    Which statement accurately describes the major role of dietary lipids?

    <p>To store and supply energy with a high caloric value</p> Signup and view all the answers

    How are omega-3 fatty acids characterized?

    <p>They have the terminal double bond three carbons from the omega end</p> Signup and view all the answers

    What primarily determines the types of fatty acids present in an individual's diet?

    <p>Dietary choices and nutritional intake</p> Signup and view all the answers

    What is the consequence of polar glutamate being replaced by nonpolar valine in hemoglobin A?

    <p>It causes red blood cells to deform and block blood vessels.</p> Signup and view all the answers

    What role do polar side groups in amino acids play in protein structure?

    <p>They participate in hydrogen bond formation.</p> Signup and view all the answers

    Why do amino acids behave as amphoteric substances in solution?

    <p>They contain both acidic and basic groups.</p> Signup and view all the answers

    What is the significance of the isoelectric point (IEP) in amino acids?

    <p>It is the pH at which amino acids carry equal positive and negative charges.</p> Signup and view all the answers

    What is a result of the complete ionization of neutral amino acids?

    <p>They form zwitterions with equal charges.</p> Signup and view all the answers

    Which statement best describes the role of cysteine in proteins?

    <p>It facilitates the formation of disulfide bonds.</p> Signup and view all the answers

    How do amphoteric properties contribute to the function of plasma proteins?

    <p>They enable plasma proteins to act as efficient buffers.</p> Signup and view all the answers

    What effect does the position of nonpolar R groups have on proteins in a hydrophobic environment?

    <p>They are found on the outside surface, interacting with the lipid environment.</p> Signup and view all the answers

    What is the function of disulfide bonds in proteins?

    <p>They stabilize the three-dimensional structure of proteins.</p> Signup and view all the answers

    Which of the following correctly describes high energy bonds?

    <p>They can generate over 7 kcal of energy upon hydrolysis.</p> Signup and view all the answers

    What role do unsaturated fatty acids play in human health?

    <p>They help reduce the risk of heart disease.</p> Signup and view all the answers

    What is a primary characteristic of double bonds in biological molecules?

    <p>They can exist in cis or trans configurations affecting molecular behavior.</p> Signup and view all the answers

    Which statement best describes the process of hydrogenation?

    <p>It converts double bonds in unsaturated fatty acids to single bonds.</p> Signup and view all the answers

    What occurs during the formation of phosphodiester bonds in nucleic acids?

    <p>They result from interactions between sugar carbons of nucleotides.</p> Signup and view all the answers

    What is a major biological function of disulfide bonds?

    <p>They protect proteins from oxidative damage.</p> Signup and view all the answers

    What results from the oxidation of thiol groups in cysteine residues?

    <p>Creation of disulfide bonds between cysteine residues.</p> Signup and view all the answers

    What role do enzymes play in chemical reactions regarding the energy of activation?

    <p>They lower the energy of activation, enhancing reaction rates.</p> Signup and view all the answers

    Which statement accurately describes the transition state in a chemical reaction?

    <p>It serves as the energy barrier separating reactants and products.</p> Signup and view all the answers

    How does lowering the energy of activation (Ea) affect the reaction rate?

    <p>It accelerates the reaction rate by allowing more molecules to reach the transition state.</p> Signup and view all the answers

    What is the significance of drug-induced enzyme activation in clinical settings?

    <p>It enhances the function of enzymes that are critical in emergencies, such as clot lysis.</p> Signup and view all the answers

    In what way do enzymes assist in quickening physiological processes such as digestion?

    <p>By providing alternative reaction pathways with a lower activation energy.</p> Signup and view all the answers

    Which describes the mechanism of an enzyme's interaction with its substrate to foster a reaction?

    <p>The enzyme combines transiently with the substrate, creating a lower energy state.</p> Signup and view all the answers

    What happens to the enzyme after it catalyzes a reaction?

    <p>It remains unchanged and can catalyze subsequent reactions.</p> Signup and view all the answers

    What is a primary consequence of enzymes providing lower energy activation pathways in biological systems?

    <p>They increase the likelihood of substrate molecules transitioning to products efficiently.</p> Signup and view all the answers

    What is the primary sugar derivative formed when a hydroxyl group is replaced by a hydrogen atom?

    <p>Deoxymonosaccharide</p> Signup and view all the answers

    Which of the following polysaccharides is primarily used as a storage form in plants?

    <p>Starch</p> Signup and view all the answers

    What effect does high levels of fructose have on appetite and sugar cravings?

    <p>Increases hunger and sugar cravings</p> Signup and view all the answers

    Which polysaccharide is an unbranched structural component found in plants that humans cannot digest?

    <p>Cellulose</p> Signup and view all the answers

    Which carbohydrate derivative is formed when a –CH2OH group is oxidized to –COOH?

    <p>Sugar acid</p> Signup and view all the answers

    What is the primary function of fiber in the human diet?

    <p>To aid digestion and prevent constipation</p> Signup and view all the answers

    Which component of starch is characterized by its branched structure?

    <p>Amylopectin</p> Signup and view all the answers

    What might be a consequence of consuming excessive fructose, especially for diabetics?

    <p>Increased hunger and sugar cravings</p> Signup and view all the answers

    What condition can result from the accumulation of bilirubin due to low levels of glucuronic acid in immature babies?

    <p>Kernicterus</p> Signup and view all the answers

    What is a major consequence of liver failure in relation to glucuronic acid?

    <p>Increased risk of drug toxicity</p> Signup and view all the answers

    Which of the following statements about sorbitol is true?

    <p>Excessive use can lead to digestion problems.</p> Signup and view all the answers

    How do carbohydrates generally contribute to dietary energy needs?

    <p>They are readily converted into glucose for energy.</p> Signup and view all the answers

    What health issue is primarily linked to abnormal glucose metabolism?

    <p>Diabetes Mellitus</p> Signup and view all the answers

    Which statement accurately reflects the caloric content of carbohydrates?

    <p>1 gram of carbohydrates provides 4 Calories.</p> Signup and view all the answers

    What role do carbohydrates play in relation to cell membranes?

    <p>They serve as components that mediate intercellular communication.</p> Signup and view all the answers

    What could be a consequence of inborn errors in carbohydrate metabolism?

    <p>Mental retardation</p> Signup and view all the answers

    What distinguishes amino acids from one another?

    <p>The type of R group (side chain)</p> Signup and view all the answers

    Which type of amino acids are characterized by their ability to donate protons?

    <p>Acidic amino acids</p> Signup and view all the answers

    Which of the following classifications of amino acids require dietary intake under certain physiological conditions?

    <p>Semi-essential amino acids</p> Signup and view all the answers

    What is the primary characteristic of nonpolar amino acids in a polar environment?

    <p>They cluster together to avoid water</p> Signup and view all the answers

    Which classification of amino acids includes those that can be synthesized by the body itself?

    <p>Non-essential amino acids</p> Signup and view all the answers

    What type of amino acid structure contains a benzene ring?

    <p>Aromatic amino acids</p> Signup and view all the answers

    Which group of amino acids can accept protons in aqueous solutions?

    <p>Basic amino acids</p> Signup and view all the answers

    What type of bond or interaction primarily contributes to the three-dimensional shape of proteins?

    <p>Hydrophobic interactions</p> Signup and view all the answers

    What is the primary role of reducing agents such as vitamin C and vitamin E in relation to lead exposure?

    <p>To prevent irreversible inhibition of enzymes.</p> Signup and view all the answers

    What effect does irreversible inhibition have on the maximum velocity (Vmax) of an enzymatic reaction?

    <p>It decreases Vmax.</p> Signup and view all the answers

    Which of the following describes a consequence of the irreversible inhibition by organophosphates?

    <p>Disruption of nerve signal control.</p> Signup and view all the answers

    Which plasma enzyme group is primarily associated with a specific physiological function in plasma?

    <p>Functional plasma enzymes</p> Signup and view all the answers

    What is a common outcome of diseases that cause tissue damage concerning plasma enzyme levels?

    <p>Increased release of non-functional enzymes into plasma.</p> Signup and view all the answers

    Which of the following statements accurately describes the characteristics of zymogens?

    <p>They allow enzymes to be activated at the appropriate time.</p> Signup and view all the answers

    What type of bond is primarily formed between an irreversible inhibitor and an enzyme?

    <p>Covalent bond</p> Signup and view all the answers

    Why is the presence of low doses of cyanide in cigarettes significant?

    <p>It leads to irreversible inhibition of enzymes related to ATP synthesis.</p> Signup and view all the answers

    What is the role of zymogens in the body?

    <p>To prevent auto-digestion and protect tissues from digestive enzymes.</p> Signup and view all the answers

    How can covalent modification affect enzyme activity?

    <p>By adding or removing phosphate groups to specific amino acids.</p> Signup and view all the answers

    What distinguishes allosteric enzymes from other types of enzymes?

    <p>They can bind to effectors at sites other than the active site.</p> Signup and view all the answers

    In the context of feedback inhibition, what is a 'Committed-Step Enzyme'?

    <p>The first irreversible enzyme unique to a specific pathway.</p> Signup and view all the answers

    What is a primary method by which cells regulate enzyme levels?

    <p>By altering the rate of enzyme synthesis.</p> Signup and view all the answers

    What occurs when an enzyme undergoes dephosphorylation?

    <p>The enzyme could be inactivated or activated, depending on the context.</p> Signup and view all the answers

    Which statement correctly describes the effect of positive allosteric effectors?

    <p>They increase the catalytic activity of the enzyme.</p> Signup and view all the answers

    Which of the following processes is primarily considered a long-term regulation of enzyme activity?

    <p>Enzyme synthesis alteration.</p> Signup and view all the answers

    Which factor is most likely to alter the affinity of an enzyme for its substrate?

    <p>Presence of allosteric regulators</p> Signup and view all the answers

    What describes the primary effect of competitive inhibition on enzyme kinetics?

    <p>Requires a higher substrate concentration to reach Vmax</p> Signup and view all the answers

    What is a characteristic consequence of using zymogens in enzymatic processes?

    <p>Prevention of premature digestion of proteins</p> Signup and view all the answers

    Under conditions of high substrate concentration, what primarily governs the rate of an enzyme-catalyzed reaction?

    <p>Enzyme turnover number</p> Signup and view all the answers

    Which of the following enzymes would likely show the least effect from changes in pH within the physiological range?

    <p>Carbonic anhydrase</p> Signup and view all the answers

    Which of the following fatty acids is considered essential and must be provided in the diet?

    <p>Linoleic acid</p> Signup and view all the answers

    What primarily causes the development of hydrolytic rancidity in fats?

    <p>Slight hydrolysis of fats</p> Signup and view all the answers

    Which statement about long chain fatty acids is true?

    <p>They constitute the majority of fatty acids in animal diets.</p> Signup and view all the answers

    What role do ω-3 fatty acids play in human health?

    <p>They are important for growth and development.</p> Signup and view all the answers

    Which of the following vitamins can act as an antioxidant to inhibit rancidity in fats?

    <p>Vitamin A</p> Signup and view all the answers

    What is the primary function of carbohydrates in the human body?

    <p>Providing energy and supporting cellular functions</p> Signup and view all the answers

    Which of the following accurately describes monosaccharides?

    <p>They can contain either an aldehyde or a keto group.</p> Signup and view all the answers

    What is the primary consequence of essential fatty acid deficiency in infants?

    <p>Intellectual disability</p> Signup and view all the answers

    Which property allows monosaccharides to exhibit isomerism?

    <p>Asymmetric carbon atom</p> Signup and view all the answers

    What is formed during the oxidation of unsaturated fatty acids that contributes to rancidity?

    <p>Peroxides and aldehydes</p> Signup and view all the answers

    How much energy does 1 gram of dietary lipids provide?

    <p>9 Cal</p> Signup and view all the answers

    What is maltose commonly known as?

    <p>Malt sugar</p> Signup and view all the answers

    Which of the following statements about lactose is true?

    <p>It is a disaccharide made of glucose and galactose.</p> Signup and view all the answers

    Which carbohydrate serves as the only source of galactose in human diet?

    <p>Lactose</p> Signup and view all the answers

    What distinguishes polysaccharides from other types of carbohydrates?

    <p>They consist of more than ten monosaccharide units.</p> Signup and view all the answers

    What condition can result from lactose intolerance?

    <p>Digestive issues such as gas and bloating</p> Signup and view all the answers

    What is the role of an enzyme in a chemical reaction?

    <p>To lower the free energy of activation</p> Signup and view all the answers

    What characterizes the transition state (T*) during a chemical reaction?

    <p>It has a high probability for making or breaking chemical bonds</p> Signup and view all the answers

    Why is the energy of activation (Ea) important in the context of enzymatic reactions?

    <p>It dictates how many substrate molecules can interact</p> Signup and view all the answers

    What happens to the reaction rate when the activation energy is decreased by an enzyme?

    <p>The reaction rate increases</p> Signup and view all the answers

    How do enzymes facilitate the process of catalysis?

    <p>By providing an alternative reaction pathway with lower Ea</p> Signup and view all the answers

    What is one primary clinical application of enzymes discussed?

    <p>To activate tissue plasminogen for clot lysis</p> Signup and view all the answers

    Which statement best describes the relationship between enzyme concentration and the rate of reaction when substrate is in excess?

    <p>The reaction rate increases linearly with enzyme concentration</p> Signup and view all the answers

    Why are enzymes considered important in biochemical reactions in the body?

    <p>They allow reactions to occur at a useful rate</p> Signup and view all the answers

    What term is used for substances that decrease the expression of gene coding for enzymes?

    <p>Repressors</p> Signup and view all the answers

    What happens to the apparent Km of an enzyme when a competitive inhibitor is present?

    <p>It increases</p> Signup and view all the answers

    Which characteristic distinguishes non-competitive inhibition from competitive inhibition?

    <p>Decreases Vmax</p> Signup and view all the answers

    What is the effect of increasing substrate concentration in the presence of a competitive inhibitor?

    <p>Inhibition can be overcome</p> Signup and view all the answers

    What type of inhibition occurs when the inhibitor binds at a different site from the substrate-binding site?

    <p>Non-competitive inhibition</p> Signup and view all the answers

    In non-competitive inhibition, how does the presence of the inhibitor affect the Km of the enzyme?

    <p>It does not change the Km</p> Signup and view all the answers

    Why are statin drugs considered competitive inhibitors in cholesterol biosynthesis?

    <p>They resemble the natural substrate</p> Signup and view all the answers

    What type of complex is formed at the active site of the enzyme during competitive inhibition?

    <p>EI complex</p> Signup and view all the answers

    What is the role of zymogens in physiological processes?

    <p>They protect tissues from auto-digestion and coagulation.</p> Signup and view all the answers

    Which statement about covalent modification of enzymes is accurate?

    <p>Phosphorylation and dephosphorylation lead to two inter-convertible active forms of an enzyme.</p> Signup and view all the answers

    What differentiates allosteric enzymes from regular enzymes?

    <p>They change their shape upon binding to effectors at allosteric sites.</p> Signup and view all the answers

    What is the process called when end products inhibit the activity of an enzyme?

    <p>Feedback inhibition</p> Signup and view all the answers

    How does increased enzyme synthesis affect enzyme activity?

    <p>It allows for long-term regulation of enzyme concentrations.</p> Signup and view all the answers

    Which type of enzyme regulation occurs rapidly, usually within seconds to minutes?

    <p>Covalent modification</p> Signup and view all the answers

    Which scenario describes the impact of elevated insulin levels on enzyme synthesis?

    <p>It induces the synthesis of key enzymes for glucose metabolism.</p> Signup and view all the answers

    Which statement is true regarding positive and negative effectors in allosteric modulation?

    <p>Positive effectors enhance the enzyme's activity.</p> Signup and view all the answers

    Which type of fatty acids predominantly contain double bonds in a cis configuration?

    <p>Unsaturated fatty acids</p> Signup and view all the answers

    What effect does the addition of double bonds generally have on the melting temperature (Tm) of fatty acids?

    <p>It decreases the melting temperature.</p> Signup and view all the answers

    Which chain lengths classify as short-chain fatty acids?

    <p>2 to 6 carbon atoms</p> Signup and view all the answers

    What is primarily a benefit of medium-chain fatty acids in the diet?

    <p>They improve gut health.</p> Signup and view all the answers

    What is a characteristic of trans fatty acids compared to cis fatty acids?

    <p>They are associated with a higher risk of atherosclerosis.</p> Signup and view all the answers

    Which of the following fatty acids is classified as having 7 to 12 carbon atoms?

    <p>Capric acid</p> Signup and view all the answers

    How does the presence of double bonds influence the fluidity of membrane lipids?

    <p>It promotes the fluid nature of the lipids.</p> Signup and view all the answers

    What is a common source of medium-chain fatty acids?

    <p>Coconut oil</p> Signup and view all the answers

    What is the significance of high energy bonds in ATP?

    <p>They are broken to yield energy for metabolic processes.</p> Signup and view all the answers

    Which type of bond involves the transfer of an electron?

    <p>Ionic bond</p> Signup and view all the answers

    Which of the following compounds is NOT considered a high energy compound?

    <p>Glucose</p> Signup and view all the answers

    What role do hydrogen bonds play in molecular interactions?

    <p>They facilitate weak electrostatic attractions between molecules.</p> Signup and view all the answers

    What is the primary effect of ionic bonds on protein structure?

    <p>They stabilize tertiary and quaternary structures.</p> Signup and view all the answers

    Which of the following is a characteristic of non-covalent bonds?

    <p>They include bond types such as ionic and hydrogen bonds.</p> Signup and view all the answers

    What is a primary role of hydrogen bonds in DNA structure?

    <p>They stabilize the double helix by connecting base pairs.</p> Signup and view all the answers

    Why are enzymes important for metabolic reactions in the human body?

    <p>They speed up reactions that would otherwise be too slow.</p> Signup and view all the answers

    Which compound mentioned here is used primarily as an energy currency in the body?

    <p>ATP</p> Signup and view all the answers

    What must occur for a hydrogen bond to form?

    <p>A hydrogen atom must be attached to an electronegative atom.</p> Signup and view all the answers

    What distinguishes a holoenzyme from a simple enzyme?

    <p>A holoenzyme includes both protein and non-protein components.</p> Signup and view all the answers

    What type of interactions occur between charged atoms that can be either repulsive or attractive?

    <p>Electrostatic interactions.</p> Signup and view all the answers

    What is necessary for DNA replication to occur?

    <p>Breaking of hydrogen bonds between base pairs.</p> Signup and view all the answers

    What is a simple enzyme composed of?

    <p>Only protein molecules with no non-protein components.</p> Signup and view all the answers

    How do enzymes affect the energy barrier of chemical reactions?

    <p>They lower the energy barrier and speed up the reaction.</p> Signup and view all the answers

    What type of bond is primarily responsible for the 3D structure of proteins?

    <p>Hydrogen bonds.</p> Signup and view all the answers

    What is the optimum temperature for most human enzymes?

    <p>37°C</p> Signup and view all the answers

    Which factor leads to a decrease in enzyme activity beyond its optimal temperature?

    <p>Temperature-induced denaturation</p> Signup and view all the answers

    What is a characteristic of pH that affects enzyme activity?

    <p>Enzyme activity can require specific protonation states.</p> Signup and view all the answers

    Which statement regarding enzyme activity and temperature is true?

    <p>Enzyme activity is reduced at low temperatures but increases steadily as temperature rises.</p> Signup and view all the answers

    What identifies the pH at which an enzyme is most active?

    <p>Optimum pH</p> Signup and view all the answers

    What might be a life-threatening condition related to enzyme function?

    <p>Extreme hypothermia or fever</p> Signup and view all the answers

    How does the proton concentration in an acidic medium affect enzyme activity?

    <p>It can enhance activity by facilitating the enzyme-substrate interaction.</p> Signup and view all the answers

    Which enzyme is mentioned as maximally active at a low pH range?

    <p>Pepsin</p> Signup and view all the answers

    What is the term for a non-protein component that is tightly bound to an apoenzyme and difficult to remove?

    <p>Prosthetic group</p> Signup and view all the answers

    How do isoenzymes differ from one another?

    <p>They have different physical and chemical characteristics.</p> Signup and view all the answers

    What defines the rate limiting step in an enzymatic reaction?

    <p>It sets the pace for the entire reaction.</p> Signup and view all the answers

    What model describes the enzyme-substrate interaction, emphasizing flexibility in binding?

    <p>Induced-fit model</p> Signup and view all the answers

    Which ions can serve as inorganic cofactors for enzymes?

    <p>Fe2+ and Mn2+</p> Signup and view all the answers

    What term describes the molecule or reactant that an enzyme acts upon?

    <p>Substrate</p> Signup and view all the answers

    Which characteristic best defines isoenzymes?

    <p>Same substrate but different sites of origin</p> Signup and view all the answers

    What does the active site of an enzyme do?

    <p>Facilitates non-covalent interactions for substrate binding.</p> Signup and view all the answers

    What condition can occur due to a severe deficiency of glutamine?

    <p>Convulsions</p> Signup and view all the answers

    Which amino acid is a precursor for the production of melanin?

    <p>Tyrosine</p> Signup and view all the answers

    What serious outcome can result from the defect in insulin production?

    <p>Diabetes mellitus</p> Signup and view all the answers

    What can excessive intake of amino acids lead to in athletes?

    <p>Kidney failure</p> Signup and view all the answers

    Which of the following is a potential consequence of defects in structural proteins like collagen?

    <p>Changes in skin elasticity</p> Signup and view all the answers

    What is the role of hydroxy-containing amino acids in the body?

    <p>Signal transduction</p> Signup and view all the answers

    Which phenomenon can arise due to inborn errors of amino acid metabolism?

    <p>Mental retardation</p> Signup and view all the answers

    What can deposition of abnormal proteins cause?

    <p>Alzheimer's disease</p> Signup and view all the answers

    What distinguishes the side chains of amino acids?

    <p>They determine the amino acid's unique chemical properties.</p> Signup and view all the answers

    Which type of amino acid can donate a proton at physiological pH?

    <p>Acidic amino acid</p> Signup and view all the answers

    Which classification of amino acids refers to those that must be obtained through diet?

    <p>Essential amino acids</p> Signup and view all the answers

    What is the primary characteristic of nonpolar amino acids in an aqueous environment?

    <p>They are less soluble in water.</p> Signup and view all the answers

    Which of the following amino acids contains a sulfur group in its side chain?

    <p>Cysteine</p> Signup and view all the answers

    What type of side chain do polar amino acids have?

    <p>They can participate in hydrogen or ionic bonds.</p> Signup and view all the answers

    What structural feature is common to all amino acids?

    <p>A central carbon atom bonded to four different groups.</p> Signup and view all the answers

    What phenomenon primarily contributes to the three-dimensional shape of proteins involving nonpolar amino acids?

    <p>The hydrophobic effect</p> Signup and view all the answers

    What type of bond is formed when one atom gains an electron and another loses an electron?

    <p>Ionic bond</p> Signup and view all the answers

    Which of the following correctly describes high energy bonds found in ATP?

    <p>They are phosphoric anhydride bonds.</p> Signup and view all the answers

    What is a significant role of ionic bonds in biological systems?

    <p>Protein folding and stability</p> Signup and view all the answers

    Among the following compounds, which is classified as a high energy compound due to its high energy bonds?

    <p>Creatine phosphate</p> Signup and view all the answers

    Which statement is true regarding hydrogen bonds compared to ionic bonds?

    <p>Hydrogen bonds are generally weaker than ionic bonds.</p> Signup and view all the answers

    What characterizes the majority of high energy compounds, excluding ATP?

    <p>Involvement of phosphorus</p> Signup and view all the answers

    In which type of bond does the attraction occur due to the proximity of a hydrogen atom bonded to electronegative atoms?

    <p>Hydrogen bond</p> Signup and view all the answers

    What is the role of hydrogen bonds in DNA structure?

    <p>They stabilize the double helix by bonding nucleotide bases.</p> Signup and view all the answers

    What feature distinguishes non-covalent bonds from covalent bonds?

    <p>Non-covalent bonds are generally reversible.</p> Signup and view all the answers

    Which of the following statements about enzyme function is correct?

    <p>Enzymes increase the rate of biological reactions by lowering the energy barrier.</p> Signup and view all the answers

    What distinguishes a holoenzyme from a simple enzyme?

    <p>A holoenzyme cannot function without a coenzyme.</p> Signup and view all the answers

    Which statement correctly describes electrostatic interactions in proteins?

    <p>They influence the three-dimensional structure of proteins.</p> Signup and view all the answers

    How do high energy barriers affect enzymatic reactions?

    <p>They slow down reactions unless enzymes lower the barrier.</p> Signup and view all the answers

    Which factor is critical for the specificity of enzyme activity?

    <p>The nature of the substrate aligns with the enzyme's active site.</p> Signup and view all the answers

    Why are hydrogen bonds crucial for protein folding?

    <p>They help maintain the overall shape of proteins.</p> Signup and view all the answers

    What is an essential characteristic of enzymes as catalysts?

    <p>They do not change during the reactions they catalyze.</p> Signup and view all the answers

    What is the primary distinction between competitive and non-competitive inhibitors in enzyme reactions?

    <p>Competitive inhibitors reduce enzyme-substrate affinity, while non-competitive inhibitors do not affect substrate binding.</p> Signup and view all the answers

    In the presence of a competitive inhibitor, which of the following is true regarding the enzyme's behavior?

    <p>The Km of the enzyme increases, indicating decreased substrate affinity.</p> Signup and view all the answers

    What is a clinical implication of competitive inhibition in the context of statin drugs?

    <p>Statin drugs compete with the natural substrate, reducing cholesterol synthesis rates.</p> Signup and view all the answers

    Which of the following characterizes non-competitive inhibition?

    <p>It lowers the Vmax of the enzyme but does not affect the Km.</p> Signup and view all the answers

    Why might non-competitive inhibitors be considered important in metabolic pathways?

    <p>They can help regulate enzyme activity without affecting substrate affinity.</p> Signup and view all the answers

    What happens to the catalytic activity of an enzyme when a non-competitive inhibitor is introduced?

    <p>The maximum reaction rate (Vmax) decreases, but the affinity for the substrate remains unchanged.</p> Signup and view all the answers

    Which of the following statements regarding inhibitors is correct?

    <p>Inhibitors can have varying effects depending on their mechanism of action.</p> Signup and view all the answers

    What occurs to the enzyme-inhibitor complex (EI) formed during competitive inhibition?

    <p>It prevents the formation of the enzyme-substrate complex.</p> Signup and view all the answers

    What is the primary temperature at which human enzymes exhibit maximal activity?

    <p>37°C</p> Signup and view all the answers

    Which of the following statements correctly describes the effect of pH on enzyme activity?

    <p>Optimal pH varies significantly among different enzymes.</p> Signup and view all the answers

    What happens to enzyme activity at temperatures exceeding the optimum level?

    <p>Enzyme activity decreases due to denaturation.</p> Signup and view all the answers

    Which type of medium is pepsin most active in?

    <p>Acidic medium (pH 1-2)</p> Signup and view all the answers

    How does increasing the concentration of protons affect a catalytic process?

    <p>Protons can switch the activity state of enzyme groups.</p> Signup and view all the answers

    Which class of carbohydrates consists of 2 to 10 monosaccharide units?

    <p>Oligosaccharides</p> Signup and view all the answers

    What is the common characteristic of all monosaccharides regarding their chemical composition?

    <p>They have a general molecular formula of CnH2nOn.</p> Signup and view all the answers

    Which disaccharide is specifically identified as being derived from starch?

    <p>Maltose</p> Signup and view all the answers

    What role does lactose play in the absorption of minerals?

    <p>It assists in the absorption of minerals like calcium, copper, and zinc.</p> Signup and view all the answers

    How are monosaccharides classified based on their carbon atom counts?

    <p>They depend on the number of carbon atoms present.</p> Signup and view all the answers

    What distinguishes aldoses from ketoses?

    <p>Aldoses have a carbonyl group at the end of the carbon chain.</p> Signup and view all the answers

    Which type of carbohydrate is the sole source of galactose in the diet?

    <p>Lactose</p> Signup and view all the answers

    What phenomenon allows monosaccharides to exist in multiple structural forms?

    <p>Asymmetry of carbon atoms</p> Signup and view all the answers

    What is the primary consequence of excessive carbohydrate ingestion?

    <p>Weight gain leading to obesity</p> Signup and view all the answers

    Which of the following statements is true regarding simple lipids?

    <p>They include esters of fatty acids with glycerol.</p> Signup and view all the answers

    Which type of complex lipid is composed of a fatty acid, sphingosine, and carbohydrate residues?

    <p>Glycolipids</p> Signup and view all the answers

    What property of fatty acids allows them to have both hydrophilic and hydrophobic characteristics?

    <p>Ionization of the terminal carboxyl group</p> Signup and view all the answers

    What defines triacylglycerols in terms of structure?

    <p>Three fatty acids linked to glycerol</p> Signup and view all the answers

    Which component is NOT a structural feature of complex lipids?

    <p>High molecular weight alcohols</p> Signup and view all the answers

    Which types of vitamins are classified as fat-soluble?

    <p>Vitamins A, D, E, and K</p> Signup and view all the answers

    What determines whether a glycosidic bond is classified as α or β?

    <p>The position of the hydroxyl group during formation</p> Signup and view all the answers

    Which type of bond provides the primary structure of proteins?

    <p>Peptide bonds</p> Signup and view all the answers

    What action characterizes a wax in the context of lipid classification?

    <p>High molecular weight alcohols and fatty acids</p> Signup and view all the answers

    Which statement accurately describes the bond formed during esterification?

    <p>It forms between the hydroxyl group of an alcohol and the carboxylic group of an acid.</p> Signup and view all the answers

    What is the general composition of lipids?

    <p>C, H, O, and other elements like P, N, and S</p> Signup and view all the answers

    What type of lipid is primarily responsible for instilling structure in cell membranes?

    <p>Phospholipids</p> Signup and view all the answers

    What is the primary reason maltose can be digested in the body while cellulose cannot?

    <p>Maltose contains α bonds, while cellulose contains β bonds.</p> Signup and view all the answers

    What role do esterase enzymes play in the body?

    <p>They break down ester bonds to terminate nerve impulses.</p> Signup and view all the answers

    What distinguishes a peptide bond from other types of chemical bonds?

    <p>It involves an amino group and a carboxylic group.</p> Signup and view all the answers

    How does the position of the glycosidic bond in glycans influence metabolism?

    <p>It determines the type of enzyme that can metabolize the molecule.</p> Signup and view all the answers

    What is one of the strongest types of covalent bond found in biomolecules?

    <p>Peptide bond</p> Signup and view all the answers

    Which of the following best describes the role of acetylcholinesterase in the nervous system?

    <p>It breaks down acetylcholine to terminate nerve signals.</p> Signup and view all the answers

    Which of the following statements correctly describes the function of proteins in the body?

    <p>Proteins can regulate metabolic processes, provide structural support, and transport essential molecules.</p> Signup and view all the answers

    What is the primary consequence of disruptions in lipid levels within the body?

    <p>Increased risk of diseases such as obesity and diabetes.</p> Signup and view all the answers

    Which of the following correctly characterizes amino acids?

    <p>There are 20 naturally occurring amino acids used to synthesize proteins.</p> Signup and view all the answers

    What role do proteins such as immunoglobulins play in the body?

    <p>Fighting infectious bacteria and viruses.</p> Signup and view all the answers

    Which statement about the peptide bond is correct?

    <p>It is formed between amino acids through their amino and carboxylic groups.</p> Signup and view all the answers

    Which function do contractile proteins perform in the body?

    <p>Facilitate movement.</p> Signup and view all the answers

    What can be a potential outcome of excessive dietary intake of lipids?

    <p>Increased risk of developing metabolic disorders.</p> Signup and view all the answers

    In which way do amino acids contribute to cellular signaling?

    <p>They act as secondary messengers.</p> Signup and view all the answers

    What structural role do proteins such as collagen play in the body?

    <p>They form the foundation for calcium deposits in bones.</p> Signup and view all the answers

    Which statement best captures the significance of fat-soluble vitamins and their relationship with lipids?

    <p>Lipids help in the solubilization and transport of fat-soluble vitamins.</p> Signup and view all the answers

    What is the primary characteristic of saturated fatty acids?

    <p>They contain no double bonds.</p> Signup and view all the answers

    Which type of fatty acid is associated with an increased risk of atherosclerosis?

    <p>Saturated fatty acids</p> Signup and view all the answers

    How does the presence of double bonds affect the melting temperature of fatty acids?

    <p>It decreases the melting temperature.</p> Signup and view all the answers

    Which statement describes the role of medium chain fatty acids (MCFA) in dietary practices?

    <p>They help maintain gut health without harming beneficial bacteria.</p> Signup and view all the answers

    What configuration do natural fatty acids typically have with regard to their double bonds?

    <p>Cis configuration, with functional groups on the same side.</p> Signup and view all the answers

    What chain length defines medium chain fatty acids (MCFA)?

    <p>7-12 carbon atoms.</p> Signup and view all the answers

    Which of the following fatty acids is primarily derived from coconut oil?

    <p>Medium chain fatty acids</p> Signup and view all the answers

    What condition occurs due to the predominance of trans fatty acids in artificial foods?

    <p>Increased risk of atherosclerosis</p> Signup and view all the answers

    What role do polar amino acids play in stabilizing protein structure?

    <p>They participate in hydrogen bond formation.</p> Signup and view all the answers

    What specific property of amino acids allows them to act as both acids and bases?

    <p>The existence of both an acidic group (-COOH) and a basic group (-NH2).</p> Signup and view all the answers

    What happens to amino acids at their isoelectric point (IEP)?

    <p>They remain neutral, without migrating towards the electrodes.</p> Signup and view all the answers

    How does the mutation responsible for sickle cell anemia affect hemoglobin structure?

    <p>It results in the replacement of polar glutamate with nonpolar valine.</p> Signup and view all the answers

    What clinical significance does the side chain of cysteine have?

    <p>It contributes to the formation of disulfide bonds which stabilize protein structure.</p> Signup and view all the answers

    What characterizes the distribution of nonpolar R groups in proteins located in hydrophobic environments, such as membranes?

    <p>They cluster together in the inner core of the protein, shielded from the lipid layers.</p> Signup and view all the answers

    What is the main function of plasma proteins being amphoteric?

    <p>To maintain the pH of the blood through buffering.</p> Signup and view all the answers

    What can be inferred about the ionization state of amino acids in solution at a pH lower than their isoelectric point?

    <p>They predominantly carry a positive charge.</p> Signup and view all the answers

    What role do lipids play in cellular response pathways?

    <p>They function as signalling molecules.</p> Signup and view all the answers

    How do abnormal lipid levels affect health?

    <p>They are linked to several diseases including obesity and diabetes.</p> Signup and view all the answers

    What characterizes the structure of amino acids?

    <p>They consist of a carboxylic group, an amino group, and a variable side chain.</p> Signup and view all the answers

    What bond is formed between amino acids during protein synthesis?

    <p>Peptide bond.</p> Signup and view all the answers

    What is the primary reason for the formation of chemical bonds between atoms?

    <p>To achieve the most stable, lowest-energy state.</p> Signup and view all the answers

    Which of the following statements is true regarding proteins and their roles in transport?

    <p>Hemoglobin and albumin are proteins that transport essential molecules.</p> Signup and view all the answers

    Which protein is primarily responsible for providing a structural framework in bone?

    <p>Collagen.</p> Signup and view all the answers

    Which type of bond is formed when electrons are shared unequally between two different atoms?

    <p>Polar covalent bond</p> Signup and view all the answers

    Which function is NOT attributed to proteins in the body?

    <p>Acting exclusively as energy reserves.</p> Signup and view all the answers

    What defines a nonpolar covalent bond?

    <p>Sharing of electrons equally between atoms.</p> Signup and view all the answers

    What is the significance of essential amino acids in human diet?

    <p>They must be obtained through dietary sources for proper function.</p> Signup and view all the answers

    Which statement best describes the property of covalent bonds in terms of strength?

    <p>Covalent bonds are stronger than non-covalent bonds.</p> Signup and view all the answers

    Which type of bond is typically involved in linking macromolecular building blocks?

    <p>Covalent bonds</p> Signup and view all the answers

    In the context of covalent bonds, which scenario demonstrates the octet rule?

    <p>Two atoms share a pair of electrons to achieve eight in their outer shell.</p> Signup and view all the answers

    Which example represents a polar covalent bond?

    <p>Water (H2O)</p> Signup and view all the answers

    What occurs when atoms do not satisfy the octet rule?

    <p>Atoms remain unstable and seek to gain, lose, or share electrons.</p> Signup and view all the answers

    What occurs when enzyme concentration increases beyond a certain point while substrate concentration remains unlimited?

    <p>The reaction rate plateaus and does not increase further.</p> Signup and view all the answers

    Which of the following statements accurately describes the behavior of an enzyme in first-order kinetics?

    <p>The reaction velocity is directly proportional to the substrate concentration.</p> Signup and view all the answers

    What is a key characteristic of zymogens in enzymatic activity?

    <p>They can be irreversibly activated after hydrolysis.</p> Signup and view all the answers

    Which factor is most likely to decrease enzyme activity as the reaction progresses?

    <p>Accumulation of product.</p> Signup and view all the answers

    What defines a zero-order reaction in enzymatic kinetics?

    <p>The reaction rate is constant and independent of substrate concentration.</p> Signup and view all the answers

    Which enzyme variant is characterized by having a high Km value and functions in the liver?

    <p>Glucokinase</p> Signup and view all the answers

    How does increasing product concentration impact an allosteric enzyme?

    <p>It typically decreases enzyme activity.</p> Signup and view all the answers

    What happens to enzyme activity when the substrate concentration is much greater than Km?

    <p>The velocity stabilizes at Vmax, and is no longer affected by substrate concentration.</p> Signup and view all the answers

    What is the general molecular formula for carbohydrates?

    <p>(CH2O)n, where n &gt; 3</p> Signup and view all the answers

    Which type of carbohydrate is composed of 2 to 10 monosaccharide units?

    <p>Oligosaccharides</p> Signup and view all the answers

    What are the most abundant monosaccharides in nature?

    <p>Hexoses</p> Signup and view all the answers

    Which sugar is referred to as milk sugar?

    <p>Lactose</p> Signup and view all the answers

    What health condition is characterized by difficulty digesting lactose?

    <p>Lactose Intolerance</p> Signup and view all the answers

    Which disaccharide consists of glucose and fructose?

    <p>Sucrose</p> Signup and view all the answers

    Which of the following carbohydrate types can contribute to health issues such as diabetes when consumed excessively?

    <p>Monosaccharides</p> Signup and view all the answers

    What is the primary role of galactose in the body?

    <p>Integral role in neural processes</p> Signup and view all the answers

    What distinguishes each amino acid chemically?

    <p>R group (side chain)</p> Signup and view all the answers

    Which class of amino acids can be synthesized by the body and therefore are not essential in the diet?

    <p>Non-essential amino acids</p> Signup and view all the answers

    Which type of amino acids tend to cluster together in the interior of proteins in aqueous solutions?

    <p>Nonpolar amino acids</p> Signup and view all the answers

    Which category includes amino acids that can donate a hydrogen and carry a negative charge at physiological pH?

    <p>Acidic amino acids</p> Signup and view all the answers

    What is the classification of amino acids based on their side chain's ability to engage in hydrogen or ionic bonding?

    <p>Polar and nonpolar</p> Signup and view all the answers

    Which amino acids are specifically identified as containing a sulfur group in their side chains?

    <p>Methionine and cysteine</p> Signup and view all the answers

    Which of the following classifications is NOT commonly used for amino acids?

    <p>By color</p> Signup and view all the answers

    What phenomenon helps give proteins their three-dimensional shape due to the clustering of nonpolar amino acids in a polar environment?

    <p>Hydrophobic effect</p> Signup and view all the answers

    What is the effect of temperature on enzyme activity?

    <p>Enzyme activity increases until a peak is reached, followed by a decline.</p> Signup and view all the answers

    What is the optimum pH for pepsin enzyme activity?

    <p>pH 1-2</p> Signup and view all the answers

    Which of the following factors primarily affects the catalytic activity of enzymes?

    <p>pH levels and temperature conditions</p> Signup and view all the answers

    What occurs to an enzyme when exposed to a temperature above its optimum range?

    <p>The enzyme experiences denaturation, reducing activity.</p> Signup and view all the answers

    How does a decrease in temperature affect enzyme activity?

    <p>Enzyme activity decreases due to reduced kinetic energy.</p> Signup and view all the answers

    What defines the ‘optimum temperature’ for most human enzymes?

    <p>The temperature at which maximal enzyme activity is observed.</p> Signup and view all the answers

    Which statement best describes the relationship between enzyme activity and pH?

    <p>Every enzyme has a specific pH range impacting its activity.</p> Signup and view all the answers

    What could result from a condition causing extreme hypothermia in the body concerning enzyme activity?

    <p>Complete enzyme inactivity.</p> Signup and view all the answers

    What is a characteristic of high energy bonds in ATP?

    <p>They are represented by the symbol ‘~’ and drive metabolic processes.</p> Signup and view all the answers

    Which of the following compounds is NOT classified as a high energy compound?

    <p>Urea</p> Signup and view all the answers

    What type of bond is primarily responsible for protein folding?

    <p>Ionic bonds</p> Signup and view all the answers

    What occurs in ionic bonding?

    <p>Electrons are transferred between atoms, resulting in charged ions.</p> Signup and view all the answers

    Which statement is true about hydrogen bonds?

    <p>They involve a hydrogen atom bonded to an electronegative atom.</p> Signup and view all the answers

    What is the main function of ATP in metabolism?

    <p>It provides energy through the breakdown of high energy bonds.</p> Signup and view all the answers

    What distinguishes non-covalent bonds from covalent bonds?

    <p>Non-covalent bonds are typically reversible interactions.</p> Signup and view all the answers

    Which bond type is usually found in dry forms such as salts?

    <p>Ionic bonds</p> Signup and view all the answers

    What is the significance of disulfide bonds in proteins?

    <p>They stabilize protein folding and protect against oxidative damage.</p> Signup and view all the answers

    Which of the following describes a high energy bond?

    <p>A bond whose hydrolysis releases more than 7 kcal of energy.</p> Signup and view all the answers

    What is the biological role of unsaturated fatty acids in diet?

    <p>They help reduce the risk of heart disease.</p> Signup and view all the answers

    What happens during the hydrogenation of vegetable oils?

    <p>Unsaturated fats are converted to saturated fats.</p> Signup and view all the answers

    Which statement is true regarding phosphodiester bonds?

    <p>They connect the sugar carbons of nucleotides in nucleic acids.</p> Signup and view all the answers

    What characterizes a double bond in chemistry?

    <p>The sharing of two pairs of electrons between atoms.</p> Signup and view all the answers

    What is the outcome of oxidative damage prevention by disulfide bonds?

    <p>It facilitates enzyme catalysis and folding.</p> Signup and view all the answers

    How are high energy compounds important in metabolism?

    <p>They store and transfer energy for cellular processes.</p> Signup and view all the answers

    What property allows amino acids to behave as acids and alkalis in solution?

    <p>Amphoteric property</p> Signup and view all the answers

    What is the significance of the polar side groups in amino acids?

    <p>They participate in hydrogen bond formation.</p> Signup and view all the answers

    What change occurs in hemoglobin that leads to sickle cell anemia?

    <p>A nonpolar amino acid replaces a polar amino acid.</p> Signup and view all the answers

    At what pH does an amino acid carry equal positive and negative charges?

    <p>Isoelectric point (IEP)</p> Signup and view all the answers

    Which amino acid side chain is crucial for disulfide bond formation?

    <p>Cysteine</p> Signup and view all the answers

    How do plasma proteins utilize their amphoteric properties?

    <p>To maintain the pH of the blood.</p> Signup and view all the answers

    What occurs to amino acids at their isoelectric point when an electric current is applied?

    <p>They precipitate in place.</p> Signup and view all the answers

    Which of these amino acids is likely involved in the active site of many enzymes?

    <p>Cysteine</p> Signup and view all the answers

    Which fatty acid predominates in the human body?

    <p>Fatty acids with an even number of carbon atoms</p> Signup and view all the answers

    What type of rancidity is primarily caused by the oxidation of unsaturated fatty acids?

    <p>Oxidative rancidity</p> Signup and view all the answers

    Which of the following is an essential fatty acid that must be provided in the diet?

    <p>Linoleic acid</p> Signup and view all the answers

    What is a common sign of essential fatty acid deficiency in infants?

    <p>Hair loss</p> Signup and view all the answers

    What role do antioxidants play in preventing rancidity?

    <p>They inhibit oxidation of unsaturated fatty acids</p> Signup and view all the answers

    In which type of food are ω-3 fatty acids predominantly found?

    <p>Sardines</p> Signup and view all the answers

    How much energy does 1 gram of dietary lipids provide?

    <p>9 Cal</p> Signup and view all the answers

    What is one way to inhibit rancidity in lipids?

    <p>Keep fats in a cold, clean place away from light</p> Signup and view all the answers

    What role do lipids play in the body's function?

    <p>They function as signalling molecules and aid in the transport of fat-soluble vitamins.</p> Signup and view all the answers

    What is the consequence of abnormal lipid metabolism in the body?

    <p>It can contribute to diseases such as obesity and diabetes.</p> Signup and view all the answers

    What are the building blocks of proteins?

    <p>Amino acids</p> Signup and view all the answers

    Which type of protein is directly involved in muscle movement?

    <p>Contractile proteins</p> Signup and view all the answers

    How are amino acids linked together to form proteins?

    <p>By peptide bonds</p> Signup and view all the answers

    What essential function do proteins perform in the bloodstream?

    <p>They transport essential molecules and fight infections.</p> Signup and view all the answers

    Which of the following is NOT a role of proteins in the body?

    <p>Providing insulation and energy storage</p> Signup and view all the answers

    What is a secondary messenger in cellular signalling?

    <p>A molecule that transmits signals inside cells</p> Signup and view all the answers

    What happens when an enzyme's active sites become fully occupied?

    <p>The enzyme reaches its maximal velocity.</p> Signup and view all the answers

    What does a high Km value indicate about an enzyme's affinity for its substrate?

    <p>The enzyme has a low affinity for the substrate.</p> Signup and view all the answers

    At what point does increasing substrate concentration no longer affect the reaction rate?

    <p>When active sites are fully saturated.</p> Signup and view all the answers

    What physiological change can lead to decreased function of the pepsin enzyme?

    <p>Aging and surgeries altering pH levels.</p> Signup and view all the answers

    Which factor does NOT affect enzyme activity?

    <p>Physical appearance of the substrate.</p> Signup and view all the answers

    What is the result of a low substrate concentration in relation to enzyme kinetics?

    <p>The enzyme operates under first-order kinetics.</p> Signup and view all the answers

    Which of the following statements is true regarding the effect of pH on enzyme activity?

    <p>Extreme pH can lead to enzyme denaturation.</p> Signup and view all the answers

    What characteristic of an enzyme does Km provide insight into?

    <p>The enzyme's affinity for substrate.</p> Signup and view all the answers

    What term is used to describe substances that increase the expression of the gene coding for an enzyme?

    <p>Inducers</p> Signup and view all the answers

    Which characteristic defines competitive inhibition of enzymes?

    <p>Inhibitor must resemble the substrate structurally</p> Signup and view all the answers

    What effect does non-competitive inhibition have on the maximum velocity (Vmax) of an enzyme?

    <p>Decreases Vmax</p> Signup and view all the answers

    What type of complex is formed when a competitive inhibitor binds to an enzyme?

    <p>EI complex</p> Signup and view all the answers

    How does non-competitive inhibition affect the apparent Km of an enzyme?

    <p>No change in Km</p> Signup and view all the answers

    In competitive inhibition, what happens to the enzyme activity when substrate concentration is increased?

    <p>Inhibition can be overcome</p> Signup and view all the answers

    What distinguishes non-competitive inhibitors from competitive inhibitors?

    <p>Location of binding site on the enzyme</p> Signup and view all the answers

    Which mechanism describes how statin drugs function as inhibitors?

    <p>Competitive inhibition by binding to the active site</p> Signup and view all the answers

    What type of lipids includes esters of fatty acids with glycerol that can have one, two, or three fatty acids attached?

    <p>Simple lipids</p> Signup and view all the answers

    Which fatty acids possess an amphipathic nature due to the presence of a carboxyl group?

    <p>All fatty acids</p> Signup and view all the answers

    What are lipids primarily characterized by regarding their solubility in solvents?

    <p>They are relatively insoluble in water but soluble in nonpolar solvents.</p> Signup and view all the answers

    Which of the following types of lipids includes sphingosine and carbohydrate residues in their structure?

    <p>Glycolipids</p> Signup and view all the answers

    What is the consequence of excessive carbohydrate ingestion on digestive health?

    <p>Increased risk of obesity and related diseases</p> Signup and view all the answers

    Which group of organic compounds includes fatty acids with variable structures and properties?

    <p>Lipids</p> Signup and view all the answers

    Which type of lipids are considered hydrolytic products of both simple and complex lipids?

    <p>Derived lipids</p> Signup and view all the answers

    What type of lipid is characterized by the presence of high molecular weight alcohols esterified with fatty acids?

    <p>Waxes</p> Signup and view all the answers

    What primarily drives the metabolic processes of life through energy release?

    <p>High energy bonds</p> Signup and view all the answers

    Which of the following correctly describes phosphoric anhydride bonds?

    <p>They occur between phosphate groups in ATP.</p> Signup and view all the answers

    What is NOT a function of proteins in the body?

    <p>Store energy for long-term use</p> Signup and view all the answers

    What type of bond involves the transfer of an electron resulting in charged ions?

    <p>Ionic bond</p> Signup and view all the answers

    How do ionic bonds contribute to protein structure?

    <p>By aiding in protein folding and maintaining shape.</p> Signup and view all the answers

    How do amino acids link together to form proteins?

    <p>Via peptide bonds between carboxylic and amino groups</p> Signup and view all the answers

    What is the impact of disruption in lipid levels in the body?

    <p>Can be related to diseases like obesity and diabetes</p> Signup and view all the answers

    Which statement is true regarding high energy compounds like ATP?

    <p>They serve as a universal energy currency in cells.</p> Signup and view all the answers

    Which of the following statements about amino acids is false?

    <p>Amino acids can be classified solely by their side chains</p> Signup and view all the answers

    What is a key characteristic of hydrogen bonds compared to covalent bonds?

    <p>They are electrostatic attractions and weaker.</p> Signup and view all the answers

    What function does collagen primarily serve in the body?

    <p>It provides structural support in tissues</p> Signup and view all the answers

    Which of these compounds is NOT classified as a high energy compound?

    <p>Sodium chloride</p> Signup and view all the answers

    In what form are ionic compounds typically found in the body?

    <p>Dry salts</p> Signup and view all the answers

    Which of the following is a role of proteins beyond structural support?

    <p>Function as catalysts and enzymes in biochemical reactions</p> Signup and view all the answers

    Which component is critical for the formation of elements essential for life in the body?

    <p>Proteins providing necessary amino acids</p> Signup and view all the answers

    What characterizes the amino group of an amino acid?

    <p>It contains nitrogen and hydrogen atoms</p> Signup and view all the answers

    What is the primary effect of enzyme specificity on biochemical reactions?

    <p>Each enzyme is limited to only one substrate and reaction type.</p> Signup and view all the answers

    How does the induced fit model explain enzyme function?

    <p>It describes a change in the enzyme's shape upon substrate interaction, improving fit.</p> Signup and view all the answers

    Which factors contribute to the regulation of enzyme activity?

    <p>Regulatory molecules can increase or decrease enzyme activity based on cellular needs.</p> Signup and view all the answers

    Why is compartmentalization of enzymes important within a cell?

    <p>Compartmentalization prevents all metabolic reactions from occurring simultaneously.</p> Signup and view all the answers

    How do enzymes achieve their high efficiency in catalyzing reactions?

    <p>They lower the activation energy required for a reaction to proceed.</p> Signup and view all the answers

    What defines absolute specificity in enzymes?

    <p>An enzyme works exclusively on a single substrate to catalyze a specific reaction.</p> Signup and view all the answers

    What role do zymogens play in enzymatic activity?

    <p>They serve as inactive precursors activated when needed to prevent untimely reactions.</p> Signup and view all the answers

    Which characteristic best describes bond specificity in enzymes?

    <p>They focus on specific types of bonds, like peptide or ester bonds.</p> Signup and view all the answers

    What is the role of nonpolar R groups in proteins located within a hydrophobic environment?

    <p>They are found on the outside surface, interacting with the lipid environment.</p> Signup and view all the answers

    What impact does the replacement of polar glutamate with nonpolar valine have in sickle cell anemia?

    <p>It causes red blood cells to become sticky and sickle-shaped.</p> Signup and view all the answers

    What characterizes the isoelectric point (IEP) of an amino acid?

    <p>It is the pH at which the amino acid carries equal positive and negative charges.</p> Signup and view all the answers

    What critical role do polar side chains of amino acids play in protein structure?

    <p>They stabilize structures through hydrogen bonding.</p> Signup and view all the answers

    Which of the following properties explains why amino acids can act as both acids and bases?

    <p>The presence of both acidic and basic groups.</p> Signup and view all the answers

    How do dipolar ions (zwitterions) behave when an electric current is passed through a medium at their isoelectric point?

    <p>They precipitate in place without migrating.</p> Signup and view all the answers

    What is a significant function of the sulfhydryl group (-SH) in cysteine?

    <p>It helps form disulfide bonds that stabilize protein structures.</p> Signup and view all the answers

    What is the significance of the amphoteric property of amino acids in blood?

    <p>It allows for efficient buffering of pH changes.</p> Signup and view all the answers

    Which amino acid deficiency is primarily associated with changes in skin and hair pigmentation?

    <p>Tyrosine</p> Signup and view all the answers

    What serious condition can occur as a result of defects in the globin protein of hemoglobin?

    <p>Hemolysis</p> Signup and view all the answers

    Excessive intake of over-the-counter amino acids can lead to which serious health issue?

    <p>Kidney failure</p> Signup and view all the answers

    Deficiencies in which factor are associated with increased susceptibility to infections?

    <p>Immunoglobulins</p> Signup and view all the answers

    Which of the following compounds is derived from glutamine and plays a role in neurotransmission?

    <p>GABA</p> Signup and view all the answers

    Inborn errors of amino acid metabolism can lead to which of the following manifestations?

    <p>Mental retardation</p> Signup and view all the answers

    What role do hydroxy-containing amino acids play in the body?

    <p>Signal transduction</p> Signup and view all the answers

    What consequence can arise from defects in structural proteins like collagen?

    <p>Skeletal deformities</p> Signup and view all the answers

    How many hydrogen bonds are present between guanine and cytosine nucleotide bases in DNA?

    <p>Three</p> Signup and view all the answers

    What is the primary role of hydrogen bonding in protein structure?

    <p>Facilitating protein folding</p> Signup and view all the answers

    What describes a simple enzyme?

    <p>It consists only of protein molecules.</p> Signup and view all the answers

    What is the significance of breaking hydrogen bonds during DNA replication?

    <p>To allow access to the nucleotide sequence</p> Signup and view all the answers

    What characterizes a holoenzyme?

    <p>It contains a protein component and a non-protein component.</p> Signup and view all the answers

    Which type of interaction occurs between charged atoms and influences protein structure?

    <p>Electrostatic interactions</p> Signup and view all the answers

    Which of the following polysaccharides serves as the main storage form of carbohydrates in humans?

    <p>Glycogen</p> Signup and view all the answers

    What is the main function of enzymes in biological systems?

    <p>Lowering the activation energy of reactions</p> Signup and view all the answers

    What is the primary role of fiber in the human diet?

    <p>To aid digestion</p> Signup and view all the answers

    Which sugar derivative is formed when a hydroxyl group is replaced by an amino group?

    <p>Amino Sugar</p> Signup and view all the answers

    What negative effect has been associated with high levels of fructose consumption?

    <p>Increased hunger and sugar cravings</p> Signup and view all the answers

    Which type of polysaccharide is primarily unbranched and serves a structural role in plants?

    <p>Cellulose</p> Signup and view all the answers

    What components make up starch in the human diet?

    <p>Amylose and amylopectin</p> Signup and view all the answers

    Which carbohydrate derivative plays a significant role in detoxification and elimination of toxic compounds?

    <p>Glucuronic acid</p> Signup and view all the answers

    Which of the following foods primarily contains cellulose as a dietary fiber?

    <p>Green leafy vegetables</p> Signup and view all the answers

    Which classification of amino acids describes those that cannot be synthesized by the body and must be obtained from the diet?

    <p>Essential amino acids</p> Signup and view all the answers

    What property of nonpolar amino acids contributes to their clustering within the interior of proteins in aqueous solutions?

    <p>Hydrophobic effect</p> Signup and view all the answers

    Which group in the amino acid structure contributes to the unique chemical identity of each amino acid?

    <p>R group (side chain)</p> Signup and view all the answers

    In what way can amino acids be categorized based on their ability to gain or lose protons?

    <p>By their polarity</p> Signup and view all the answers

    Which unique chemical group is found in proline that distinguishes it from other amino acids?

    <p>Imino group (NH)</p> Signup and view all the answers

    Which type of amino acids can donate hydrogen ions and carry a negative charge at physiological pH?

    <p>Acidic amino acids</p> Signup and view all the answers

    Which classification of amino acids may need to be included in the diet during specific physiological conditions, such as growth or after surgery?

    <p>Semi-essential amino acids</p> Signup and view all the answers

    What is the main characteristic of aliphatic amino acids?

    <p>They have an open chain of carbon and hydrogen</p> Signup and view all the answers

    What is the primary characteristic of competitive inhibition?

    <p>The inhibitor competes with the substrate for the active site.</p> Signup and view all the answers

    Which statement best describes the effect of non-competitive inhibitors on enzyme kinetics?

    <p>They affect Vmax but leave Km unchanged.</p> Signup and view all the answers

    What happens to the enzyme's affinity for the substrate when a competitive inhibitor is present?

    <p>The affinity is decreased.</p> Signup and view all the answers

    In what way does increasing substrate concentration affect competitive inhibition?

    <p>It can reverse the effects of competitive inhibition.</p> Signup and view all the answers

    Which of the following is a common example of non-competitive inhibition?

    <p>Metabolic intermediates inhibiting enzyme activity.</p> Signup and view all the answers

    What is a characteristic outcome when a non-competitive inhibitor binds to an enzyme-substrate complex?

    <p>The catalytic activity of the enzyme is reduced.</p> Signup and view all the answers

    Which enzyme characteristic is affected by the presence of a non-competitive inhibitor?

    <p>Maximum reaction velocity (Vmax).</p> Signup and view all the answers

    How does the structural similarity of a competitive inhibitor to the substrate influence its action?

    <p>It allows binding to the active site, preventing substrate access.</p> Signup and view all the answers

    What is the optimal temperature for most human enzymes to achieve maximal enzyme activity?

    <p>37°C</p> Signup and view all the answers

    How does the pH level specifically influence the catalytic activity of an enzyme such as pepsin?

    <p>It is maximally active in acidic conditions at pH 1-2.</p> Signup and view all the answers

    What occurs to enzyme reaction velocity when the temperature exceeds the optimum level and leads to denaturation?

    <p>The enzyme becomes inactive and reaction velocity decreases.</p> Signup and view all the answers

    Which factor must be considered to understand the variability in enzyme activity across different enzymes?

    <p>Optimum pH varies among different enzymes based on their environment in the body.</p> Signup and view all the answers

    Which statement best describes the effect of temperature on enzyme activity within the range of 0° to 40°C?

    <p>Enzyme activity doubles with each 10°C increase.</p> Signup and view all the answers

    What is the primary reason immature babies are more prone to jaundice?

    <p>Low levels of glucuronic acid</p> Signup and view all the answers

    What condition can arise from severe jaundice in infants, related to the brain?

    <p>Kernicterus</p> Signup and view all the answers

    Which of the following sugar alcohols is primarily used as a diuretic?

    <p>Mannitol</p> Signup and view all the answers

    How do carbohydrates compare to proteins and fats in terms of energy conversion efficiency?

    <p>Carbohydrates are more readily converted into glucose</p> Signup and view all the answers

    Which disease is primarily associated with abnormal glucose metabolism?

    <p>Diabetes Mellitus</p> Signup and view all the answers

    What are the caloric implications of sorbitol as compared to normal sugars?

    <p>Contains 50% less calories than sugar</p> Signup and view all the answers

    Excessive use of which sugar alcohol can lead to bloating and digestive issues?

    <p>Sorbitol</p> Signup and view all the answers

    What role do carbohydrates play in human diets aside from providing energy?

    <p>Serve as cell membrane components for communication</p> Signup and view all the answers

    What is the consequence of a severe deficiency of glutamine in the body?

    <p>Convulsions and neurological issues</p> Signup and view all the answers

    Which amino acid is linked to the production of several key neurotransmitters and hormones, leading to color loss in skin and hair upon its deficiency?

    <p>Tyrosine</p> Signup and view all the answers

    What can excessive intake of branched-chain amino acids primarily lead to in the context of kidney health?

    <p>Kidney overload and potential failure</p> Signup and view all the answers

    Which condition is potentially exacerbated by defects in globin protein of hemoglobin?

    <p>Hemolytic anemia</p> Signup and view all the answers

    What can occur as a result of inborn errors of amino acid metabolism?

    <p>Cognitive impairment and physical disabilities</p> Signup and view all the answers

    What type of diseases can be caused by defects in structural proteins such as collagen?

    <p>Skeletal deformities and joint issues</p> Signup and view all the answers

    What is a consequence of defects in the production of hormones, specifically insulin?

    <p>Diabetes mellitus</p> Signup and view all the answers

    What is the role of hydroxy-containing amino acids in the body?

    <p>Signal transduction across cell membranes</p> Signup and view all the answers

    What serious outcome can result from a deficiency of coagulation factors?

    <p>Uncontrolled wound bleeding</p> Signup and view all the answers

    In what way can deposition of abnormal proteins affect health?

    <p>Development of neurodegenerative diseases</p> Signup and view all the answers

    What is the primary reason hydrogen bonds are crucial in DNA structure?

    <p>They hold nucleotide bases together, enabling pairs to form.</p> Signup and view all the answers

    Which statement correctly describes the role of electrostatic interactions in proteins?

    <p>They are involved in creating the three-dimensional structure of proteins.</p> Signup and view all the answers

    What differentiates a holoenzyme from a simple enzyme?

    <p>Holoenzymes can include both proteins and non-protein elements.</p> Signup and view all the answers

    What would likely happen if hydrogen bonds in DNA were not broken during replication?

    <p>The DNA strands would not separate, halting replication.</p> Signup and view all the answers

    Why are enzymes critical for metabolic reactions in living organisms?

    <p>They increase the rate of reactions without changing the reaction pathways.</p> Signup and view all the answers

    What component of a holoenzyme is termed the apoenzyme?

    <p>The protein portion that requires a coenzyme for activity.</p> Signup and view all the answers

    Which of the following statements is accurate regarding the role of energy barriers in enzymatic reactions?

    <p>They are lowered by enzyme activity, facilitating reactions.</p> Signup and view all the answers

    How do hydrogen bonds affect protein folding?

    <p>They stabilize secondary and tertiary structures through attractions.</p> Signup and view all the answers

    What consequence would arise from an absence of enzymes in cellular reactions?

    <p>Reactions would take place at rates too slow to support life.</p> Signup and view all the answers

    What role do lipids play in cellular processes?

    <p>They act as signaling molecules and aid in the transport of fat-soluble vitamins.</p> Signup and view all the answers

    Which of the following statements about proteins is incorrect?

    <p>Proteins are solely responsible for energy production in cells.</p> Signup and view all the answers

    Amino acids, the building blocks of proteins, are characterized by which functional group?

    <p>A carboxylic group (–COOH) and an amino group (–NH2)</p> Signup and view all the answers

    What is the primary cause of diseases related to lipids?

    <p>Disruption in lipid levels due to dietary intake or metabolism.</p> Signup and view all the answers

    Which type of protein is essential for the movement of muscles?

    <p>Contractile proteins</p> Signup and view all the answers

    What type of bond is formed between amino acids during protein synthesis?

    <p>Peptide bond</p> Signup and view all the answers

    Which protein is primarily responsible for oxygen transport in the bloodstream?

    <p>Hemoglobin</p> Signup and view all the answers

    Which of the following is NOT a function of proteins in the body?

    <p>Storing genetic information</p> Signup and view all the answers

    In the context of protein synthesis, what is the role of secondary messengers?

    <p>To transmit signals within and between cells.</p> Signup and view all the answers

    What are the naturally occurring amino acids used for in protein synthesis called?

    <p>Primary amino acids</p> Signup and view all the answers

    What characteristic of unsaturated fatty acids differentiates them from saturated fatty acids?

    <p>Unsaturated fatty acids contain one or more double bonds.</p> Signup and view all the answers

    How does the presence of double bonds affect the melting temperature (Tm) of fatty acids?

    <p>Double bonds decrease the melting temperature.</p> Signup and view all the answers

    What is the chain length range for medium chain fatty acids (MCFA)?

    <p>7 to 12 carbon atoms.</p> Signup and view all the answers

    What is a common source of short chain fatty acids that can be produced in the human body?

    <p>High-fiber foods.</p> Signup and view all the answers

    What configuration is characteristic of double bonds in natural fatty acids?

    <p>Cis configuration.</p> Signup and view all the answers

    What role do medium chain fatty acids (MCFA) play in diet, compared to long chain fatty acids?

    <p>MCFAs are often considered healthier due to their benefits.</p> Signup and view all the answers

    What impact do trans double bonds in fatty acids have on health outcomes?

    <p>They are linked to an increased risk of atherosclerosis.</p> Signup and view all the answers

    How are long chain length fatty acids (LCFA) transported in circulation?

    <p>In association with proteins.</p> Signup and view all the answers

    Which temperature range causes enzyme activity to double for most human enzymes?

    <p>0° to 40°C</p> Signup and view all the answers

    What term describes the temperature at which maximal enzyme activity is achieved?

    <p>Optimum temperature</p> Signup and view all the answers

    At what pH does the digestive enzyme pepsin exhibit its maximal activity?

    <p>pH 1-2</p> Signup and view all the answers

    What effect does fever have on enzyme function?

    <p>It may denature enzymes if temperature exceeds limits.</p> Signup and view all the answers

    Which factor does NOT directly affect enzyme activity?

    <p>Time of day</p> Signup and view all the answers

    Why can hypothermia affect enzyme function severely?

    <p>It inactivates enzymes by lowering temperature.</p> Signup and view all the answers

    What is indicated by the term 'optimum pH' for an enzyme?

    <p>It is the pH at which enzyme activity is maximized.</p> Signup and view all the answers

    How does an increase in pH generally affect enzyme activity?

    <p>It may deactivate enzymes depending on their pH tolerance.</p> Signup and view all the answers

    What type of fatty acids are predominantly found in the human body?

    <p>Fatty acids with an even number of carbon atoms</p> Signup and view all the answers

    Which of the following is a primary cause of rancidity in lipids?

    <p>Exposure to moisture and heat</p> Signup and view all the answers

    Which essential fatty acid is a precursor of ω-3 fatty acids?

    <p>α-linolenic acid</p> Signup and view all the answers

    What role do antioxidants play in lipid stability?

    <p>They inhibit oxidative rancidity</p> Signup and view all the answers

    What is the approximate caloric value of 1 gram of dietary lipids?

    <p>9 Cal</p> Signup and view all the answers

    What is a common sign of essential fatty acid deficiency?

    <p>Hair loss</p> Signup and view all the answers

    Which fatty acid is commonly found in walnuts and sunflower oil?

    <p>Linoleic acid</p> Signup and view all the answers

    What happens to lipids when they are exposed to bacterial action?

    <p>They undergo rancidity</p> Signup and view all the answers

    What is the role of hydrogen bonds in the structure of DNA?

    <p>They connect nucleotide bases to each other.</p> Signup and view all the answers

    What initiates DNA replication in cells?

    <p>Breaking of hydrogen bonds between nucleotide bases.</p> Signup and view all the answers

    Which statement best describes the function of enzymes in biological systems?

    <p>They act as catalysts without being consumed in the reaction.</p> Signup and view all the answers

    What distinguishes a simple enzyme from a holoenzyme?

    <p>Holoenzymes contain both protein and non-protein components.</p> Signup and view all the answers

    How do electrostatic interactions affect the structure of proteins?

    <p>They can be either repulsive or attractive, influencing protein 3D structure.</p> Signup and view all the answers

    What is a key consequence of the high energy barrier in cellular reactions without enzymes?

    <p>Most cellular reactions cannot occur spontaneously.</p> Signup and view all the answers

    What component is termed the apoenzyme in a holoenzyme?

    <p>The protein portion of the holoenzyme.</p> Signup and view all the answers

    Why are hydrogen bonds considered weaker than covalent bonds?

    <p>They result from transient electrostatic interactions.</p> Signup and view all the answers

    What term is used for an inorganic group that is a non-protein component of a holoenzyme?

    <p>Cofactor</p> Signup and view all the answers

    Which type of enzyme has different physical and chemical characteristics but similar catalytic activity?

    <p>Isoenzymes (Isozymes)</p> Signup and view all the answers

    What is the significance of the rate limiting step in an enzymatic reaction?

    <p>It dictates the overall speed of the reaction.</p> Signup and view all the answers

    How does the substrate bind to the enzyme according to the induced-fit model?

    <p>The enzyme changes shape to accommodate the substrate.</p> Signup and view all the answers

    What is formed when an enzyme binds to its substrate?

    <p>Enzyme-substrate (ES) complex</p> Signup and view all the answers

    What type of group is often referred to when it is tightly bound to an enzyme and difficult to remove?

    <p>Prosthetic group</p> Signup and view all the answers

    Which statement best describes the binding of the substrate to the enzyme?

    <p>It forms through non-covalent interactions like hydrogen bonds.</p> Signup and view all the answers

    What is the primary attribute of the active site in an enzyme?

    <p>It has a specific shape complementary to the substrate.</p> Signup and view all the answers

    What defines the R group in amino acids?

    <p>It is a side chain that distinguishes each amino acid.</p> Signup and view all the answers

    Which classification of amino acids can be synthesized by the body under normal conditions?

    <p>Non-essential amino acids</p> Signup and view all the answers

    What happens to nonpolar amino acids in an aqueous environment?

    <p>They cluster together in the protein's interior.</p> Signup and view all the answers

    How are amino acids classified according to their charge?

    <p>As neutral, acidic, and basic</p> Signup and view all the answers

    What is a characteristic of aromatic amino acids?

    <p>They contain a benzene ring in their structure.</p> Signup and view all the answers

    Which group of amino acids is considered hydrophilic?

    <p>Polar amino acids</p> Signup and view all the answers

    What is the significance of hydrophobic interactions in proteins?

    <p>They help proteins maintain their three-dimensional structure.</p> Signup and view all the answers

    Which of the following amino acids contains a sulfur group in its side chain?

    <p>Cysteine</p> Signup and view all the answers

    What type of lipids are formed from glycerol and fatty acids?

    <p>True Fats</p> Signup and view all the answers

    Which of the following best describes the amphipathic nature of fatty acids?

    <p>They possess both hydrophilic and hydrophobic regions.</p> Signup and view all the answers

    Which of the following lipids contains carbohydrate residues?

    <p>Glycolipids</p> Signup and view all the answers

    What characterizes the reaction rate when substrate concentration is much lower than Km?

    <p>The rate is directly proportional to substrate concentration.</p> Signup and view all the answers

    What is the primary health consequence associated with excessive carbohydrate intake?

    <p>Heart diseases</p> Signup and view all the answers

    What type of lipids are classified as derived lipids?

    <p>Fatty acids</p> Signup and view all the answers

    What is the impact on enzyme activity as product concentration increases?

    <p>Enzyme activity decreases due to potential competition with substrate.</p> Signup and view all the answers

    What distinguishes complex lipids from simple lipids?

    <p>They include additional head groups beyond fatty acids and alcohols.</p> Signup and view all the answers

    What happens to the rate of enzyme reaction when all active sites are occupied?

    <p>The reaction rate plateaus and reaches Vmax.</p> Signup and view all the answers

    What distinguishes Zymogens from active enzymes?

    <p>Zymogens are secreted in an inactive form and require activation.</p> Signup and view all the answers

    Which of the following components are commonly found in lipids?

    <p>C, H, and O primarily, with some having P, N, and S</p> Signup and view all the answers

    Which factor does NOT affect enzyme activity when substrate concentration is unlimited?

    <p>Substrate specificity</p> Signup and view all the answers

    Which category of lipids includes the hydrolytic products of other lipids?

    <p>Derived lipids</p> Signup and view all the answers

    How can enzyme activity be specifically regulated in the body?

    <p>Through zymogen activation or allosteric regulation.</p> Signup and view all the answers

    What occurs when all enzyme sites are occupied at high substrate concentrations?

    <p>The reaction rate reaches a constant maximum value (Vmax).</p> Signup and view all the answers

    In which scenario is the enzyme activity said to be zero-order?

    <p>When there is a plateau in reaction velocity at high substrate concentrations.</p> Signup and view all the answers

    What is the term for a non-protein component that is tightly bound to an apoenzyme?

    <p>Prosthetic group</p> Signup and view all the answers

    Which of the following best describes isoenzymes?

    <p>They have different physical and chemical characteristics.</p> Signup and view all the answers

    What occurs at the rate limiting step in an enzymatic reaction?

    <p>It determines the pace for the entire reaction.</p> Signup and view all the answers

    What model describes the binding of substrate to enzyme more accurately than the key lock model?

    <p>Induced-fit model</p> Signup and view all the answers

    Which of the following ions can act as a cofactor for enzymes?

    <p>Fe2+</p> Signup and view all the answers

    What happens when the substrate binds to the active site of an enzyme?

    <p>The enzyme changes shape to accommodate the substrate.</p> Signup and view all the answers

    How does the presence of multiple isoenzymes benefit the body?

    <p>It provides different properties under varying physiological conditions.</p> Signup and view all the answers

    What type of interactions are primarily involved in the formation of the enzyme-substrate complex?

    <p>Hydrogen bonds and hydrophobic interactions</p> Signup and view all the answers

    What is the primary effect of irreversible inhibition on an enzyme?

    <p>It permanently inactivates the enzyme regardless of substrate concentration.</p> Signup and view all the answers

    Which of the following statements is true regarding the role of reducing agents like vitamin C and E?

    <p>They help restore enzyme activity that is inhibited by certain toxins.</p> Signup and view all the answers

    What is a characteristic feature of non-functional plasma enzymes?

    <p>Their levels in plasma remain relatively constant under healthy conditions.</p> Signup and view all the answers

    What is a clinical consequence of lead exposure related to enzyme function?

    <p>Development of anemia due to enzyme inhibition.</p> Signup and view all the answers

    Which of the following scenarios would most likely demonstrate irreversible enzyme inhibition?

    <p>Cyanide interacting with enzymes responsible for ATP synthesis.</p> Signup and view all the answers

    How does irreversible inhibition affect the Vmax and Km of an enzyme?

    <p>Vmax decreases whereas Km stays the same.</p> Signup and view all the answers

    What impact do organophosphates have on enzyme activity?

    <p>Irreversible inhibition of enzymes controlling nerve signals.</p> Signup and view all the answers

    What can happen to plasma enzyme levels when there is significant tissue damage?

    <p>Elevated enzyme levels correlating with the extent of tissue damage.</p> Signup and view all the answers

    What structural characteristic differentiates triacylglycerols from monoacylglycerols?

    <p>Triacylglycerols contain three fatty acids, while monoacylglycerols contain one.</p> Signup and view all the answers

    Which of the following statements about complex lipids is most accurate?

    <p>They always include a hydrophilic head group.</p> Signup and view all the answers

    What distinguishes amino acids chemically from one another?

    <p>The R group or side chain</p> Signup and view all the answers

    Which property of fatty acids contributes to their amphipathic nature?

    <p>The ionic nature of the terminal carboxyl group.</p> Signup and view all the answers

    Which classification of amino acids includes methionine and cysteine?

    <p>Amino acids with sulfur groups</p> Signup and view all the answers

    In which condition are amino acids classified as semi-essential?

    <p>During periods of increased physiological demand</p> Signup and view all the answers

    What component is NOT typically classified as a derived lipid?

    <p>Triglycerides</p> Signup and view all the answers

    Which type of lipid is most involved in forming cellular membranes?

    <p>Phospholipids</p> Signup and view all the answers

    What is the term for the phenomenon where nonpolar amino acids cluster together in a polar environment?

    <p>Hydrophobic effect</p> Signup and view all the answers

    Which property do nonpolar amino acids exhibit in a protein's structure?

    <p>They remain in the protein's interior away from water.</p> Signup and view all the answers

    How does excessive carbohydrate intake primarily affect health?

    <p>It is associated with obesity and heart diseases.</p> Signup and view all the answers

    According to charge classification, which type of amino acid can accept protons and carry a positive charge?

    <p>Basic amino acids</p> Signup and view all the answers

    Which characteristic is indicative of simple lipids?

    <p>Esters formed only with glycerol.</p> Signup and view all the answers

    What can result from an imbalance in lipid metabolism?

    <p>Potential development of chronic diseases.</p> Signup and view all the answers

    Which of the following classifications includes amino acids that cannot be synthesized in the body?

    <p>Essential amino acids</p> Signup and view all the answers

    Which characteristic of amino acids is based on their ability to participate in hydrogen or ionic bonds?

    <p>Classification by polarity</p> Signup and view all the answers

    What is the impact of replacing polar glutamate with nonpolar valine in hemoglobin A?

    <p>RBCs becoming sticky and potential blockage of blood vessels</p> Signup and view all the answers

    The amphoteric property of amino acids allows them to behave as what in solution?

    <p>Both acids and bases</p> Signup and view all the answers

    How do polar side groups in amino acids contribute to protein structure stability?

    <p>By participating in hydrogen bond formation</p> Signup and view all the answers

    What does the isoelectric point (IEP) of an amino acid signify?

    <p>The pH at which it carries equal positive and negative charges</p> Signup and view all the answers

    What role does the side chain of cysteine serve in protein functionality?

    <p>Formation of disulfide bonds that stabilize protein structure</p> Signup and view all the answers

    Why is the amphoteric property of amino acids advantageous for plasma proteins?

    <p>It enables effective buffering systems to maintain blood pH</p> Signup and view all the answers

    What is a characteristic consequence of amino acids being zwitterions at their isoelectric point?

    <p>They exhibit no net charge</p> Signup and view all the answers

    In what manner does the hydrophobic environment affect the positioning of nonpolar R groups in proteins?

    <p>They are found on the outside surface interacting with lipids</p> Signup and view all the answers

    What role do lipids play in the transport of fat-soluble vitamins?

    <p>Lipids facilitate the solubilization and transportation of fat-soluble vitamins.</p> Signup and view all the answers

    Which of the following correctly describes the structure of an amino acid?

    <p>An amino acid consists of a carboxylic group, an amino group, and a hydrogen atom attached to an alpha-carbon.</p> Signup and view all the answers

    What function do proteins serve in regulating metabolism?

    <p>Proteins act as enzymes and hormones to direct and regulate metabolic processes.</p> Signup and view all the answers

    How are proteins formed from amino acids?

    <p>Proteins are synthesized when amino acids are linked by peptide bonds between their carboxylic and amino groups.</p> Signup and view all the answers

    What is the consequence of disrupted lipid levels in the body?

    <p>It can contribute to diseases like obesity, diabetes, and abnormalities in fat-soluble vitamins.</p> Signup and view all the answers

    What distinguishes the structure of collagen in the body?

    <p>Collagen is a structural protein that forms a framework for calcium phosphate crystals in bones.</p> Signup and view all the answers

    Which proteins are responsible for transporting essential molecules in the bloodstream?

    <p>Hemoglobin and albumin.</p> Signup and view all the answers

    What is the primary function of zymogens in the body?

    <p>To prevent auto-digestion of tissues producing digestive enzymes</p> Signup and view all the answers

    What function do secondary messengers have in cellular communication?

    <p>They transmit signals between and inside cells.</p> Signup and view all the answers

    What is the effect of phosphorylation on enzyme activity?

    <p>It can activate or deactivate enzymes depending on the specific enzyme</p> Signup and view all the answers

    Which of the following accurately describes allosteric effectors?

    <p>They influence enzyme activity by binding at sites other than the active site</p> Signup and view all the answers

    What principle governs feedback inhibition in enzymatic reactions?

    <p>The final product reduces the rate of a previous enzyme in the pathway</p> Signup and view all the answers

    How does enzyme synthesis contribute to enzyme regulation?

    <p>It alters the total number of enzyme active sites over a longer timeframe</p> Signup and view all the answers

    In enzymatic reactions, what is meant by a 'Committed-Step Enzyme'?

    <p>It is the first enzyme to act but not necessarily the one that controls the pathway's rate</p> Signup and view all the answers

    What distinguishes allosteric enzymes from regular enzymes?

    <p>They can be regulated by effectors binding to allosteric sites</p> Signup and view all the answers

    What characterizes the process of covalent modification in enzymes?

    <p>It may involve the addition of phosphate groups to alter enzyme activity</p> Signup and view all the answers

    Which of the following carbohydrates is composed of two glucose molecules?

    <p>Maltose</p> Signup and view all the answers

    What type of carbohydrate is characterized by having 2-10 monosaccharide units?

    <p>Oligosaccharides</p> Signup and view all the answers

    Which of the following is a characteristic of monosaccharides?

    <p>They contain a carbonyl group.</p> Signup and view all the answers

    What is the primary component of lactose?

    <p>Glucose and galactose</p> Signup and view all the answers

    Why is lactose considered significant for infants?

    <p>It aids in the absorption of calcium, copper, and zinc.</p> Signup and view all the answers

    Which of the following statements about isomers is true?

    <p>Isomers have the same chemical formula but different structures.</p> Signup and view all the answers

    What defines a polysaccharide?

    <p>A sugar containing more than 10 monosaccharide units.</p> Signup and view all the answers

    Which of the following physiological roles is associated with carbohydrates?

    <p>They provide energy and help in metabolic processes.</p> Signup and view all the answers

    What is the effect of cis double bonds on the structure of fatty acids?

    <p>They cause the fatty acid to bend or kink.</p> Signup and view all the answers

    Which type of fatty acids are primarily associated with an increased risk of atherosclerosis?

    <p>Trans fatty acids</p> Signup and view all the answers

    How does the addition of double bonds affect the melting temperature of fatty acids?

    <p>It decreases the melting temperature.</p> Signup and view all the answers

    What is a characteristic of medium chain fatty acids (MCFA)?

    <p>They contribute to gut health without harming beneficial bacteria.</p> Signup and view all the answers

    What defines the chain length of long chain fatty acids (LCFA)?

    <p>13 or more carbon atoms</p> Signup and view all the answers

    Which food items are typically rich in cis double bonds?

    <p>Salmon, nuts, and olive oil</p> Signup and view all the answers

    What is one of the functions of lipids in the human body?

    <p>Transport of fat-soluble vitamins</p> Signup and view all the answers

    Which of the following describes the structure of an amino acid?

    <p>Has a carboxylic group and an amino group</p> Signup and view all the answers

    What effect do saturated and trans fatty acids have on human health?

    <p>They are associated with an increased risk of atherosclerosis.</p> Signup and view all the answers

    How do proteins contribute to immunity?

    <p>By fighting infectious bacteria and viruses</p> Signup and view all the answers

    Why are medium chain fatty acids (MCFA) considered a healthy dietary component?

    <p>They provide higher satiety and reduce appetite.</p> Signup and view all the answers

    What bond is formed between amino acids during protein synthesis?

    <p>Peptide bond</p> Signup and view all the answers

    Which of the following statements about proteins is false?

    <p>Proteins are the least diverse molecules in living organisms</p> Signup and view all the answers

    Which condition is related to the disruption of lipid levels in the body?

    <p>Obesity</p> Signup and view all the answers

    What is the primary function of collagen in the body?

    <p>Providing structural support</p> Signup and view all the answers

    Which protein plays a role in oxygen transport in the bloodstream?

    <p>Hemoglobin</p> Signup and view all the answers

    What is the enzymatic reaction order when the substrate concentration is much less than Km?

    <p>First order</p> Signup and view all the answers

    What occurs when substrate concentration is much greater than Km?

    <p>All enzyme active sites are occupied</p> Signup and view all the answers

    Which factor does not impact the rate of enzymatic reactions when enzyme concentration is increased?

    <p>Saturation of enzyme active sites</p> Signup and view all the answers

    How do products affect enzyme activity during a reaction?

    <p>They decrease activity due to changes in pH or binding at allosteric sites</p> Signup and view all the answers

    What best describes zymogens?

    <p>Proenzymes activated by peptide bond hydrolysis</p> Signup and view all the answers

    Which variant of the enzyme is known to have a high Km for glucose in the liver?

    <p>Glucokinase</p> Signup and view all the answers

    What is primarily affected when enzyme concentration is limited and substrate concentration is unlimited?

    <p>Rate of reaction reaches a maximum Vmax</p> Signup and view all the answers

    What is a potential outcome of product accumulation during an enzymatic reaction?

    <p>Decreased enzyme activity</p> Signup and view all the answers

    What is the primary role of zymogens in the body?

    <p>To prevent auto-digestion of tissue</p> Signup and view all the answers

    Which statement best describes the process of covalent modification in enzyme regulation?

    <p>Enzymes can be modified reversibly by phosphate group addition</p> Signup and view all the answers

    How do allosteric enzymes differ from traditional enzymes?

    <p>They can bind to effectors at allosteric sites</p> Signup and view all the answers

    What triggers feedback inhibition in enzyme regulation?

    <p>End products binding to the committed-step enzyme</p> Signup and view all the answers

    What is the primary mechanism by which enzyme synthesis is regulated?

    <p>Alteration in the rate of transcription</p> Signup and view all the answers

    Why are positive and negative effectors important for allosteric enzymes?

    <p>They alter the catalytic activity of the enzyme</p> Signup and view all the answers

    What differentiates induction from repression in enzyme synthesis regulation?

    <p>Induction results in increased enzyme activity, while repression decreases it</p> Signup and view all the answers

    What is the general time frame for changes in enzyme activity due to allosteric or covalent modification?

    <p>Seconds to minutes</p> Signup and view all the answers

    What is the primary reason diabetics and obese patients may use sucrose derivatives instead of glucose?

    <p>They have a sweeter taste with lower concentration.</p> Signup and view all the answers

    Which polysaccharide is primarily used as a storage form in humans?

    <p>Glycogen</p> Signup and view all the answers

    What type of fiber is derived from cellulose and cannot be digested by humans?

    <p>Insoluble fiber</p> Signup and view all the answers

    What modification occurs in deoxy-monosaccharides that distinguishes them from regular monosaccharides?

    <p>The –OH group is replaced with a hydrogen atom.</p> Signup and view all the answers

    What is a significant role of glucuronic acid in the body?

    <p>Detoxification process</p> Signup and view all the answers

    Which type of bond results from the transfer of electrons between atoms?

    <p>Ionic bond</p> Signup and view all the answers

    Which molecule is not a component of plant storage polysaccharides?

    <p>Chitin</p> Signup and view all the answers

    What is the primary function of high energy bonds in ATP?

    <p>Driving metabolic processes</p> Signup and view all the answers

    Which of the following is NOT classified as a high energy compound?

    <p>Glucose</p> Signup and view all the answers

    Which of the following polysaccharides can be used as a plasma volume expander in medical treatments?

    <p>Dextrins</p> Signup and view all the answers

    Which sugar derivative has an –NH2 group replacing an –OH group?

    <p>Amino sugars</p> Signup and view all the answers

    What characterizes the bonds involved in protein tertiary and quaternary structures?

    <p>Ionic bonds and hydrogen bonds</p> Signup and view all the answers

    Which statement accurately describes hydrogen bonds?

    <p>They involve the attraction of a hydrogen atom to a lone pair of electrons.</p> Signup and view all the answers

    Which type of rancidity is primarily caused by the exposure of lipids to oxygen?

    <p>Oxidative rancidity</p> Signup and view all the answers

    Which of the following high energy compounds directly participates in energy transfer in metabolic processes?

    <p>GTP</p> Signup and view all the answers

    Which fatty acids are considered essential and must be obtained through diet?

    <p>Linoleic acid and α-linolenic acid</p> Signup and view all the answers

    What is the primary energy yield from 1 gram of dietary lipids?

    <p>9 Cal</p> Signup and view all the answers

    What is a significant property of non-covalent bonds?

    <p>They are typically weaker and reversible.</p> Signup and view all the answers

    During protein folding, which type of bond primarily aids in stabilizing the final structure?

    <p>Ionic bond</p> Signup and view all the answers

    Which of the following statements accurately describes long chain fatty acids?

    <p>They mostly consist of more than 12 carbon atoms.</p> Signup and view all the answers

    What could be a consequence of a deficiency in essential fatty acids in an infant's diet?

    <p>Hair loss and intellectual disability</p> Signup and view all the answers

    Which type of bond is typically found in dry forms such as salts?

    <p>Ionic bonds</p> Signup and view all the answers

    What is the role of sulfhydryl groups in protein structure?

    <p>Establishing disulfide bonds</p> Signup and view all the answers

    How can rancidity in fats be effectively inhibited?

    <p>By adding antioxidants and storing in cool, dark places</p> Signup and view all the answers

    Which fatty acids predominantly occur in the human body?

    <p>Fatty acids with an even number of carbon atoms</p> Signup and view all the answers

    Which of the following foods is a rich source of ω-3 fatty acids?

    <p>Flaxseeds</p> Signup and view all the answers

    What is the primary function of essential fatty acids in the body?

    <p>To support growth and development processes</p> Signup and view all the answers

    Which of the following compounds are formed as a result of oxidative rancidity?

    <p>Peroxides, aldehydes, and ketones</p> Signup and view all the answers

    What is the mechanism by which lead affects enzymes in the heme synthesis pathway?

    <p>Irreversible inhibition by forming covalent bonds with enzymes</p> Signup and view all the answers

    Which of the following best explains the clinical implication of organophosphates?

    <p>They cause irreversible inhibition of enzymes that regulate nerve signals.</p> Signup and view all the answers

    What role do reducing agents like vitamin C and vitamin E play in the context of lead exposure?

    <p>They restore the function of enzymes inhibited by lead.</p> Signup and view all the answers

    How does irreversible inhibition differ from competitive inhibition in terms of enzyme kinetics?

    <p>Irreversible inhibition does not affect Km but decreases Vmax.</p> Signup and view all the answers

    What clinical significance do non-functional plasma enzymes have in diagnosing diseases?

    <p>Their elevation in plasma indicates tissue damage correlating with disease severity.</p> Signup and view all the answers

    What term is used for the non-protein component that binds tightly to an apoenzyme and is difficult to remove?

    <p>Prosthetic group</p> Signup and view all the answers

    What defines an isoenzyme?

    <p>Enzymes that catalyze the same reaction but differ in physical and chemical properties</p> Signup and view all the answers

    Which type of interaction is primarily involved when a substrate binds to an enzyme's active site?

    <p>Hydrogen bonds and hydrophobic interactions</p> Signup and view all the answers

    How is the rate limiting step in an enzymatic reaction characterized?

    <p>It determines the overall rate of the reaction</p> Signup and view all the answers

    Which form of lactate dehydrogenase is associated with muscle tissue?

    <p>LDH-5</p> Signup and view all the answers

    What feature distinguishes the induced-fit model of enzyme-substrate binding?

    <p>The binding site adjusts to accommodate the substrate</p> Signup and view all the answers

    Which of the following ions is considered an inorganic cofactor?

    <p>Zn 2+</p> Signup and view all the answers

    During what stage does the substrate convert to an enzyme-product complex?

    <p>During the formation of the ES complex</p> Signup and view all the answers

    Which property of enzymes enables them to increase the rate of biochemical reactions?

    <p>They lower the activation energy required</p> Signup and view all the answers

    What aspect of the enzyme dictates its specific substrate binding?

    <p>Shape and charge of the active site</p> Signup and view all the answers

    Which carbohydrate consists of two monosaccharide units?

    <p>Maltose</p> Signup and view all the answers

    What is the primary health concern associated with lactose?

    <p>Many people experience lactose intolerance.</p> Signup and view all the answers

    Which type of carbohydrate is composed of more than ten monosaccharide units?

    <p>Polysaccharides</p> Signup and view all the answers

    Which of the following is NOT a characteristic of monosaccharides?

    <p>Always consist of six carbon atoms.</p> Signup and view all the answers

    In which food products is lactose primarily found?

    <p>Milk and dairy products</p> Signup and view all the answers

    Which disaccharide is known as cane sugar?

    <p>Sucrose</p> Signup and view all the answers

    What role does galactose play in health?

    <p>It helps with calcium absorption.</p> Signup and view all the answers

    What type of sugar is derived from starch degradation?

    <p>Maltose</p> Signup and view all the answers

    What is the primary mechanism by which lead causes anemia?

    <p>It non-competitively inhibits important enzymes in the heme synthesis pathway.</p> Signup and view all the answers

    How do reducing agents like vitamin C and vitamin E affect enzyme activity in individuals exposed to high pollution?

    <p>They restore the activity of inhibited enzymes.</p> Signup and view all the answers

    What is a characteristic of irreversible enzyme inhibition by organophosphates?

    <p>It involves covalent bonding to enzyme functional groups.</p> Signup and view all the answers

    What is the primary consequence of elevated levels of non-functional plasma enzymes in the context of disease?

    <p>They correlate with the extent of tissue damage.</p> Signup and view all the answers

    What is the effect of cyanide on enzymatic activity, and why is it clinically significant?

    <p>It leads to irreversible inhibition of ATP-synthesizing enzymes.</p> Signup and view all the answers

    What structural feature differentiates saturated fatty acids from unsaturated fatty acids?

    <p>Higher melting temperature due to absence of double bonds</p> Signup and view all the answers

    What is the effect of introducing a cis double bond into a fatty acid chain?

    <p>Causes a kink or bend in the fatty acid structure</p> Signup and view all the answers

    Which type of fatty acid is primarily represented in coconut oil?

    <p>Medium chain fatty acids</p> Signup and view all the answers

    How does the presence of double bonds in fatty acids impact membrane fluidity?

    <p>Increases membrane fluidity by preventing tight packing of fatty acids</p> Signup and view all the answers

    What is a common physiological outcome of increased consumption of trans fatty acids?

    <p>Increased risk of atherosclerosis</p> Signup and view all the answers

    What is the role of high-fiber foods in relation to short chain fatty acids?

    <p>They encourage the production of short-chain fatty acids</p> Signup and view all the answers

    Which statement accurately describes the impact of a higher fatty acid chain length on melting temperature?

    <p>Higher chain length leads to increased melting temperature</p> Signup and view all the answers

    What describes the configuration of double bonds in natural fatty acids?

    <p>Cis configuration is predominant</p> Signup and view all the answers

    Which characteristic is true for medium chain fatty acids compared to long chain fatty acids?

    <p>They improve gut health by targeting harmful bacteria</p> Signup and view all the answers

    What type of double bonds are prevalent in artificially produced foods?

    <p>Trans double bonds</p> Signup and view all the answers

    How do zymogens function in terms of enzyme regulation and protection?

    <p>They prevent premature activation of enzymes to avoid tissue damage.</p> Signup and view all the answers

    Which statement about covalent modification of enzymes is true?

    <p>Phosphorylation can both activate and deactivate enzymes depending on the context.</p> Signup and view all the answers

    What is the role of allosteric effectors in regulating enzyme activity?

    <p>They alter the enzyme's structure by binding to allosteric sites, affecting activity.</p> Signup and view all the answers

    What distinguishes feedback inhibition in enzyme regulation?

    <p>It uses the end product of a metabolic pathway to inhibit an early enzyme.</p> Signup and view all the answers

    How does enzyme synthesis differ from other forms of enzyme regulation?

    <p>It alters the number of active sites through induction or repression.</p> Signup and view all the answers

    What characterizes the 'Committed-Step Enzyme' in a metabolic pathway?

    <p>It is the first irreversible enzyme unique to that specific pathway.</p> Signup and view all the answers

    What is a key difference between allosteric regulation and covalent modification of enzymes?

    <p>Allosteric regulation is reversible and generally faster than covalent modification.</p> Signup and view all the answers

    In terms of enzyme regulation, what does induction refer to?

    <p>The increase in enzyme synthesis in response to specific signals.</p> Signup and view all the answers

    What impact do positive effectors have on allosteric enzymes?

    <p>They bind to allosteric sites and enhance the catalytic activity.</p> Signup and view all the answers

    What condition can occur in immature babies due to low levels of glucuronic acid?

    <p>Jaundice and mental retardation</p> Signup and view all the answers

    Which of the following sugars is commonly used as a diuretic?

    <p>Sorbitol</p> Signup and view all the answers

    How many calories does 1 gram of dietary carbohydrates provide?

    <p>4 Cal</p> Signup and view all the answers

    What may result from abnormal glucose metabolism?

    <p>Diabetes Mellitus</p> Signup and view all the answers

    Why are carbohydrates not considered essential nutrients?

    <p>Proteins and fats can meet daily energy needs</p> Signup and view all the answers

    Which consequence can result from excessive use of sorbitol?

    <p>Bloating and digestion problems</p> Signup and view all the answers

    What is a potential effect of inborn errors in carbohydrate metabolism?

    <p>Mental retardation and hepatomegaly</p> Signup and view all the answers

    What role do carbohydrates serve in intercellular communication?

    <p>Mediate some forms of communication</p> Signup and view all the answers

    Which artificial sweetener is associated with a lower calorie count than regular sugars?

    <p>Sorbitol</p> Signup and view all the answers

    What is the primary way that carbohydrates affect human diseases?

    <p>By influencing physiological and metabolic processes</p> Signup and view all the answers

    Which polysaccharide is primarily used for energy storage in animals?

    <p>Glycogen</p> Signup and view all the answers

    What is the structural difference between amylose and amylopectin?

    <p>Amylose is unbranched, while amylopectin is branched.</p> Signup and view all the answers

    Which carbohydrate derivative specifically replaces a hydroxyl group with an amino group?

    <p>Amino sugars</p> Signup and view all the answers

    What is the primary role of glucuronic acid in the body?

    <p>Detoxification</p> Signup and view all the answers

    Which of the following polysaccharides is not digestible by humans?

    <p>Cellulose</p> Signup and view all the answers

    What makes dextrins suitable for intravenous infusion?

    <p>Their branched structure that retains plasma</p> Signup and view all the answers

    Which carbohydrate is mainly found in plant structures and is critical for maintaining plant rigidity?

    <p>Cellulose</p> Signup and view all the answers

    What effect does high levels of fructose have on appetite according to recent findings?

    <p>It increases hunger and cravings for sugar.</p> Signup and view all the answers

    Which enzyme inhibition type results in irreversible loss of enzyme activity and permanently alters enzyme function?

    <p>Irreversible inhibition</p> Signup and view all the answers

    What role do vitamin C and vitamin E play in enzyme activity concerning lead exposure?

    <p>They restore the activity of inhibited enzymes.</p> Signup and view all the answers

    What effect does irreversible inhibition have on the Vmax and Km of an enzyme?

    <p>Vmax decreases; Km remains unchanged</p> Signup and view all the answers

    In the context of plasma enzymes, what distinguishes functional plasma enzymes from non-functional plasma enzymes?

    <p>Functional enzymes are secreted into the plasma and perform specific functions.</p> Signup and view all the answers

    What clinical implication is associated with the irreversible inhibition of enzymes by organophosphates?

    <p>Interference with nerve signal control</p> Signup and view all the answers

    Which of the following amino acids contains a sulfur group in its side chain?

    <p>Methionine</p> Signup and view all the answers

    What classification would proline fall under based on its structure?

    <p>Aliphatic</p> Signup and view all the answers

    Which group can amino acids classified as basic accept in physiological pH?

    <p>Hydrogen ions</p> Signup and view all the answers

    What is one consequence of the hydrophobic effect in proteins?

    <p>Formation of a stable three-dimensional shape</p> Signup and view all the answers

    Which classification applies to histidine and arginine in relation to dietary needs?

    <p>Semi-essential</p> Signup and view all the answers

    Which type of amino acid has a side chain that is typically non-polar?

    <p>Hydrophobic amino acids</p> Signup and view all the answers

    Which statement correctly describes the role of the α-carboxyl group in amino acids?

    <p>It allows the amino acid to act as an acid.</p> Signup and view all the answers

    What is the primary reason atoms form chemical bonds?

    <p>To reach a more stable, lower-energy state</p> Signup and view all the answers

    What distinguishes aromatic amino acids from aliphatic amino acids?

    <p>Presence of a benzene ring</p> Signup and view all the answers

    Which of the following describes polar covalent bonds?

    <p>Electrons favor the more electronegative atom in the bond</p> Signup and view all the answers

    What characteristic distinguishes nonpolar covalent bonds?

    <p>Electrons are shared equally or nearly equally</p> Signup and view all the answers

    What characterizes neutral amino acids in terms of electric charge?

    <p>They carry no charge at physiological pH.</p> Signup and view all the answers

    In covalent bond classification, how does the strength of covalent bonds compare to non-covalent bonds?

    <p>Covalent bonds are stronger than non-covalent bonds</p> Signup and view all the answers

    How does the R group of an amino acid primarily influence its properties?

    <p>By distinguishing its chemical behavior</p> Signup and view all the answers

    What type of bond is created when a carbohydrate molecule joins with another molecule?

    <p>Glycosidic bond</p> Signup and view all the answers

    What happens to the electrons in a polar covalent bond between hydrogen and oxygen in water?

    <p>Electrons are predominantly closer to oxygen</p> Signup and view all the answers

    Which statement accurately describes covalent bonds?

    <p>They involve the sharing of electrons between atoms</p> Signup and view all the answers

    What is a common characteristic of non-covalent bonds?

    <p>They include hydrogen bonding and ionic interactions</p> Signup and view all the answers

    Which type of covalent bond is characterized by the sharing of more than one pair of electrons between two atoms?

    <p>Double or triple covalent bond</p> Signup and view all the answers

    What defines the stability of an atom's valence shell?

    <p>A full valence shell typically has eight electrons</p> Signup and view all the answers

    What is the role of hydrogen bonds in DNA?

    <p>They form between nucleotide bases adenine-thymine and guanine-cytosine.</p> Signup and view all the answers

    What is a key characteristic of a holoenzyme?

    <p>It includes both protein and non-protein components.</p> Signup and view all the answers

    Why are enzymes crucial for cellular reactions?

    <p>They enhance the rate of reactions by lowering the energy barrier.</p> Signup and view all the answers

    What types of interactions occur in protein folding aside from hydrogen bonds?

    <p>Electrostatic interactions.</p> Signup and view all the answers

    What happens to hydrogen bonds before DNA replication?

    <p>They must break to allow strand separation.</p> Signup and view all the answers

    What defines the nature of simple enzymes?

    <p>They are solely made up of protein molecules.</p> Signup and view all the answers

    What aspect of a charged atom influences electrostatic interactions?

    <p>The extent of its electric charge.</p> Signup and view all the answers

    What is a consequence of enzyme catalysis in biological systems?

    <p>They allow reactions to proceed at physiological conditions.</p> Signup and view all the answers

    Which factor contributes to the biomedical importance of hydrogen bonds?

    <p>They influence the structure and properties of DNA.</p> Signup and view all the answers

    How do hydrogen bonds differ from ionic bonds?

    <p>Hydrogen bonds involve polar covalent interactions.</p> Signup and view all the answers

    What can lead to kernicterus in immature babies?

    <p>Reduced levels of glucuronic acid</p> Signup and view all the answers

    How do sorbitol's effects compare to dietary sugars?

    <p>It can cause bloating with excessive use</p> Signup and view all the answers

    Which statement about carbohydrates is correct?

    <p>They can be fully converted to glucose upon digestion.</p> Signup and view all the answers

    What serious diseases might be linked to abnormal glucose metabolism?

    <p>Diabetes Mellitus and certain cancers</p> Signup and view all the answers

    What is not a primary role of carbohydrates in the body?

    <p>Producing essential amino acids</p> Signup and view all the answers

    What is a consequence of liver failure related to glucuronic acid?

    <p>Decreased glucuronic acid synthesis</p> Signup and view all the answers

    What is a characteristic effect of carbohydrates in relation to satiety?

    <p>Induce early but short-term satiety</p> Signup and view all the answers

    Which of the following can result from inborn errors in carbohydrate metabolism?

    <p>Mental retardation and hepatomegaly</p> Signup and view all the answers

    What type of bond is primarily responsible for holding the tertiary and quaternary structures of proteins together?

    <p>Ionic bonds</p> Signup and view all the answers

    Which of the following compounds is classified as a high energy compound?

    <p>ATP</p> Signup and view all the answers

    In what form are ionic bonds commonly found within the human body?

    <p>Salts</p> Signup and view all the answers

    Which of the following statements about hydrogen bonds is true?

    <p>Hydrogen bonds require a hydrogen atom to be bonded to an electronegative atom.</p> Signup and view all the answers

    What is the nature of the bonds that are classified as 'high energy bonds'?

    <p>They are easily broken and release a significant amount of energy.</p> Signup and view all the answers

    Which compounds are examples of high energy sulfur compounds?

    <p>Acetyl CoA and Succinyl CoA</p> Signup and view all the answers

    What is a consequence of non-covalent bonds being reversible?

    <p>They play a role in cellular signaling and molecular interactions.</p> Signup and view all the answers

    What specific feature characterizes phosphoric anhydride bonds in ATP?

    <p>They release energy when broken.</p> Signup and view all the answers

    Which of the following interactions is not classified as a non-covalent bond type?

    <p>Covalent bonding</p> Signup and view all the answers

    Which characteristic of ionic bonds contributes to their role in enzyme activity?

    <p>They stabilize the three-dimensional shape of enzymes.</p> Signup and view all the answers

    What role do hydrogen bonds play in the structure of DNA?

    <p>They hold nucleotide bases together between adenine-thymine and guanine-cytosine.</p> Signup and view all the answers

    When the substrate concentration is significantly lower than Km, how is the rate of the enzymatic reaction classified?

    <p>First order</p> Signup and view all the answers

    How do hydrogen bonds contribute to protein structure?

    <p>They assist in the folding of proteins into their tertiary structure.</p> Signup and view all the answers

    What occurs after an enzyme reaches a maximum rate in a reaction when the enzyme concentration continues to increase?

    <p>The reaction rate remains unchanged</p> Signup and view all the answers

    What is the nature of a holoenzyme?

    <p>It is a combination of an apoenzyme and a coenzyme.</p> Signup and view all the answers

    What happens to enzyme activity as products accumulate during a reaction?

    <p>Enzyme activity decreases due to competition</p> Signup and view all the answers

    What primarily allows enzymes to facilitate reactions in the human body?

    <p>They provide an alternative reaction pathway with a lower energy barrier.</p> Signup and view all the answers

    Which of the following statements best describes zymogens?

    <p>They are inactive forms of enzymes activated by cleavage</p> Signup and view all the answers

    What defines electrostatic interactions in biological molecules?

    <p>They can be either attractive or repulsive based on the charges of interacting atoms.</p> Signup and view all the answers

    If two variants of the same enzyme act on the same substrate but with different Km values, which statement reflects their reaction characteristics?

    <p>The variant with the higher Km has a lower affinity</p> Signup and view all the answers

    In what way do enzymes contribute to metabolic reactions?

    <p>They remain unchanged after participating in a reaction.</p> Signup and view all the answers

    What does breaking hydrogen bonds facilitate in the context of DNA?

    <p>It is required for the unwinding of the DNA double helix during replication.</p> Signup and view all the answers

    Which statement about simple enzymes is correct?

    <p>They do not require any non-protein components to function.</p> Signup and view all the answers

    Why are enzymes essential for cellular reactions?

    <p>They prevent unwanted reactions from occurring spontaneously.</p> Signup and view all the answers

    What temperature is considered the optimum for most human enzymes?

    <p>37°C</p> Signup and view all the answers

    Which factor does NOT typically lead to an increase in enzyme activity?

    <p>Excessive enzyme denaturation</p> Signup and view all the answers

    At what pH does pepsin, the digestive enzyme in the stomach, exhibit maximal activity?

    <p>pH 1-2</p> Signup and view all the answers

    What occurs to enzyme activity when temperatures exceed the optimum level?

    <p>Enzyme denaturation begins and activity decreases</p> Signup and view all the answers

    Which statement accurately characterizes the relationship between temperature and enzyme activity?

    <p>Enzyme activity varies with temperature until a peak velocity is reached</p> Signup and view all the answers

    How does a change in pH influence enzyme catalytic activity?

    <p>It affects the ionization states of the enzyme and substrate</p> Signup and view all the answers

    Which of the following conditions could be life-threatening due to its effect on enzyme function?

    <p>Hyperthermia</p> Signup and view all the answers

    What is the effect of an acidic medium on an enzyme that requires its amino group to be in a protonated form?

    <p>Enhances catalytic activity</p> Signup and view all the answers

    What is the primary factor that determines the optimum pH of an enzyme?

    <p>The specific biological function of the enzyme</p> Signup and view all the answers

    What common scenario might cause a decrease in enzymatic reaction velocity aside from substrate inhibition?

    <p>Increase in temperature beyond optimum</p> Signup and view all the answers

    Which fatty acid configuration predominates in the human body?

    <p>Fatty acids with an even number of carbon atoms</p> Signup and view all the answers

    Which type of rancidity involves hydrolysis of fat, leading to short-chain fatty acid liberation?

    <p>Hydrolytic rancidity</p> Signup and view all the answers

    Which essential fatty acid is crucial for producing ω-3 fatty acids?

    <p>α-linolenic acid</p> Signup and view all the answers

    What type of fatty acids are found in greater abundance in foods such as walnuts and sunflower oil?

    <p>ω-6 fatty acids</p> Signup and view all the answers

    What is the main consequence of essential fatty acid deficiency in infants?

    <p>Hair loss and low platelets</p> Signup and view all the answers

    Which function of lipids contributes to their role as a structural element in biological membranes?

    <p>Forming lipid bilayers</p> Signup and view all the answers

    What is the primary consequence of rancidity in fats?

    <p>Changes in taste, odour, and acidic reaction</p> Signup and view all the answers

    What is the approximate energy yield provided by 1 gram of dietary lipids?

    <p>9 Calories</p> Signup and view all the answers

    What is the primary role of hydrogen bonds in DNA structure?

    <p>They stabilize the double helix structure.</p> Signup and view all the answers

    What is the key characteristic of enzymes that distinguishes them from other proteins?

    <p>Enzymes catalyze reactions without being consumed.</p> Signup and view all the answers

    How do electrostatic interactions influence protein conformation?

    <p>By contributing to the overall 3D structure of the protein.</p> Signup and view all the answers

    Which statement best describes holoenzymes?

    <p>They require both protein and non-protein components for activity.</p> Signup and view all the answers

    What is a critical advantage of enzymatic reactions in living cells?

    <p>They lower the activation energy barriers of reactions.</p> Signup and view all the answers

    What specific process requires the breaking of hydrogen bonds in DNA?

    <p>DNA replication.</p> Signup and view all the answers

    What happens to a simple enzyme when it is exposed to extreme environmental conditions?

    <p>It is likely to denature.</p> Signup and view all the answers

    Why are enzymes essential for cellular reactions?

    <p>They allow reactions to occur at the body's pH and temperature.</p> Signup and view all the answers

    What distinguishes an apoenzyme from a holoenzyme?

    <p>An apoenzyme contains no non-protein components.</p> Signup and view all the answers

    What type of interaction occurs when oppositely charged atoms attract each other?

    <p>Electrostatic interaction.</p> Signup and view all the answers

    What mechanism describes how an enzyme changes shape to better bind a substrate?

    <p>Induced fit model</p> Signup and view all the answers

    How much faster do enzyme-catalyzed reactions typically proceed compared to uncatalyzed reactions?

    <p>10^3 to 10^8 times faster</p> Signup and view all the answers

    Which type of specificity allows certain enzymes to act only on a specific substrate?

    <p>Absolute specificity</p> Signup and view all the answers

    What is a key advantage of enzyme compartmentalization within the cell?

    <p>Isolates substrates from competition</p> Signup and view all the answers

    Which aspect of enzyme activity can be regulated to meet cellular needs?

    <p>Reaction velocity</p> Signup and view all the answers

    Which type of enzyme specificity acts on specific types of bonds?

    <p>Bond specificity</p> Signup and view all the answers

    What does a chemical enzyme predominantly do?

    <p>Accelerates chemical reactions without being consumed</p> Signup and view all the answers

    Which statement accurately describes the relationship between substrate concentration and reaction velocity when the substrate concentration is much less than Km?

    <p>The reaction rate is directly proportional to substrate concentration.</p> Signup and view all the answers

    What is a consequence of enzyme regulation in metabolic functions?

    <p>Precise control of energy storage and release</p> Signup and view all the answers

    What is the effect on enzyme activity when product concentration accumulates during a reaction?

    <p>Enzyme activity decreases due to potential allosteric inhibition.</p> Signup and view all the answers

    Which of the following is a feature of the induced fit model of enzyme action?

    <p>The enzyme undergoes a temporary conformational change upon substrate binding.</p> Signup and view all the answers

    When the substrate concentration is significantly higher than Km, which statement holds true regarding the reaction rate?

    <p>The reaction reaches a maximum velocity (Vmax) and is zero order.</p> Signup and view all the answers

    What facilitates the organization of enzymes into purposeful pathways within the cell?

    <p>Compartmentalization</p> Signup and view all the answers

    What is a characteristic of zymogens concerning enzyme activation?

    <p>They are activated through hydrolysis of specific peptide bonds.</p> Signup and view all the answers

    In the context of enzyme activity, how does increasing enzyme concentration affect the reaction when substrate is unlimited?

    <p>The reaction rate remains unchanged after reaching a certain point.</p> Signup and view all the answers

    What role do nonpolar R groups play in proteins located in hydrophobic environments?

    <p>They interact with the lipid environment on the protein's surface.</p> Signup and view all the answers

    Which amino acid side chain participates in the formation of disulfide bonds?

    <p>Cysteine</p> Signup and view all the answers

    What condition arises from the substitution of polar glutamate with nonpolar valine in hemoglobin A?

    <p>Sickle cell anemia</p> Signup and view all the answers

    What is the isoelectric point (pI) of an amino acid?

    <p>The pH at which it carries equal positive and negative charges</p> Signup and view all the answers

    How do amino acids contribute to the buffering system in plasma proteins?

    <p>They can function as both acids and bases.</p> Signup and view all the answers

    What is the effect on amino acids at their isoelectric point when subjected to an electric current?

    <p>They precipitate in place due to neutrality.</p> Signup and view all the answers

    Which of the following amino acid characteristics best describes their amphoteric property?

    <p>Presence of both acidic and basic groups.</p> Signup and view all the answers

    Why is glutamate significant in the context of sickle cell anemia?

    <p>It is replaced by nonpolar valine in hemoglobin A.</p> Signup and view all the answers

    What stabilizing feature do polar side chains typically engage in within proteins?

    <p>Hydrogen bond formation.</p> Signup and view all the answers

    What is the consequence of amino acids existing as zwitterions in solution?

    <p>They exhibit no net charge.</p> Signup and view all the answers

    What type of carbohydrate is composed of 2-10 monosaccharide units?

    <p>Oligosaccharides</p> Signup and view all the answers

    Which type of monosaccharide is characterized by having a carbonyl group and can exist in various structural forms?

    <p>Aldose</p> Signup and view all the answers

    Which disaccharide is primarily derived from starch and hydrolyzed into two glucose molecules?

    <p>Maltose</p> Signup and view all the answers

    In the context of carbohydrates, what role does lactose play in nutrition?

    <p>It aids in the absorption of certain minerals</p> Signup and view all the answers

    Which monosaccharide is noted as having potential health implications related to blood types?

    <p>Galactose</p> Signup and view all the answers

    What is one of the distinctive properties of monosaccharides allowing them to exhibit isomerism?

    <p>Asymmetric carbon atoms</p> Signup and view all the answers

    Which carbohydrate is derived exclusively from the milk of mammals and consists of glucose and galactose?

    <p>Lactose</p> Signup and view all the answers

    What molecular formula represents carbohydrates generally, based on their fundamental components?

    <p>(CH2O)n</p> Signup and view all the answers

    What is the primary structural difference between saturated and unsaturated fatty acids?

    <p>Saturated fatty acids contain no double bonds, while unsaturated fatty acids contain one or more double bonds.</p> Signup and view all the answers

    What is the effect of introducing a cis double bond into a fatty acid structure?

    <p>It causes the fatty acid to bend or kink at that position.</p> Signup and view all the answers

    Which of the following statements about trans fatty acids is true?

    <p>They predominate in artificially produced foods.</p> Signup and view all the answers

    What is the main reason for the existence of zymogens in the body?

    <p>To prevent the activation of tissue-digesting enzymes prematurely</p> Signup and view all the answers

    What is the chain length range for medium chain fatty acids (MCFA)?

    <p>7-12 carbon atoms.</p> Signup and view all the answers

    How does the presence of double bonds affect the melting temperature of fatty acids?

    <p>It decreases the melting temperature.</p> Signup and view all the answers

    Which statement about allosteric modulation is true?

    <p>Allosteric enzymes have binding sites distinct from the active site.</p> Signup and view all the answers

    What is the primary regulation mechanism that results in rapid changes to enzyme activity?

    <p>Covalent modification by phosphorylation</p> Signup and view all the answers

    Which of the following fatty acid types is predominantly linked to health benefits like improved gut health?

    <p>Short chain fatty acids.</p> Signup and view all the answers

    What dietary sources are rich in cis double bonds?

    <p>Salmon, nuts, and olive oil.</p> Signup and view all the answers

    What characterizes feedback inhibition in metabolic pathways?

    <p>End products inhibit the committed-step enzyme activity.</p> Signup and view all the answers

    Which of the following statements best describes enzyme synthesis regulation?

    <p>It leads to changes in the concentration of enzymes over hours or days.</p> Signup and view all the answers

    What effect do long chain fatty acids (LCFA) have on their water solubility?

    <p>They are predominantly water insoluble.</p> Signup and view all the answers

    What characteristic is true regarding the distribution of fatty acid types in humans?

    <p>Most are saturated or monounsaturated fatty acids.</p> Signup and view all the answers

    How are medium chain fatty acids (MCFA) beneficial in diet compared to long chain fatty acids?

    <p>They provide higher satiety with fewer calories.</p> Signup and view all the answers

    What defines a prosthetic group in enzymes?

    <p>A non-protein component tightly bound to the enzyme</p> Signup and view all the answers

    Which statement about isoenzymes is correct?

    <p>They originated from different sites and have different physical properties.</p> Signup and view all the answers

    What role does the active site of an enzyme play?

    <p>It is involved in the binding of the substrate and catalysis.</p> Signup and view all the answers

    Which statement best describes the induced-fit model of enzyme-substrate interaction?

    <p>The binding of the substrate alters the shape of the enzyme.</p> Signup and view all the answers

    What typically characterizes the rate limiting step of enzymatic reactions?

    <p>It is the step that sets the pace for the entire reaction.</p> Signup and view all the answers

    What type of non-protein component acts as a cofactor for enzymes?

    <p>Inorganic ions such as Fe2+, Mn2+, or Zn2+</p> Signup and view all the answers

    Which of the following properties is NOT associated with enzymes?

    <p>They have a fixed shape that does not alter.</p> Signup and view all the answers

    What primarily motivates atoms to form chemical bonds?

    <p>To achieve a stable, low-energy state</p> Signup and view all the answers

    Which enzyme is primarily found in different forms such as LDH-1 and LDH-5?

    <p>Lactate dehydrogenase</p> Signup and view all the answers

    What impact does the active site of an enzyme have on substrate binding?

    <p>It ensures substrate specificity through shape complementarity.</p> Signup and view all the answers

    Which type of covalent bond is characterized by unequal sharing of electrons?

    <p>Polar covalent bond</p> Signup and view all the answers

    How do covalent bonds contribute to biological macromolecules?

    <p>They share electrons to stabilize structures</p> Signup and view all the answers

    Which statement accurately describes polar covalent bonds?

    <p>They favor the atom with higher electronegativity</p> Signup and view all the answers

    What is a primary characteristic of nonpolar covalent bonds?

    <p>Electrons are shared equally between atoms</p> Signup and view all the answers

    Which type of bond is considered the strongest and involves sharing of electrons?

    <p>Covalent bond</p> Signup and view all the answers

    Why are glycosidic bonds significant in biological molecules?

    <p>They link carbohydrates to each other or to other molecules</p> Signup and view all the answers

    What primarily differentiates covalent bonds from non-covalent bonds?

    <p>Covalent bonds are always stronger than non-covalent bonds</p> Signup and view all the answers

    In what context does a nonpolar covalent bond typically form?

    <p>Between two equitably electronegative atoms</p> Signup and view all the answers

    What is a significant impact of high levels of fructose consumption?

    <p>It may increase hunger and sugar cravings.</p> Signup and view all the answers

    Which polysaccharide serves as the main storage form of carbohydrates in animals?

    <p>Glycogen</p> Signup and view all the answers

    What component distinguishes amylopectin from amylose in starch?

    <p>Higher branching</p> Signup and view all the answers

    Which carbohydrate derivative is characterized by replacing a hydroxyl group with a hydrogen atom?

    <p>Deoxy-monsaccharide</p> Signup and view all the answers

    What role does fiber, such as cellulose, play in the human diet?

    <p>It aids the digestive system and prevents constipation.</p> Signup and view all the answers

    Which polysaccharide is primarily used as a plasma volume expander for intravenous infusion?

    <p>Dextrins</p> Signup and view all the answers

    Which of the following sugars is significant for detoxification in the liver?

    <p>Glucuronic acid</p> Signup and view all the answers

    What is the primary type of carbohydrate that humans cannot digest but is important in the diet?

    <p>Cellulose</p> Signup and view all the answers

    What characterizes competitive inhibition in enzyme-catalyzed reactions?

    <p>Increasing substrate concentration can reverse the inhibition.</p> Signup and view all the answers

    Which statement is true regarding non-competitive inhibition?

    <p>It can change the conformation of the enzyme without affecting substrate binding.</p> Signup and view all the answers

    In the context of enzyme regulation, what are inducers primarily responsible for?

    <p>Increasing the expression of specific genes coding for enzymes.</p> Signup and view all the answers

    What happens to the apparent Km of an enzyme during competitive inhibition?

    <p>It increases because the inhibitor binds to the active site competing with substrate.</p> Signup and view all the answers

    Which of the following best describes statin drugs in relation to enzyme inhibition?

    <p>They are competitive inhibitors due to structural similarity to the substrate.</p> Signup and view all the answers

    What characterizes long-chain fatty acids in relation to their carbon content?

    <p>They contain more than 12 carbon atoms.</p> Signup and view all the answers

    How can rancidity in lipids be effectively inhibited?

    <p>By adding antioxidants such as vitamins A and E.</p> Signup and view all the answers

    Which essential fatty acid is a precursor of ω-3 fatty acids?

    <p>α-linolenic acid.</p> Signup and view all the answers

    What is a common symptom of essential fatty acid deficiency in infants?

    <p>Hair loss.</p> Signup and view all the answers

    Which type of reaction leads to hydrolytic rancidity in fats?

    <p>Slight hydrolysis of fats.</p> Signup and view all the answers

    What is the main characteristic of cis double bonds in fatty acids?

    <p>They create a bend or kink in the fatty acid chain.</p> Signup and view all the answers

    Which characteristic distinguishes ω-6 fatty acids from ω-3 fatty acids?

    <p>The position of the first double bond relative to the ω end.</p> Signup and view all the answers

    Which type of fatty acids are primarily associated with an increased risk of atherosclerosis?

    <p>Trans fatty acids</p> Signup and view all the answers

    What major role do lipids play in biological membranes?

    <p>Forming structural elements.</p> Signup and view all the answers

    What is the role of medium chain fatty acids in diet?

    <p>They enhance gut health by eliminating harmful bacteria.</p> Signup and view all the answers

    What effect does the introduction of double bonds have on the melting temperature (Tm) of fatty acids?

    <p>It decreases the melting temperature.</p> Signup and view all the answers

    Which of the following foods is a primary source of ω-3 fatty acids?

    <p>Sardines.</p> Signup and view all the answers

    What is the energy yield of 1 gram of dietary lipids?

    <p>9 Cal.</p> Signup and view all the answers

    Which of the following correctly describes long chain fatty acids (LCFA)?

    <p>They must associate with protein for transport in circulation.</p> Signup and view all the answers

    What distinguishes trans double bonds from cis double bonds in fatty acids?

    <p>Trans double bonds have functional groups on opposite sides.</p> Signup and view all the answers

    Which condition is often associated with a deficiency of essential fatty acids?

    <p>Intellectual disability.</p> Signup and view all the answers

    What relationship exists between substrate concentration and enzyme activity once maximal velocity (Vmax) is reached?

    <p>Enzyme activity plateaus and does not increase further.</p> Signup and view all the answers

    Which statement about short chain fatty acids is true?

    <p>They can be produced from high-fiber foods.</p> Signup and view all the answers

    How does Km specifically indicate the affinity of an enzyme for its substrate?

    <p>A lower Km reflects a smaller substrate concentration needed for half-maximal velocity.</p> Signup and view all the answers

    How does chain length affect fatty acid properties?

    <p>Longer chains decrease water solubility.</p> Signup and view all the answers

    What occurs to salivary amylase when it enters an acidic environment such as the stomach?

    <p>It becomes denatured and loses its enzymatic function.</p> Signup and view all the answers

    What is a common source of medium chain fatty acids?

    <p>Coconut oil</p> Signup and view all the answers

    What characteristic of fatty acids helps maintain the fluid nature of membrane lipids?

    <p>Cis double bonds</p> Signup and view all the answers

    Which factor primarily influences the maximal velocity of an enzyme-catalyzed reaction?

    <p>The concentration of the enzyme available.</p> Signup and view all the answers

    What effect does an increase in substrate concentration have on enzymes before reaching Vmax?

    <p>The rate of reaction increases up to a certain point.</p> Signup and view all the answers

    Which statement accurately describes the process of enzyme denaturation?

    <p>Denaturation alters the shape of the enzyme, affecting function.</p> Signup and view all the answers

    At which substrate concentration level does an enzyme display half its maximal velocity (½ Vmax)?

    <p>At a concentration referred to as Km.</p> Signup and view all the answers

    What might occur if an enzyme is continuously exposed to extreme changes in pH?

    <p>The enzyme structure may be compromised, losing function.</p> Signup and view all the answers

    How is the initial reaction rate of an enzyme affected when substrate concentration is much lower than Km?

    <p>The reaction rate increases minimally with added substrate.</p> Signup and view all the answers

    Why do enzymes have an optimal pH range for activity?

    <p>To prevent enzyme denaturation from extreme conditions.</p> Signup and view all the answers

    Study Notes

    Pepsin and Maldigestion

    • Stomach acidity plays a crucial role in digestion, affecting the functionality of enzymes.
    • Aging, medications, and surgeries can lead to alterations in stomach acidity.
    • Reduced acidity can hinder the activity of pepsin, which is essential for protein digestion, resulting in maldigestion.

    Enzyme Function and pH

    • Enzymes are biological catalysts that function optimally within a specific pH range.
    • Extremes of pH can denature enzymes, causing them to lose their function.
    • Salivary amylase, an enzyme involved in starch digestion, is inactive in the stomach due to the acidic environment.
    • Optimal pH for salivary amylase is 6-8.

    Substrate Concentration and Enzyme Activity

    • Enzyme activity is directly influenced by substrate concentration, within a given pH and temperature range.
    • An increase in substrate concentration results in a higher enzyme activity and a faster reaction rate, up to a maximum velocity (Vmax).
    • Vmax represents the maximum rate of reaction when all enzyme active sites are saturated with substrate.
    • When the enzyme is saturated, any further increase in substrate concentration does not increase the rate of reaction.

    Km and Enzyme Affinity

    • Km represents the affinity of an enzyme for its substrate.
    • A low Km indicates a high affinity, meaning a lower substrate concentration is needed to reach half-maximal velocity (½ Vmax).
    • A high Km indicates a low affinity, requiring a higher substrate concentration to reach ½ Vmax.

    Enzyme Concentration and Reaction Rate

    • The rate of a reaction is directly proportional to the enzyme concentration, provided the substrate concentration is unlimited.
    • As enzyme concentration increases, the reaction rate increases until a maximum rate is reached.

    Product Concentration and Enzyme Activity

    • As product accumulates during a reaction, enzyme activity generally decreases.
    • This decrease may be due to:
      • Changes in the pH of the medium
      • Competition between product and substrate for the active site.
      • Product binding to the allosteric site (in the case of allosteric enzymes)

    Enzyme Regulation

    • Regulation of enzyme activity is crucial for maintaining cellular processes and adapting to changing needs.
    • Several mechanisms regulate enzyme activity, including:
      • Zymogen activation
      • Allosteric regulation
      • Covalent modification
      • Feedback inhibition

    Zymogen Activation

    • Some enzymes are secreted in an inactive form called proenzymes or zymogens.
    • Specific peptide bonds in the zymogen are hydrolyzed to activate the enzyme.
    • Examples include:
      • Pepsinogen to pepsin (protein digestion)
      • Trypsinogen to trypsin (protein digestion)
      • Plasminogen to plasmin (blood clot breakdown)

    Energy of Activation

    • Enzymes accelerate chemical reactions by lowering the energy of activation (Ea).
    • Ea is the amount of energy required for substrate molecules to reach the transition state.
    • Transition state is an unstable state where bond breaking and forming is most likely to occur.
    • Enzymes reduce Ea by providing an alternative pathway for the reaction.
    • The lower the Ea, the faster the reaction rate.

    Enzyme Classification

    • Enzymes are categorized into six main classes based on the type of reaction they catalyze:
      • Oxidoreductases
      • Transferases
      • Hydrolases
      • Lyases
      • Isomerases
      • Ligases

    Clinical Implications of Enzyme Regulation

    • Enzymes are frequently targeted by drugs; either activating or inhibiting them.
    • For example, tissue plasminogen activators (e.g., alteplase) activate plasminogen, a crucial protein in blood clot breakdown.
    • These drugs are used to dissolve blood clots in cases like myocardial infarction and stroke.

    Enzyme Activity as a Therapeutic Target

    • Enzyme activity represents a critical target for drug therapy, aiming to:
      • Enhance enzyme activity, as in the case of tissue plasminogen activators.
      • Inhibit enzyme activity, as in the case of drugs targeting certain cancer enzymes.
    • Understanding the regulation of enzyme activity provides a framework for designing targeted therapies.

    Zwitterion

    • A dipolar ion of an amino acid at its isoelectric point, in an aqueous medium.

    Clinical Implications of Amino Acids

    • Tyrosine: Precursor to thyroid hormone, adrenaline, nor-adrenaline, and melanin. Deficiency can cause hair and skin color loss.
    • Glutamine: Precursor to GABA (neurotransmitter). Severe deficiency can cause convulsions.
    • Hydroxy-containing amino acids: Play a role in signal transduction.
    • Sulfur-containing amino acids: Linked to obesity.
    • Branched chain amino acids (Valine, leucine, isoleucine): Useful for patients with liver diseases and bodybuilders.
    • Excessive intake of over-the-counter amino acids: Can lead to kidney failure.

    Proteins in Disease

    • Inborn errors of amino acid metabolism: Can cause mental retardation and blindness.
    • Defects in globin protein of hemoglobin: Can lead to hemolysis and oxygen delivery impairment.
    • Deficiency of immunoglobulins: Increases susceptibility to infections.
    • Defects in enzymes: Can lead to serious diseases, like glycogen storage diseases.
    • Defects in structural proteins (e.g., collagen): Can lead to skeletal deformities.
    • Defects in hormone production: Can lead to diseases like diabetes mellitus.
    • Deposition of abnormal proteins: Can cause diseases like Alzheimer's disease.
    • Deficiency of coagulation factors: Can lead to uncontrolled wound bleeding.

    Chemical Bonds

    • Bond: A force between neighboring atoms in a molecule or compound.
    • High energy bonds: Represented by the symbol "~".
    • Examples of high energy compounds: Phosphate compounds (ATP, ADP, GTP, etc.) and sulfur compounds (acetyl CoA, etc.).
    • Non-covalent bonds: Reversible and vital molecular interactions.
      • Ionic bonds: Involves a transfer of electrons, resulting in positively and negatively charged ions.
      • Electrostatic interactions: Attraction or repulsion between charged particles.
      • Hydrogen bonds: Electrostatic attraction between a hydrogen atom and an atom with a lone pair of electrons.

    Biomedical Importance of Ionic Bonds

    • Protein folding: Ionic bonds help shape tertiary and quaternary structures.
    • Catalytic reactions of enzymes: Ionic bonds are involved in enzyme catalysis.

    Enzyme Activity

    • Effect of pH: Enzymes have optimal pH ranges for activity. Extreme pH can lead to denaturation.
    • Effect of substrate concentration: Increasing substrate concentration increases enzyme activity until the active sites are saturated, reaching a maximum velocity (Vmax).
    • Km: The substrate concentration at which an enzyme reaches half its Vmax. Represents the enzyme's affinity for its substrate.
    • Zymogens: Inactive precursors of enzymes, preventing auto-digestion and coagulation.
    • Covalent modification: Regulation through addition or removal of phosphate groups, often by phosphorylation and dephosphorylation.
    • Allosteric modulation: Regulation by effectors binding to allosteric sites, altering enzyme activity.
    • Feedback inhibition: End-products inhibit the activity of an enzyme, often at the committed-step enzyme.
    • Enzyme synthesis: Regulation by altering the rate of enzyme synthesis (induction or repression).
    • Inhibitors: Substances that decrease the velocity of enzyme-catalyzed reactions.
      • Competitive inhibition: Inhibitor binds to the active site, competing with the substrate.
      • Non-competitive inhibition: Inhibitor binds to a site other than the active site causing conformational changes and inactivation.

    Fatty Acids

    • Long chain fatty acids contain over 12 carbon atoms and are the most prevalent in animal tissues and diets.
    • Most human fatty acids have an even number of carbon atoms (16, 18, or 20).
    • Longer fatty acids (> 22 carbons) are found in the brain.

    Rancidity

    • Rancidity is a process where lipids are exposed to light, heat, moisture, and bacteria.
    • This results in a change to the fat with a bad odour, taste, and an acidic reaction.
    • Rancidity involves:
      • Hydrolytic rancidity - short chain fatty acids are liberated due to slight hydrolysis, resulting in a bad odour.
      • Oxidative rancidity - unsaturated fatty acids are oxidized, forming peroxides, aldehydes, and ketones.
    • Rancidity is inhibited by adding antioxidants (e.g., vitamins A, E) and keeping fat in a clean, cold environment that is protected from light and moisture.

    Fatty Acids Numbering

    • Two numbering systems are used for carbon atoms in a fatty acid.

    Essential Fatty Acids (EFA)

    • While lipids can be derived from the diet or synthesized in the body, EFAs are essential for growth and development and must be obtained from the diet.
    • These include:
      • Linoleic acid: a precursor to ω-6 fatty acids, having a terminal double bond six bonds from the ω end.
      • α-linolenic acid: a precursor to ω-3 fatty acids, having a terminal double bond three bonds from the ω end.
    • ω-3 fatty acids are found in salmon, sardines, and flaxseeds, while ω-6 fatty acids are found in walnuts, peanuts, corn and sunflower oils.
    • EFA deficiency can cause hair loss, low platelets, and intellectual disability.

    Lipids in Health and Disease

    • Lipids act as:
      • Structural elements in biological membranes.
      • Energy stores, providing 9 Calories per gram.

    Amino Acids

    • Nonpolar amino acid side chains are found on the outside surface of proteins interacting with the lipid environment in a hydrophobic setting.
    • Polar amino acids participate in hydrogen bond formation that help stabilize protein structure.
    • Cysteine contains (-SH), an important component of enzyme active sites and helps form disulfide bridges.
    • Sickle cell anemia results from the replacement of polar glutamate with nonpolar valine at position six in hemoglobin A, leading to sticky red blood cells.

    Amphoteric Property of Amino Acids

    • Amino acids can behave as both acids and alkalis due to the presence of -COOH and -NH2 groups.
    • Neutral amino acids, as dipolar ions (Zwitterions), carry both negative and positive charges equally.
    • The isoelectric point (IEP) or pI is the pH where the amino acid has equal positive and negative charges.
    • At their IEP, amino acids do not migrate in an electric current and precipitate out of solution.
    • Plasma proteins, with their amphoteric property, act as a buffer system to maintain blood pH.

    Glycosidic Bond

    • Monosaccharides join together to form oligo and polysaccharides through glycosidic bonds between their carbon atoms.
    • The bond is named based on the involved carbons (e.g., 1-4) and labeled as α or β according to whether the hydroxyl group points up or down.
    • The position of the glycosidic bond influences how the body metabolizes it. For example, maltose (α 1-4) is digested in the body, while cellulose (β 1-4) is not.

    Peptide Bonds

    • They are strong covalent bonds forming between the amino group of one amino acid and the carboxylic group of another. Their formation and breakage require a significant amount of energy.
    • Peptide bond formation determines the primary structure of a protein.

    Ester Bonds

    • They form between the OH of an alcohol and the OH of a carboxylic group.
    • They are seen in:
      • Triacylglycerol formation from fatty acids and glycerol.
      • The formation of neurotransmitters (e.g., acetylcholine).
      • The structure of some drugs.
    • Ester bonds are broken down by esterase enzymes.

    Phosphodiester Bonds

    • They are formed between sugar carbons of nucleotides during DNA and RNA formation.

    Disulfide Bonds

    • These are sulfur-sulfur bonds formed within proteins through the oxidation of two cysteine residues. They can be formed between adjacent or distant cysteine moieties.
    • They are involved in stabilizing protein folds, enzyme catalysis, and protecting against oxidative damage.

    Double Bonds

    • This is a covalent bond with two shared electron pairs.
    • Unsaturated fatty acids present in olive oil have one or more double bonds.
    • Hydrogenation converts double bonds to single bonds during the production of margarine.

    High Energy Bonds

    • Their hydrolysis releases over 7 kcal of energy. They can drive energetically unfavorable reactions forward.
    • Carbohydrate metabolism, fatty acid oxidation, and amino acid oxidation produce these high-energy bonds.
    • High energy bonds are stored in compounds that release energy when needed like ADP and ATP.

    Enzymes

    • Enzymes speed up reactions by lowering the energy of activation.
    • The transition state (T*) is an unstable, high-energy state where the probability of bond breaking or forming is high.
    • The energy of activation (Ea) is the energy required to reach the transition state for all molecules in a mole.
    • Enzymes provide an alternative pathway with lower Ea, leading to a faster reaction rate.

    Enzyme Classification

    • Enzymes are classified into six main classes:
      • Oxidoreductases
      • Transferases
      • Hydrolases
      • Lyases
      • Isomerases
      • Ligases

    Clinical Implications of Enzymes

    • Enzymes are targets for drug action.
    • Enzyme activation:
      • Tissue plasminogen activators (e.g., alteplase) activate plasminogen to plasmin for clot breakdown.
    • Enzyme inhibition:
      • NSAIDs block cyclooxygenase and reduce pain and inflammation.
      • ACE inhibitors decrease blood pressure.
      • Statins inhibit cholesterol synthesis.

    Carbohydrates

    • Fructose is a type of sugar present in various fruits and provides a sweet taste.
    • Sucrose derivatives are sometimes used as alternatives to glucose for diabetics and obese patients.
    • High levels of fructose can increase hunger and sugar cravings.

    Polysaccharides

    • Glycogen is the branched form of polysaccharides from animal sources and the main storage form in humans.
    • Starch is the plant storage form of carbohydrates and is the most abundant type in the diet. It is found in potatoes, rice, and pasta.
    • Dextrins are highly branched and are used in intravenous infusion as plasma volume expanders to treat hypovolemic shock.
    • Cellulose is the structural form of carbohydrates in plants. Humans cannot digest cellulose, but it is consumed as fiber.
    • Fiber helps the digestive system to keep food moving through the gut and prevents constipation.

    Carbohydrate Derivatives

    • Deoxy-monosaccharides replace the –OH group with an –H group. An example is deoxyribose sugar, which is the sugar in DNA.
    • Amino sugars replace the –OH group with an –NH2 group. An example is glucosamine, which is found in proteoglycans.
    • Sugar acids replace the –CH2OH group with a –COOH group. An example is glucuronic acid, which is synthesized in the liver and plays a major role in detoxification.
    • Low levels of glucuronic acid in immature babies make them prone to jaundice due to bilirubin buildup.
    • Patients with liver failure are vulnerable to drug toxicity due to decreased glucuronic acid synthesis.
    • Sugar alcohols replace the COOH group with a CH2OH group. Examples include mannitol used as a diuretic and sorbitol used as an artificial sweetener.

    Importance of Carbohydrates

    • Carbohydrates provide dietary calories for most organisms and serve as a storage form of energy for the body.
    • They are a crucial component of cell membranes and mediate intercellular communication.
    • 1 gram of carbohydrates provides 4 calories.
    • Humans can obtain 100% of their daily energy requirements from proteins and fats.

    Role of carbohydrates in disease

    • Abnormal glucose metabolism is related to many diseases, including diabetes mellitus and certain types of cancer.
    • Inborn errors in carbohydrate metabolism can lead to a wide range of abnormalities, including mental retardation and hepatomegaly.

    Amino Acids

    • Most amino acids have a central carbon atom (α-carbon) with an attached hydrogen atom, an α-amino group (NH3+), an α-carboxyl group (COO–), and an R group (side chain).

    Classification of Amino Acids

    • Structure: Aliphatic (open chain of carbon and hydrogen) or aromatic (contain benzene ring)
    • Charge: Neutral, acidic (negative charge at physiologic pH), or basic (positive charge at physiologic pH)
    • Biological Importance: Essential, non-essential, or semi-essential
    • Polarity: Non-polar (hydrophobic, neutral) or polar (hydrophilic, can be neutral, acidic, or basic)

    Non-Polar Amino Acids

    • Non-polar amino acids cluster together in the interior of proteins to avoid water.
    • This phenomenon, known as the hydrophobic effect, gives the protein its three-dimensional shape.

    Enzyme Regulation

    • Zymogens: Protective mechanism to prevent auto-digestion of tissue producing digestive enzymes and prevent intravascular coagulation of blood.
    • Covalent Modification: Regulation by the addition or removal of phosphate groups to serine or tyrosine residues on the enzyme chain.
    • Allosteric Modulation: Enzymes bind to small, regulatory molecules called effectors at distinct allosteric sites. Effectors can be positive (increase catalytic activity) or negative (reduce catalytic activity).
    • Feedback Inhibition: End products inhibit enzyme activity, often at the committed-step enzyme, which is the first irreversible enzyme unique to the pathway.
    • Enzyme Synthesis: Cells can regulate the amount of enzyme present by altering the rate of enzyme synthesis. Induction leads to increased enzyme synthesis, while repression leads to decreased synthesis.

    Clinical Implications of Enzyme Regulation

    • Lead can non-competitively inhibit enzymes in the heme synthesis pathway, leading to anemia.
    • Reducing agents like vitamin C and vitamin E can restore enzyme activity.

    Enzyme Poison (Irreversible Inhibition)

    • Inhibitors bind covalently and irreversibly to the functional group of the enzyme, destroying it.
    • This type of inhibition decreases Vmax while Km remains unchanged.
    • Examples include organophosphates found in pesticides and cyanide.

    Enzymes in Clinical Use

    • Enzymes can be used to diagnose diseases by measuring their levels in plasma.
    • Functional Plasma Enzymes: Enzymes secreted into the plasma by certain organs and perform specific functions. Example: liver secretes zymogens involved in blood coagulation.
    • Non-Functional Plasma Enzymes: Intracellular enzymes released from cells during normal turnover. Their levels represent the steady state equilibrium between release and removal from plasma. Elevated levels can indicate tissue damage.

    Enzyme Activity and Factors Affecting it

    • Extreme pH levels can disrupt the shape of an enzyme, causing it to lose its function. This is known as denaturation.

    • Maximal velocity (Vmax) represents the highest rate at which an enzyme can catalyze a reaction. It occurs when all active sites of the enzyme are saturated with substrate.

    • A low Km value suggests a high affinity of the enzyme for its substrate. This means that the enzyme can achieve a high reaction rate even at low substrate concentrations.

    • Substrate concentration directly impacts enzyme activity. Increasing substrate levels generally leads to increased reaction rate until all active sites are saturated, reaching Vmax.

    • Aging primarily affects pepsin enzyme function by reducing its overall activity.

    • Salivary amylase exhibits optimal activity at a pH around 6.8.

    • When all active sites of an enzyme are occupied, the enzyme is working at its maximum capacity (Vmax).

    • Extremes of temperature generally impact enzyme activity negatively. High temperatures can denature enzymes, while low temperatures lead to reduced activity.

    • The plateau in reaction rate at high substrate concentrations indicates that the enzyme is saturated with substrate, meaning that all active sites are occupied, and further increases in substrate concentration will not lead to a faster reaction rate.

    • A decrease in temperature generally slows down enzyme activity, but it does not denature the enzyme.

    • pH affects enzyme activity by influencing the shape and charge of the enzyme. Each enzyme has an optimal pH range for maximum activity outside which its structure may be compromised.

    • Increasing substrate concentration primarily increases enzyme activity, up to a certain point where all active sites are occupied and the reaction rate plateaus, reaching Vmax.

    • The primary consequence of enzyme denaturation is the loss of its biological activity.

    • Vmax is defined as the maximum rate of an enzyme-catalyzed reaction when the enzyme is saturated with substrate.

    • As the temperature approaches the enzyme's optimal temperature, the activity typically increases. However, beyond the optimal temperature, enzyme activity begins to decrease due to denaturation.

    • A change in the Vmax of an enzyme reaction is most likely caused by a factor that alters the enzyme's concentration or its ability to bind to the substrate, such as a change in pH, the presence of inhibitors, or a change in the enzyme's structure.

    • When substrate concentration is much lower than the Km value, the rate of an enzyme-catalyzed reaction is primarily governed by the substrate concentration.

    • When substrate concentration is much greater than Km, the rate of an enzymatic reaction approaches Vmax and becomes almost independent of further increases in substrate concentration.

    • A decrease in pH usually leads to a decrease in enzyme activity because it alters the enzyme's shape and charge, potentially disrupting its catalytic activity.

    Zymogens and Enzyme Activation

    • Zymogens are inactive precursors of enzymes that are activated only when needed. They are essential for controlling enzyme activity and preventing damage to cells or tissues.
    • The activation of zymogens involves a conformational change that exposes their active site, allowing them to catalyze their specific reactions.

    Enzyme Concentration and Reaction Rate

    • When substrate is unlimited, the reaction rate is directly proportional to the enzyme concentration. This means that doubling the enzyme concentration will double the reaction rate.

    Vmax and Enzyme Kinetics

    • Vmax represents the maximum rate at which an enzyme can catalyze a reaction. It occurs when all active sites of the enzyme are saturated with substrate.

    First-Order Reactions

    • A first-order reaction in enzyme kinetics is characterized by its rate being directly proportional to the substrate concentration, particularly when substrate concentration is much lower than Km.

    Enzyme Denaturation and its Determinants

    • Enzyme denaturation is the process of unfolding and losing the enzyme's functional three-dimensional structure, resulting in the loss of its activity.
    • Factors that DO NOT affect enzyme denaturation include changes in the concentration of the product or the presence of cofactors or coenzymes.
    • Factors that CAN affect enzyme denaturation include extremes of temperature (high or low), pH changes, and the presence of certain chemicals or detergents.

    Enzyme Activity and Product Accumulation

    • As product accumulates, an enzyme's activity may decrease due to:
      • Product inhibition where the product binds to the active site, preventing further substrate binding.
      • Feedback inhibition where the product of a reaction acts as an inhibitor on an earlier step in the pathway.

    Protein Structure and Bonding

    • The general shape of protein is maintained by various types of bonds, including:
      • Hydrogen bonds: contribute to the overall structure, particularly in secondary structures like alpha helices and beta sheets.
      • Disulfide bonds: strong covalent bonds formed between cysteine residues, stabilizing protein structure.
      • Ionic bonds: electrostatic interactions between oppositely charged amino acid side chains.
      • Hydrophobic interactions: non-covalent interactions between nonpolar amino acid side chains, driven by their tendency to avoid water.

    High Energy Bonds

    • High energy bonds store a large amount of energy, which is released when the bond is broken.
    • ATP (adenosine triphosphate) is considered a high energy compound due to the presence of high energy phosphate bonds.
    • The hydrolysis of ATP releases energy that can be used to power cellular processes.

    Ionic Bonds

    • Ionic bonds are strong electrostatic attractions between oppositely charged ions. They play a critical role in protein structure and function, contributing to the stability of the overall structure and influencing interactions with other molecules.

    Hydrogen Bonds

    • Hydrogen bonds are weaker than covalent bonds but still play a crucial role in biological systems. They involve the electrostatic attraction of a hydrogen atom, covalently bonded to a highly electronegative atom like oxygen or nitrogen, towards another electronegative atom.

    Biomedical Significance of Ionic Bonds in Proteins

    • Ionic bonds contribute to the stability of protein structure and function.
    • They play a significant role in protein folding and interactions with other molecules, influencing the folding patterns and binding events involved in various biological processes.

    ATP: The Energy Currency of Metabolism

    • ATP (adenosine triphosphate) is the primary energy currency in metabolism. It transfers energy released from the breakdown of food molecules into energy-requiring processes like muscle contraction and biosynthesis.

    Non-Covalent Bonds

    • Non-covalent bonds are weaker than covalent bonds and play essential roles in biological systems.
    • They often involve weaker electrostatic attractions or interactions between molecules.
    • Characteristics of non-covalent bonds:
      • They are weaker than covalent bonds.
      • They are easily broken and reformed.
      • They are responsible for many biological interactions, including protein folding, enzyme-substrate binding, and DNA replication.

    Enzyme Inhibition

    • Competitive inhibition occurs when an inhibitor molecule competes with the substrate for binding at the enzyme's active site. This increases the apparent Km of the enzyme, effectively reducing the enzyme's affinity for its substrate.

    • Non-competitive inhibition occurs when an inhibitor molecule binds to a site on the enzyme different from the active site. This reduces the enzyme's Vmax without affecting its Km.

    • The addition of a competitive inhibitor to an enzyme reaction causes a decrease in the reaction rate, which can be reversed by increasing the substrate concentration.

    • Inhibitors in enzymatic reactions are substances that interfere with the enzyme's catalytic activity, reducing the rate of the reaction.

    • Statin drugs are considered competitive inhibitors in cholesterol biosynthesis because they bind to the active site of HMG-CoA reductase, the enzyme responsible for cholesterol synthesis, blocking the production of cholesterol.

    Glutamine Deficiency and its Consequences

    • A severe deficiency of glutamine in the body can lead to various metabolic disorders, including:
      • Impaired brain function: Glutamine is a key neurotransmitter and is involved in many brain functions, including memory and learning. A deficiency can lead to impaired cognitive function.
      • Muscle wasting: Glutamine is important for muscle growth and repair. A deficiency can lead to muscle wasting and weakness.
      • Immune dysfunction: Glutamine plays a role in immune function. A deficiency can weaken the immune system, making individuals more susceptible to infections.

    Non-Competitive Inhibition and its Impact on Vmax

    • A non-competitive inhibitor reduces the enzyme's Vmax without affecting its Km. This means that it decreases the maximum rate of the reaction but does not affect the enzyme's affinity for its substrate.

    Obesity and Amino Acids

    • Obesity is linked to the amino acid leucine. A higher intake of leucine can promote fat storage and hinder fat breakdown, contributing to obesity.

    Enzyme-Substrate Complex in Competitive Inhibition

    • In competitive inhibition, the inhibitor molecule forms a complex with the enzyme at the active site, blocking the binding of the substrate.

    Globin Protein Defects and Hemoglobinopathy

    • Defects in the globin protein of hemoglobin can lead to hemoglobinopathies, such as sickle cell anemia and thalassemias. These genetic disorders affect the structure and function of hemoglobin, leading to various health problems.

    Distinguishing Non-Competitive from Competitive Inhibitors

    • Non-competitive inhibitors bind to a site on the enzyme different from the active site, affecting its overall catalytic activity. While competitive inhibitors bind to the active site, directly competing with the substrate for binding.

    Immunoglobulin Deficiency and its Consequences

    • A deficiency of immunoglobulins in the body can lead to immunodeficiency disorders, making individuals more susceptible to infections and diseases.

    Excessive Amino Acid Intake and its Potential Consequences

    • Excessive intake of over-the-counter amino acids, especially in athletes, can lead to various issues:
      • Kidney stress: The kidneys are responsible for filtering waste products, including excess amino acids. Overloading the kidneys can lead to damage and impaired function.
      • Metabolic imbalances: High levels of specific amino acids can disrupt the balance of other nutrients in the body, potentially leading to health problems.
      • Gastrointestinal discomfort: Excess amino acid intake can cause digestive issues like bloating, gas, and diarrhea.

    Inborn Errors in Amino Acid Metabolism

    • Inborn errors in amino acid metabolism can result in the accumulation of specific amino acids in the body, causing various health problems:
      • Mental retardation: Some amino acid disorders can impair brain development and function, leading to intellectual disabilities.
      • Liver damage: The liver plays a crucial role in amino acid metabolism. Accumulation of specific amino acids can damage the liver.
      • Other health issues: Specific amino acid disorders can lead to diverse health problems, including seizures, developmental delays, and heart problems.

    Roles of Hydroxy-Containing Amino Acids

    • Hydroxy-containing amino acids play various essential roles in the body:
      • Collagen synthesis: Hydroxyproline and hydroxylysine are essential components of collagen, a crucial protein for connective tissues, skin, and bones.
      • Neurotransmitter function: Serine and threonine are involved in the synthesis of neurotransmitters like acetylcholine.
      • Enzyme activity: Hydroxy-containing amino acids can contribute to the active site of certain enzymes, influencing their catalytic activity.

    Abnormalities in Structural Proteins

    • Abnormalities in structural proteins, such as collagen, can lead to issues with connective tissues and skeletal development:
      • Osteogenesis imperfecta: A genetic disorder affecting collagen synthesis, resulting in brittle bones, fragile skin, and other skeletal abnormalities.
      • Ehlers-Danlos syndromes: A group of inherited disorders affecting various types of collagen, leading to joint hypermobility, skin elasticity issues, and other health problems.

    Role of Zymogens

    • Zymogens, also known as proenzymes, are inactive precursors of enzymes, playing a crucial role in controlling enzyme activity. They allow for specific activation only when needed, preventing unnecessary damage or unwanted reactions.

    Significance of Allosteric Sites on Enzymes

    • Allosteric sites are binding sites on enzymes located away from the active site. They regulate enzyme activity by influencing the conformational changes that occur at the active site, leading to either activation or inhibition.

    Feedback Inhibition

    • Feedback inhibition occurs in metabolic pathways where the end product of the pathway inhibits the activity of an early enzyme in the pathway. This helps to maintain the balance of metabolic intermediates and prevents overproduction of unwanted byproducts.

    Regulation of Enzyme Synthesis

    • Enzyme synthesis can be regulated by changes in cellular conditions, such as nutrient availability, hormone levels, and other cellular signals.
    • This regulation allows for precise control of enzyme production and activity, ensuring a proper balance of metabolic processes.

    Committed-Step Enzyme

    • The committed-step enzyme in a metabolic pathway is the first enzyme that is unique to that pathway. It is the point where regulation of the pathway occurs, determining the rate of the entire process.

    Allosteric Enzyme Effectors

    • Activators are effectors that enhance the catalytic activity of allosteric enzymes. They bind to the allosteric site and induce a conformational change that increases the enzyme's affinity for its substrate.
    • Inhibitors are effectors that reduce the catalytic activity of allosteric enzymes. They bind to the allosteric site and induce a conformational change that decreases the enzyme's affinity for its substrate.

    Short-Term vs. Long-Term Regulation of Enzyme Activity

    • Short-term regulation of enzyme activity typically involves rapid adjustments to the enzyme's activity, such as:
      • Allosteric regulation: Binding of activators or inhibitors to allosteric sites.
      • Covalent modification: Changes in the enzyme's structure through the addition or removal of chemical groups.
    • Long-term regulation of enzyme activity involves changes in enzyme production:
      • Transcriptional regulation: Control of gene expression to regulate the synthesis of enzymes.
      • Translational regulation: Control of the translation of mRNA into proteins.

    Increasing Substrate Concentration and Vmax

    • Increasing substrate concentration generally enhances enzyme activity, leading to an increase in the reaction rate. However, when approaching Vmax, further increases in substrate concentration have a smaller impact on the reaction rate because nearly all active sites are already occupied.

    High Km Value and Enzyme Affinity

    • A high Km value signifies a low affinity of the enzyme for its substrate. This means the enzyme requires a higher concentration of substrate to reach half of its maximum velocity (Vmax), suggesting that the enzyme binds weakly to its substrate.

    Factors Affecting Reaction Velocity

    • Factors that DO affect the reaction velocity of an enzyme-catalyzed reaction include:
      • Temperature
      • pH
      • Enzyme concentration
      • Substrate Concentration
      • Presence of inhibitors or activators

    Denaturation and Substrate Interaction

    • Denaturation disrupts the enzyme's three-dimensional structure, leading to a loss of function and the inability to interact properly with its substrate.

    First-Order Reactions and Reaction Conditions

    • A reaction appears to be first-order when the substrate concentration is much lower than the Km value. This means the reaction rate is directly proportional to the substrate concentration.

    Enzyme Activity Outside Optimal pH

    • When exposed to an environment outside its optimal pH range, an enzyme's activity is likely to decrease, potentially leading to denaturation and a loss of function.

    Significance of Achieving Maximal Velocity

    • Reaching maximal velocity (Vmax) in an enzyme-catalyzed reaction indicates that all active sites of the enzyme are saturated with substrate. Further increases in substrate concentration will not lead to an increase in the reaction rate.

    Plateau in Enzyme Kinetics

    • The "plateau" in enzyme kinetics refers to the point where the reaction rate reaches its maximum (Vmax) and no longer increases despite adding more substrate. This signifies that all active sites of the enzyme are occupied.

    α and β Designations in Glycosidic Bonds

    • The α or β designation in glycosidic bonds refers to the configuration of the anomeric carbon atom.
    • α-glycosidic bonds have the anomeric hydroxyl group on the same side of the pyranose ring as the CH2OH group at carbon 6.
    • β-glycosidic bonds have the anomeric hydroxyl group on the opposite side of the pyranose ring as the CH2OH group at carbon 6.

    Digestion of Maltose vs. Cellulose

    • Maltose can be digested by the body because it has α-glycosidic bonds that can be broken down by human enzymes, like the enzyme maltase.
    • Cellulose, on the other hand, has β-glycosidic bonds that cannot be broken down by human enzymes.

    Peptide Bond Formation

    • Peptide bonds are formed through a dehydration reaction between the carboxyl group of one amino acid and the amino group of another amino acid, releasing a water molecule.

    Characteristics of Ester Bonds

    • Ester bonds are formed by the reaction of an alcohol and a carboxylic acid, with the elimination of a water molecule.
    • They are commonly found in triglycerides, the primary form of stored energy in the body.

    Acetylcholine Breakdown

    • Acetylcholine is a neurotransmitter that transmits signals across nerve synapses.
    • The enzyme acetylcholinesterase is responsible for the rapid breakdown of acetylcholine, ensuring efficient nerve impulse transmission.

    Consequence of Peptide Bond Denaturation

    • Peptide bond denaturation in proteins can result in the disruption of the protein's structure, ultimately leading to loss of function.

    Glycosidic Bond Formation

    • The formation of a glycosidic bond between two monosaccharides results in the creation of a disaccharide or a longer oligosaccharide or polysaccharide.

    High Energy Bonds and Their Characteristics

    • High energy bonds require a large amount of energy for both formation and breakage.
    • They are broken through hydrolysis, releasing the stored energy for cellular processes.

    Predominant Fatty Acids in Humans

    • Saturated fatty acids and unsaturated fatty acids, both monounsaturated and polyunsaturated, primarily occur in the human body.

    Rancidity in Fats

    • Rancidity in fats is caused by the oxidation of unsaturated fatty acids, leading to the formation of off-flavors and odors.

    Essential Fatty Acids and Their Significance

    • Essential fatty acids are fatty acids that the body cannot synthesize and must be obtained from the diet.
    • They are essential for growth and development and play various roles in the body, including:
      • Brain function: Essential fatty acids are crucial for brain development and function.
      • Immune function: They support the immune system and help fight inflammation.

    Inhibition of Rancidity

    • Antioxidants can help inhibit rancidity in lipids by preventing the oxidation of unsaturated fatty acids.

    Essential Fatty Acid Deficiency in Infants

    • Essential fatty acid deficiency in infants can lead to impaired growth and development. Symptoms include:
      • Dry skin and hair: Essential fatty acids are important for healthy skin and hair.
      • Poor wound healing: Essential fatty acids are involved in the process of wound healing.
      • Impaired vision: Essential fatty acids are crucial for retinal function.

    Dietary Lipid Roles

    • Dietary lipids play a significant role in providing energy, promoting hormonal function, forming cell membranes, and contributing to the absorption of fat-soluble vitamins.

    Characteristics of Omega-3 Fatty Acids

    • Omega-3 fatty acids are polyunsaturated fatty acids characterized by the presence of a double bond at the third carbon atom from the methyl end of the fatty acid chain.

    Dietary Fatty Acid Determination

    • The types of fatty acids present in an individual's diet are primarily determined by the types of foods consumed, including animal products, plant oils, and processed foods.

    Impact of Amino Acid Substitution in Hemoglobin

    • Replacing polar glutamate with nonpolar valine in hemoglobin A causes the formation of sickle cell hemoglobin. This alteration affects hemoglobin's structure and function, leading to the formation of sickle-shaped red blood cells, hindering oxygen transport and causing complications.

    Role of Polar Side Groups in Proteins

    • Polar side groups in amino acids contribute to protein structure and function by:
      • Facilitating hydrogen bonding: contributing to the overall stability and structure of the protein.
      • Creating hydrophilic surfaces: allowing proteins to interact with water and other polar molecules.

    Amino Acid Behavior in Solution

    • Amino acids behave as amphoteric substances in solution because they can act as both acids and bases. This is due to the presence of both a carboxyl group (COOH) and an amino group (NH2) in their structure.

    Isoelectric Point of Amino Acids

    • The isoelectric point (IEP) of an amino acid is the pH at which the amino acid exists as a zwitterion, with a net charge of zero.

    Complete Ionization of Amino Acids

    • The complete ionization of neutral amino acids results in the formation of a zwitterion, where the amino group is protonated (+NH3) and the carboxyl group is deprotonated (-COO-).

    Role of Cysteine in Proteins

    • Cysteine, with its sulfur-containing thiol group, plays a crucial role in protein structure and function:
      • Disulfide bond formation: The thiol group allows for the formation of disulfide bonds, which are essential for stabilizing protein structure and function.
      • Active site component: The thiol group can be part of the active site of enzymes, influencing their catalytic activity.

    Amphoteric Properties and Plasma Proteins

    • The amphoteric properties of plasma proteins are vital for maintaining the pH balance of blood. They act as buffers, resisting changes in blood pH to keep it within a narrow range.

    Influence of Nonpolar R Groups on Proteins

    • Nonpolar R groups in a protein tend to cluster together in a hydrophobic environment, minimizing their contact with water molecules. This helps stabilize the protein's structure and shape.

    Function of Disulfide Bonds in Proteins

    • Disulfide bonds, formed between cysteine residues, play an essential role in:
      • Stabilizing protein structure: They act as strong cross-links, maintaining the protein's three-dimensional shape.
      • Influencing biological activity: They can influence protein function by affecting folding, interaction with other proteins, and stability.

    High Energy Bonds

    • High energy bonds are chemical bonds that store a large amount of energy, which is released when the bond is broken.
    • They are commonly found in molecules like ATP (adenosine triphosphate) and other energy-rich molecules.

    Unsaturated Fatty Acids and Human Health

    • Unsaturated fatty acids, particularly omega-3 fatty acids and omega-6 fatty acids, are essential for human health.
    • They play crucial roles in brain function, reducing inflammation, and promoting cardiovascular health.

    Double Bonds in Biological Molecules

    • Double bonds in biological molecules, particularly in unsaturated fatty acids, play a significant role:
      • Affecting physical properties: They make the molecule more fluid and less likely to solidify at room temperature, like in oils.
      • Providing flexibility: They can rotate freely, allowing for greater flexibility in the molecule.

    Hydrogenation

    • Hydrogenation is a process that involves adding hydrogen atoms to the double bonds of unsaturated fatty acids. This process saturates the fatty acids, making them more solid at room temperature and increasing their shelf life.

    Phosphodiester Bonds in Nucleic Acids

    • Phosphodiester bonds are responsible for linking nucleotides together in nucleic acids (DNA and RNA). They are formed between the phosphate group of one nucleotide and the 3'-hydroxyl group of the previous nucleotide. This linkage creates the backbone of nucleic acid molecules.

    Disulfide Bonds in Biological Systems

    • Disulfide bonds play a crucial role in biological systems:
      • Protein stabilization: They contribute significantly to protein stability and structure, particularly in extracellular proteins.
    • Important for the function: They can influence protein activity by affecting protein folding, interaction with other proteins, and overall stability.

    Oxidation of Thiol Groups

    • The oxidation of thiol groups in cysteine residues can lead to the formation of disulfide bonds. This process is important for protein folding and stability.

    Enzyme Function and Activation Energy

    • Enzymes play a crucial role in chemical reactions by lowering the energy of activation (Ea), the energy barrier needed for a reaction to occur.
    • This decrease in Ea speeds up the reaction rate, making the process more efficient.

    Transition State in Chemical Reactions

    • The transition state represents the highest energy point in a chemical reaction, forming an unstable intermediate between reactants and products.
    • Reaching the transition state is crucial for the reaction to occur. Enzymes can lower the energy required to reach the transition state, increasing the reaction rate.

    Impact of Lowering Ea

    • Lowering the energy of activation (Ea) allows the reaction to proceed faster, requiring less energy input. This increases the reaction rate and makes the process more efficient.

    Carbohydrates

    • Carbohydrates are hydrates of carbon containing hydrogen and oxygen in a ratio of 2:1 with the general formula (CH2O)n where n > 3

    • Carbohydrates play a crucial role in our survival and function.

    • Carbohydrates are classified into three categories:

      • Monosaccharides (mono = one)
      • Oligosaccharides (oligo = few) 2-10 monosaccharide units
      • Polysaccharides (poly = many) > 10 monosaccharide units

    Monosaccharides (Simple Sugars)

    • Monosaccharides are named based on the number of carbon atoms:

      • Trioses (C3)
      • Tetroses (C4)
      • Pentoses (C5)
      • Hexoses (C6)
      • Heptoses (C7)

    • The most abundant monosaccharides in nature are 6-carbon sugars like glucose and fructose.

    • Monosacchardies either contain an aldehyde group and are called aldoses or a keto group and are called ketoses.

    • The carbon atom double bonded to an oxygen atom forms a carbonyl group.

    Physical Properties of Monosaccharides

    • An asymmetric carbon atom is a carbon atom attached to four different groups or atoms.

    • Asymmetric carbon atoms allow for the existence of isomers.

    • Isomers are compounds with the same chemical formula but different structures.

    • Fructose, glucose, and galactose all have the same chemical formula (C6H12O6) but are isomers.

    Oligosaccharides

    • The most abundant oligosaccharides are disaccharides.

    • There are three key disaccharides:

      • Maltose: Malt sugar, a product of starch degradation, hydrolyzed to two glucose molecules.
      • Lactose: Composed of glucose and galactose subunits, found exclusively in the milk of mammals (milk sugar), the least sweet sugar.
      • Sucrose: Composed of glucose and fructose subunits, also known as cane sugar.

    Lactose Intolerance

    • Some individuals are unable to fully digest the lactose in milk, leading to diarrhea, gas, and bloating after consuming dairy products.

    • Lactose free dairy products are available for those with lactose intolerance.

    Lipids

    • Lipids are organic compounds generally insoluble in water but soluble in organic solvents.

    • Include fats, oils, waxes, phospholipids, and steroids.

    • Lipids function as:

      • Energy storage
      • Structural components of cell membranes
      • Hormones
      • Insulation
      • Cushioning of organs

    Fatty Acids

    • Fatty acids are long-chain carboxylic acids.

    • They are classified based on the presence and number of double bonds:

      • Saturated fatty acids: No double bonds, solid at room temperature (e.g., butter, lard).
      • Unsaturated fatty acids: One or more double bonds, liquid at room temperature (e.g., olive oil, vegetable oil).

    Long-Chain Fatty Acids

    • Contain more than 12 carbon atoms.

    • Palmitic acid (16 C) is one of the most abundant fatty acids in animal tissues and diets.

    • In humans, fatty acids with an even number of carbon atoms (16, 18, or 20) are most common, while longer fatty acids (> 22 carbons) are found in the brain.

    Rancidity

    • Lipids exposed to light, heat, moisture, and bacterial action can become rancid.

    • Rancid fat has a bad odor and taste and is acidic in reaction.

    • Two types of rancidity:

      • Hydrolytic rancidity: Hydrolysis of fat, releasing short-chain volatile fatty acids with bad odor.
      • Oxidative rancidity: Oxidation of unsaturated fatty acids, producing peroxides, aldehydes, and ketones.

    • Rancidity can be inhibited by:

      • Adding antioxidants like vitamins A and E
      • Storing fat in a cold, clean place away from light and moisture

    Fatty Acid Numbering

    • Two systems for numbering the carbon atoms in a fatty acid:
      • Greek-letter system: Carbon nearest to the carboxyl end is designated as α, the terminal carbon as ω.
      • Δ system: Double bonds are located by the number of the first carbon atom followed by Δ.

    Essential Fatty Acids (EFAs)

    • Lipids can be obtained from the diet or synthesized de novo.

    • Essential fatty acids (EFAs) must be provided in the diet.

    • Two key EFAs:

      • Linoleic acid: Precursor of ω-6 fatty acids, important for growth and development.
      • α-linolenic acid: Precursor of ω-3 fatty acids, important for growth and development.

    • ω-6 fatty acids: Found in walnuts, peanuts, corn, and sunflower oils.

    • ω-3 fatty acids: Found in salmon, sardines, and flaxseeds.

    • Deficiencies in EFAs can lead to:

      • Hair loss
      • Low platelet count
      • Intellectual disability

    Lipids in Health and Disease

    • Lipids play crucial roles in health:

      • Structural elements in biological membranes.
      • Store and provide energy (1 gram of dietary lipids provides about 9 Calories).

    • Diseases related to lipids:

      • Obesity
      • Cardiovascular disease
      • Cancer

    Enzymes

    • Enzymes are biological catalysts that accelerate the rate of chemical reactions without being consumed in the process.

    • Enzymes enhance reaction rates by lowering the free energy of activation (Ea).

    • The transition state is an unstable state where the probability of making or breaking a chemical bond to form a product is very high.

    • The energy of activation (Ea) is the amount of energy required to bring all the molecules in one gram-mole of a substrate to the transition state.

    • In the absence of an enzyme, only a small proportion of substrate molecules have enough energy to reach the transition state.

    • Enzymes provide an alternative pathway for a reaction with a lower Ea, speeding up the reaction.

    • Enzymes bind transiently with the substrate to form a transient state with lower energy of activation than the substrate alone.

    • After product formation, the enzyme is free to bind with another substrate molecule.

    Classification of Enzymes

    • Six main classes:

      • Oxidoreductases: Catalyze oxidation-reduction reactions.

      • Transferases: Catalyze group transfer reactions.

      • Hydrolases: Catalyze hydrolysis reactions.

      • Lyases: Catalyze cleavage of C-C, C-O, C-N, and other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds.

      • Isomerases: Catalyze intramolecular rearrangements.

      • Ligases: Catalyze the joining of two molecules coupled with the hydrolysis of ATP.

    Clinical Implications of Enzymes

    • Enzymes are important drug targets:

      • Enzyme activation: e.g., Tissue plasminogen activators (alteplase) activate plasminogen to plasmin, breaking down fibrin clots in conditions like myocardial infarction or ischemic stroke.

      • Zymogens: Precursor forms of enzymes that prevent auto-digestion of tissues and intravascular coagulation of blood.

    Regulation of Enzyme Activity

    • Enzymes are regulated by multiple mechanisms:

      • Covalent Modification: Phosphorylation and dephosphorylation can activate or inactivate enzymes.

      • Allosteric Modulation: Binding of effectors to allosteric sites can alter enzyme activity.

      • Feedback Inhibition: End products inhibit the activity of the enzyme, typically at the committed-step enzyme in a pathway.

      • Enzyme Synthesis: Cells can regulate the amount of enzyme present by altering the rate of enzyme synthesis.

    Inhibitors

    • Inhibitors are substances that decrease the velocity of an enzyme-catalyzed reaction.

    • Two main types of inhibition:

      • Competitive Inhibition: The inhibitor binds to the same site as the substrate, competing for active site binding.

      • Non-Competitive Inhibition: The inhibitor binds to a different site on the enzyme, altering the enzyme's conformation and inactivating the catalytic site.

    Fatty Acid Structure

    • Long chain fatty acids (LCFA) are highly water insoluble and require protein association for transport in the bloodstream.
    • Saturated fatty acids lack double bonds, while unsaturated fatty acids contain one or more double bonds, also known as mono- and polyunsaturated fatty acids.
    • Cis double bonds occur when functional groups are on the same side of the double bond, causing a bend or kink in the fatty acid chain.
    • Trans double bonds occur when functional groups are on opposite sides of the double bond, found primarily in artificially produced foods and linked to an increased risk of atherosclerosis.
    • Increased double bond presence generally lowers the melting temperature of fatty acids.
    • Increasing chain length generally increases the melting temperature.
    • The presence of double bonds in fatty acids helps maintain membrane fluidity.

    Fatty Acid Chain Length

    • Short-chain fatty acids (SCFA) contain 2-6 carbon atoms. SCFA are produced by the human body from high-fiber food sources.
    • Medium-chain fatty acids (MCFA) contain 7-12 carbon atoms and are found mainly in coconut oil and dairy products.
    • MCFA are gaining popularity for their health benefits, offering lower calories, increased satiety, improved gut health, and reduced appetite.

    High Energy Bonds

    • High energy bonds are represented by the symbol "~" and are essential for energy storage and transfer in biological processes, such as metabolic processes.
    • ATP (adenosine triphosphate) is the primary energy currency in the body, containing high-energy bonds between its phosphate groups.
    • Sulfer compounds, including Acetyl CoA, Succinyl CoA, acyl CoA, and HMG CoA, are involved in metabolic reactions.

    Non-Covalent Bonds

    • Non-covalent bonds are reversible interactions crucial for molecular interactions in biological systems.
    • Ionic bonds involve the transfer of electrons, resulting in the formation of positive and negative ions. These bonds are commonly found in salts and are crucial for protein folding and enzyme catalysis.
    • Hydrogen bonds occur through electrostatic attraction between a hydrogen atom and an electronegative atom with a lone pair of electrons. They play a vital role in maintaining the structure and properties of molecules such as DNA and proteins.
    • Electrostatic interactions occur between charged atoms and can be either attractive or repulsive. They play a role in protein structure, particularly in shaping the three-dimensional structure.

    Enzyme Properties & Importance

    • Enzymes are protein catalysts that accelerate chemical reactions in biological systems without being consumed themselves.
    • Essential for life, enzymes lower the energy barrier of reactions, allowing them to occur at physiological temperatures and pH.
    • Simple enzymes consist only of protein molecules.
    • Holoenzymes consist of a protein component (apoenzyme) and a non-protein component (either an organic coenzyme or an inorganic cofactor).
    • Isoenzymes are variants of the same enzyme with similar catalytic activity but different physical and chemical properties, which can be useful for diagnostic purposes.
    • Rate-limiting step is the slowest step in a reaction sequence, which determines the overall rate of the reaction.

    Factors Affecting Rate of Reactions

    • Temperature affects enzyme activity, with an optimal temperature (typically around 37°C for human enzymes). Increased temperatures can lead to enzyme denaturation and loss of activity.
    • pH also influences enzyme activity. Each enzyme has an optimal pH at which it functions best. Variations in pH can affect enzyme activity by altering the ionization state of amino acid residues in the active site.

    Amino Acids: General Structure & Classification

    • Most amino acids have a central carbon atom (α-carbon) bonded to:
      • A hydrogen atom
      • An amino group (NH3+)
      • A carboxyl group (COO-)
      • An R group (side chain) which distinguishes each amino acid chemically
    • Unique groups in side chains of some amino acids:
      • Sulfur group: Methionine and cysteine
      • Hydroxyl group: Serine, threonine, and tyrosine
      • Imino group (NH instead of NH2): Proline
    • Amino acid classification:
      • Structure: Aliphatic (open carbon-hydrogen chain) or aromatic (contains benzene ring)
      • Charge: Neutral (no charge), acidic (donate hydrogen/proton, negative charge at physiologic pH), basic (accept protons/hydrogen, positive charge at physiologic pH)
      • Biological importance: Essential (must be obtained from diet), non-essential (synthesized in the body), semi-essential (histidine and arginine: synthesized in sufficient amounts but require dietary supplementation in specific situations like growth, pregnancy, chronic diseases)
      • Polarity:
        • Non-polar (hydrophobic, always neutral)
        • Polar (hydrophilic, can be neutral, acidic or basic)

    Significance of Nonpolar Amino Acids

    • Nonpolar amino acids tend to cluster together in the interior of proteins found in aqueous solutions (hydrophobic effect). This contributes to the protein's 3D shape.

    Zwitterion

    • Zwitterion: Dipolar ion of an amino acid at its isoelectric point (IEP) in an aqueous medium.

    Clinical Implications of Amino Acids

    • Tyrosine deficiency can lead to hair loss and skin color changes, as it is a precursor for thyroid hormone, adrenaline, nor-adrenaline, and melanin.
    • Glutamine deficiency can cause convulsions, as it is a precursor for GABA (neurotransmitter).
    • Hydroxy-containing amino acids play a role in signal transduction.
    • Certain amino acids (e.g., sulfur-containing) have been linked to obesity.
    • Branched-chain amino acids (valine, leucine, isoleucine) intake is beneficial for patients with liver diseases and bodybuilders.
    • Excessive intake of over-the-counter amino acids can overload the kidneys and lead to kidney failure.

    Proteins in Disease

    • Inborn errors of amino acid metabolism can lead to conditions like mental retardation and blindness.
    • Defects in the globin protein of hemoglobin can cause various problems, from hemolysis (red blood cell breakdown) to impaired oxygen delivery.
    • Immunoglobulin deficiency increases susceptibility to infections and can be fatal.
    • Enzyme defects can lead to serious diseases, such as glycogen storage diseases.
    • Structural protein defects (e.g., collagen) can cause skeletal deformities.
    • Hormone production defects can lead to diseases like diabetes mellitus (insulin deficiency).
    • Abnormal protein deposition can cause diseases like Alzheimer's disease.
    • Coagulation factor deficiency can lead to uncontrolled bleeding.

    Chemical Bonds: Overview

    • Chemical bonds are links or forces between neighboring atoms within a molecule or compound.
    • Strong bonds form molecules and crystals, and their breaking releases energy to drive metabolic processes.
    • High energy bonds are represented by the symbol "~".

    Examples of High Energy Compounds

    • Phosphate compounds: ATP, ADP, GTP, GDP, UTP, UDP, UDP-glucose, creatine phosphate, arginine phosphate, 1,3-bisphosphoglycerate, phosphoenol pyruvate, carbamoyl phosphate.
      • ATP, the main energy currency in the body, contains high energy bonds (phosphoric anhydride bonds) between each phosphate group.
      • ATP is the main energy currency of the body.
    • Sulfur compounds: Acetyl CoA, Succinyl CoA, acyl CoA, HMG CoA

    Non-Covalent Bonds

    • Non-covalent bonds are reversible and crucial for molecular interactions. These include:
      • Ionic bonds
      • Electrostatic interactions
      • Hydrogen bonding

    Ionic Bonds

    • Ionic bonds involve the transfer of an electron, resulting in an anion (negative charge) and a cation (positive charge).
    • Opposing charges attract, forming a molecule.
    • Commonly found in dry forms like salts and throughout the body.
    • Ionic compounds are generally water-soluble.

    Biomedical Importance of Ionic Bonds

    • Protein Folding: Ionic bonds contribute to tertiary and quaternary protein structures.
    • Enzyme Catalysis: Ionic bonds are involved in enzyme catalytic reactions.

    Hydrogen Bonds

    • Hydrogen bonds involve electrostatic attraction between a hydrogen atom and an atom with a lone pair of electrons. The hydrogen must be bonded to an electronegative atom.
    • Weaker than covalent bonds.

    Biomedical Importance of Hydrogen Bonds

    • Structure and Properties of Molecules: Essential for the structure and properties of many molecules, such as the DNA bases adenine-thymine and guanine-cytosine.
    • DNA Replication: Breaking of hydrogen bonds is necessary for DNA replication.
    • Protein Folding: Hydrogen bonding also plays a role in protein folding.

    Electrostatic Interactions

    • Electrostatic interactions occur between positively and negatively charged atoms, leading to attraction or repulsion.
    • The electric charge of an atom determines the strength of the interaction.

    Biomedical Importance of Electrostatic Interactions

    • 3D Protein Structure: Electrostatic interactions contribute to the formation of the 3D structure of proteins.

    Carbohydrates

    • Carbohydrates are composed of carbon, hydrogen, and oxygen in a 2:1 ratio of hydrogen to oxygen.
    • The general molecular formula is (CH2O)n, where n > 3.
    • The three major classes of carbohydrates are monosaccharides, oligosaccharides, and polysaccharides.
    • Monosaccharides are simple sugars, classified by the number of carbon atoms they contain.
    • The most abundant monosaccharides are hexoses (6-carbon sugars), such as glucose and fructose.
    • Monosaccharides contain either an aldehyde group (aldoses) or a keto group (ketoses).
    • The carbonyl group is formed by the carbon atom double-bonded to an oxygen atom.
    • Monosaccharides have asymmetric carbon atoms, allowing for isomerism.
    • Fructose, glucose, and galactose are isomers with the same chemical formula (C6H12O6) but different structures.
    • Oligosaccharides are composed of 2-10 monosaccharide units, with disaccharides being the most abundant.
    • Maltose (malt sugar), lactose (milk sugar), and sucrose (cane sugar) are common disaccharides.
    • Maltose is formed by the hydrolysis of starch and consists of two glucose molecules.
    • Lactose is composed of glucose and galactose and found exclusively in mammalian milk.
    • Lactose intolerance is a condition where individuals cannot fully digest lactose, leading to digestive issues.
    • Sucrose is composed of glucose and fructose and is the most common sugar consumed.

    Lipids

    • Lipids are a heterogeneous group of organic compounds related to fatty acids, containing carbon, hydrogen, and oxygen.
    • They can also contain phosphorus, nitrogen, and sulfur.
    • Lipids are insoluble in water but soluble in nonpolar solvents like ether, chloroform, and acetone.
    • Simple lipids are esters of fatty acids with different alcohols.
    • True fats are esters of fatty acids with glycerol.
    • Monoacylglycerol, diacylglycerol, and triacylglycerol (triglycerides) are formed when glycerol is attached to one, two, or three fatty acids, respectively.
    • Waxes are esters of fatty acids with high molecular weight alcohols.
    • Complex lipids are esters of fatty acids and alcohols with additional head groups.
    • Phospholipids are important components of cell membranes.
    • Glycolipids contain fatty acids, sphingosine, and carbohydrate residues.
    • Other complex lipids include sulfolipids, amino lipids, and lipoproteins.
    • Derived lipids are products of the hydrolysis of simple and complex lipids, such as fatty acids, glycerol, cholesterol, and fat-soluble vitamins.
    • Fatty acids have a long carbon chain with a carboxyl group at one end.
    • The carboxyl group ionizes, forming an anionic group that gives the fatty acid amphipathic nature.
    • Lipids serve as signaling molecules, aid in the solubilization and transport of fat-soluble vitamins, and contribute to energy storage.
    • Disruption of lipid levels is linked to obesity, diabetes, atherosclerosis, hypertension, and abnormalities in fat-soluble vitamin transport.

    Proteins

    • Proteins are the most abundant and diverse molecules in living systems.
    • They play crucial roles in various bodily functions, including metabolism, movement, structural support, transport, immunity, and growth.
    • Amino acids are the building blocks of proteins, characterized by an amino group (NH2) and a carboxylic group (COOH).
    • There are 20 naturally occurring amino acids used to form proteins.
    • Amino acids are linked together by peptide bonds, formed between the carboxyl group of one amino acid and the amino group of another.
    • Peptide bonds are strong covalent bonds, responsible for the primary structure of a protein.
    • Denaturation of proteins does not involve breaking peptide bonds.
    • Ester bonds are formed between the hydroxyl group of an alcohol and the hydroxyl group of a carboxylic acid.
    • Esterification is involved in the formation of triacylglycerols, neurotransmitters like acetylcholine, and some drugs.
    • Ester bonds are broken down by esterase enzymes, such as acetylcholinesterase.
    • Enzyme inhibition is a critical mechanism in drug therapy, exemplified by non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, which inhibit cyclooxygenase (COX) enzymes.

    Factors Affecting Rate of Reactions

    • Several factors impact enzyme activity, influencing the rate of reactions catalyzed by enzymes.
    • Temperature significantly affects enzyme activity:
      • As temperature increases, reaction velocity rises until a peak velocity is reached at the optimum temperature.
      • Beyond the optimum temperature, enzyme activity declines due to denaturation.
      • Fever and hypothermia can be dangerous due to their impact on enzyme function.
    • pH also plays a crucial role in enzyme activity:
      • The concentration of protons (H+) affects the ionization state of both the enzyme and substrate, influencing their interaction.
      • Optimal pH varies depending on the enzyme and reflects the pH of its typical environment in the body.
      • For example, pepsin, a stomach enzyme, is most active at a pH of 1-2, corresponding to the acidic environment of the stomach.

    Fatty Acid Structure

    • Long chain fatty acids (LCFA) are highly water insoluble and require protein association for circulation
    • Saturated fatty acids contain no double bonds, while unsaturated fatty acids contain one or more double bonds
    • Cis double bonds are found naturally in food sources and are associated with health benefits
    • Trans double bonds are typically found in processed foods and linked to increased risk of atherosclerosis
    • Cis double bonds cause a bend or kink in the fatty acid chain due to functional groups being on the same side
    • Trans double bonds have functional groups on opposite sides, resulting in a straighter chain
    • Increased chain length correlates with increased melting temperature (Tm)
    • Adding double bonds decreases the melting temperature (Tm)
    • Membrane lipids commonly contain LCFA, with double bonds helping maintain fluidity

    Fatty Acid Chain Length

    • Short chain fatty acids (SCFA) contain 2-6 carbon atoms
    • SCFA are produced by the body through consumption of high fiber foods like fruits, vegetables, legumes, and whole grains
    • Medium chain fatty acids (MCFA) contain 7-12 carbon atoms
    • MCFA are prevalent in coconut oil and dairy products
    • Despite lower calorie content compared to LCFA, MCFA contribute to higher satiety and reduced appetite
    • MCFA promote gut health by killing harmful bacteria, preventing diarrhea and bloating

    Lipids as Signaling Molecules

    • Lipids play a role in cellular response pathways
    • They aid in solubilizing and transporting fat-soluble vitamins
    • Disruptions in lipid levels, whether from increased dietary intake or metabolic abnormalities, can lead to diseases such as obesity, diabetes, atherosclerosis, hypertension, and abnormalities in the transport of fat-soluble vitamins
    • Obesity - Occurs when there is excess adipose tissue, which is the main storage site for lipids
    • Diabetes - In this disease, the body either does not produce enough insulin or cannot properly use it which impacts the regulation of blood sugar levels, metabolism of lipids
    • Atherosclerosis - Is a build-up of plaque, comprising of lipids, cholesterol, and cellular debris, within artery walls, leading to narrowed arteries and an increased risk of heart attack or stroke
    • Hypertension - is high blood pressure and can be linked to high fat intake
    • Fat-soluble vitamin deficiency - Fat-soluble vitamins (A, D, E and K) are transported to the cells in lipoproteins and an imbalance in lipid metabolism could lead to deficiencies

    Proteins

    • Proteins are the most abundant and functionally diverse molecules in living systems
    • They have numerous critical roles in the body, including:
      • Enzymes and polypeptide hormones regulate metabolism
      • Contractile proteins in muscles enable movement
      • Collagen provides structural support in bones and forms the framework for calcium phosphate crystal deposition
      • Collagen, elastin, and keratin are essential for the structure of skin, hair, and nails
      • Hemoglobin and albumin transport vital molecules in the bloodstream
      • Immunoglobulins defend against infections
      • Coagulation factors regulate bleeding
    • Proteins are essential for growth and development
    • They act as secondary messengers in cell signaling

    Building Blocks of Proteins

    • Amino acids (a.a) are the building blocks of proteins
    • Amino acids contain a carboxylic group (COOH) and an amino group (NH2)
    • The amino group is typically attached to the α-carbon atom adjacent to the carboxyl group
    • Amino acids are linked together via peptide bonds formed between their carboxylic and amino groups
    • There are 20 naturally occurring amino acids used by cells to synthesize proteins

    Polarity of Amino Acids

    • The side chains (R groups) of amino acids can be polar or nonpolar
    • Polar side chains participate in hydrogen bond formation, contributing to protein structure stability
    • The side chain of cysteine contains a sulfhydryl group (-SH), crucial for enzyme activity and disulfide bond formation
    • The nonpolar side chains are found on the exterior of proteins located in hydrophobic environments like membranes
    • The distribution of polar and nonpolar amino acids influences protein folding and function

    Clinical Implications of Amino Acid Changes

    • Sickle cell anemia is caused by a substitution of nonpolar valine for polar glutamate at the sixth position in the β-subunit of hemoglobin A.
    • This change alters the red blood cell shape, making them sickle-shaped, leading to blood vessel blockage and painful episodes

    Amphoteric Property of Amino Acids

    • Amino acids contain both acidic (-COOH) and basic (-NH2) groups
    • They can act as acids and bases in solution, due to the presence of these groups
    • At their isoelectric point (IEP) or pI, amino acids are electrically neutral, carrying equal positive and negative charges
    • The amphoteric nature of amino acids allows plasma proteins to form a buffer system, playing a vital role in maintaining blood pH
    • Buffer systems help to maintain the pH of the blood within a narrow range. They do this by neutralizing acids and bases, preventing large changes in pH.

    Formation of Chemical Bonds

    • Chemical bonds are formed to achieve a stable (lowest-energy) state for atoms
    • Atoms aim to fill their valence shell or satisfy the octet rule by having eight valence electrons
    • Atoms achieve this stability through gaining, losing, or sharing electrons

    Classification of Bonds

    • Bonds can be classified as covalent or non-covalent
    • Covalent bonds are stronger due to the sharing of electrons between adjacent atoms
    • Non-covalent bonds are weaker than covalent bonds and involve interactions between atoms without electron sharing

    Covalent Bonds

    • Covalent bonds are the strongest type of bond
    • Share electrons between adjacent atoms
    • Double or triple bonds form when more than one pair of electrons is shared
    • Covalent bonds can be polar or nonpolar

    Polar Covalent Bonds

    • Occur between atoms with different electronegativity
    • Electrons are shared but spend more time around the more electronegative atom

    Nonpolar Covalent Bonds

    • Form between atoms of the same element or different elements sharing electrons equally

    Covalent Bonds of Biomedical Importance

    • Glycosidic bonds join carbohydrate molecules to other molecules (carbohydrate or other types)
    • Peptide bonds link amino acids together to form proteins
    • Ester bonds connect fatty acids to glycerol in triglycerides and phospholipids

    Non-covalent Bonds

    • Hydrogen bonds form between polar molecules, such as water
    • Ionic bonds occur due to electrostatic attraction between oppositely charged ions
    • Hydrophobic interactions involve repulsion of nonpolar molecules by water
    • Van der Waals forces are weak, short-range forces arising from transient fluctuations in electron distribution
    • The formation of these bonds is dynamic and can be influenced by factors like pH, temperature, and the presence of other molecules
    • Non-covalent bonds play crucial roles in many biological processes, including protein folding, enzyme activity, and DNA structure
    • They are essential for maintaining the three-dimensional structures of biological molecules and interactions between them

    Enzyme Activity

    • Enzymes are biological catalysts that accelerate chemical reactions without being consumed in the process
    • They have a specific three-dimensional structure, with a unique active site where the substrate binds
    • The active site is a region on the enzyme that fits a specific substrate like a lock fits a key
    • Enzyme activity can be influenced by a variety of factors, including:
      • Substrate concentration
      • Enzyme concentration
      • Product concentration
      • Temperature
      • pH
      • The presence of inhibitors or activators

    Effects of Substrate Concentration on Enzyme Activity

    • At low substrate concentrations, the enzyme activity is directly proportional to the substrate concentration
    • This relationship is described as "First-order kinetics"
    • At high substrate concentrations, the enzyme becomes saturated with substrate, limiting enzyme activity
    • The reaction rate reaches a plateau, with a maximum velocity (Vmax)
    • This relationship is described as "zero-order kinetics"

    Effects of Enzyme Concentration on Enzyme Activity

    • Enzyme activity is directly proportional to enzyme concentration until all substrate is bound and a maximum rate is reached
    • Increasing enzyme concentration beyond the maximum rate does not result in a further increase in the reaction rate

    Effects of Product Concentration on Enzyme Activity

    • As product accumulates, enzyme activity decreases due to:
      • Changes in pH of the medium
      • Competition between substrate and product for binding to the active site
      • Binding of product to an allosteric site, potentially altering enzyme activity
    • Allosteric enzymes have other sites (allosteric sites) that have a regulatory function. Binding of a molecule to the allosteric site can affect the shape of the active site
    • Allosteric regulation can either increase or decrease the activity of the enzyme

    Regulation of Enzyme Activity

    • Enzyme activity can be regulated through various mechanisms:
      • Zymogen activation
      • Allosteric regulation
      • Covalent modification
      • Feedback inhibition
      • Enzyme induction and repression

    Zymogen Activation

    • Some enzymes are secreted in an inactive form called zymogens or proenzymes
    • These zymogens are activated at their site of action by specific proteolytic cleavage events
    • Examples include pepsinogen (activated to pepsin), trypsinogen (activated to trypsin), and plasminogen (activated to plasmin)
    • Once activated, enzymes cannot be converted back to their proenzyme form. This irreversible activation serves as a control mechanism for enzyme activity

    Zymogen Activation and Digestive Enzymes:

    • Zymogen activation is vital in the regulation of protein digestion in the gut
    • Pepsinogen is activated to pepsin by the acidic environment of the stomach, hydrolyzing proteins into smaller peptides
    • Trypsinogen is activated to trypsin by enterokinase, which is an enzyme found in the duodenum. Trypsin then activates other digestive enzymes, such as chymotrypsin and carboxypeptidase
    • This cascade of activation ensures that digestive processes are tightly controlled and occur only when needed

    Carbohydrates

    • Carbohydrates are hydrates of carbon, containing hydrogen and oxygen in a 2:1 ratio.
    • The general molecular formula for carbohydrates is (CH2O)n, where n > 3.
    • The three major classes of carbohydrates are monosaccharides, oligosaccharides, and polysaccharides.

    Monosaccharides

    • Monosaccharides are simple sugars.
    • They are classified based on the number of carbon atoms: trioses (C3), tetroses (C4), pentoses (C5), hexoses (C6), heptoses (C7).
    • The 6-carbon sugars, like glucose and fructose, are the most abundant in nature.
    • Monosaccharides contain either an aldehyde group (aldoses) or a keto group (ketoses).
    • They have asymmetric carbon atoms, which allow for isomerism.
    • Isomers are compounds with the same chemical formula but different structures.

    Oligosaccharides

    • Oligosaccharides consist of 2-10 monosaccharide units.
    • Disaccharides are the most abundant oligosaccharides.
    • Examples of disaccharides include:
      • Maltose (malt sugar): major degradative product of starch, hydrolyzes into two glucose molecules.
      • Lactose (milk sugar): composed of glucose and galactose, found in mammals' milk.
      • Sucrose (cane sugar): composed of glucose and fructose.

    Lactose Intolerance

    • Some individuals cannot fully digest lactose, leading to lactose intolerance.
    • Symptoms include diarrhea, gas, and bloating after consuming dairy products.
    • Lactose-free dairy products are available for individuals with this condition.

    Factors Affecting Enzyme Activity

    • Temperature affects enzyme activity, with optimal activity at 37°C for most human enzymes.
    • Increasing temperature increases reaction velocity up to a peak, after which denaturation occurs.
    • pH also influences enzyme activity, as specific chemical groups require certain ionization states for optimal function.
    • Each enzyme has an optimal pH, which is the pH at which it exhibits maximal activity. For example, pepsin's optimal pH is 1-2, reflecting the stomach's environment.

    ### Long Chain Fatty Acids

    • Contain more than 12 carbon atoms, with palmitic acid (16 carbons) serving as an example.
    • Represent the majority of fatty acids in animal tissues and most animal diets
    • In humans, fatty acids with an even number of carbon atoms (16, 18, or 20) are most prevalent, while longer fatty acids (>22 carbons) are found in the brain.

    Rancidity

    • Occurs when lipids are exposed to light, heat, moisture and bacterial action, transforming them into rancid fat.
    • Rancid fat develops unpleasant odour and taste, and becomes acidic.
    • Results from hydrolysis of fat, leading to the release of short-chain volatile fatty acids with unpleasant odours (hydrolytic rancidity).
    • Additionally, oxidation of unsaturated fatty acids occurs, creating peroxides, aldehydes, and ketones (oxidative rancidity).
    • Can be inhibited by adding antioxidants, such as vitamins A and E, and by storing fat in clean, cold environments away from light and moisture.

    Fatty Acid Numbering

    • Two systems exist for numbering carbon atoms in a fatty acid.

    Essential Fatty Acids (EFA)

    • Lipids can either be obtained from the diet or synthesised de novo.
    • The concentration of essential fatty acids varies significantly between individuals.
    • Essential fatty acids that must be obtained from the diet include:
      • Linoleic acid, the precursor of ω-6 fatty acids (possess a terminal double bond six bonds from the ω end).
      • α-linolenic acid, the precursor of ω-3 fatty acids (possess a terminal double bond three bonds from the ω end).
    • Both ω-6 and ω-3 fatty acids are crucial for growth and development.
    • ω-3 fatty acids are found in salmon, sardines, and flaxseeds, whereas ω-6 fatty acids are found in walnuts, peanuts, corn, and sunflower oils.
    • Essential fatty acid deficiency primarily affects infants fed diets deficient in EFAs.
    • Symptoms can include hair loss, low platelet count, and intellectual disability.
    • Dietary replenishment of EFAs reverses the deficiency.

    Lipids in Health and Disease

    • Lipids play essential roles in various bodily functions:
      • Serving as structural elements in biological membranes.
      • Storing and supplying energy, with 1 gram of dietary lipids providing about 9 calories, more than double the energy provided by carbohydrates.
      • Acting as signaling molecules in cellular response pathways.
      • Aiding in the solubilization and transport of fat-soluble vitamins.
    • Disruptions in lipid levels, whether due to increased dietary intake or abnormal metabolism, are linked to numerous diseases, including:
      • Obesity.
      • Diabetes.
      • Atherosclerosis.
      • Hypertension.
      • Abnormalities in fat-soluble vitamins and lipid transport in blood.

    What are Proteins?

    • Proteins are the most abundant and functionally diverse molecules in living organisms.
    • They perform various crucial tasks in the body, including:
      • Enzymes and polypeptide hormones direct and regulate metabolism.
      • Contractile proteins in muscles enable movement.
      • Collagen in bones provides a framework for calcium phosphate crystal deposition.
        • Collagen, elastin, and keratin proteins also play essential roles in the structure of skin, hair, and nails.
      • Proteins like hemoglobin and albumin in the bloodstream transport essential molecules, while immunoglobulins combat infectious bacteria and viruses.
      • They form coagulation factors that control bleeding.
      • Essential for growth and development.
      • Proteins form molecules (secondary messengers) that facilitate signal transmission between and within cells.

    What are the Building Blocks of Proteins?

    • Known as amino acids, they are characterized by the following:
      • An amino acid (a.a.) is an organic acid (contains the carboxylic group COOH), where one hydrogen atom is replaced by an amino group (NH2).
      • The amino group is typically attached to the α-carbon atom next to the -COOH.
      • Amino acids join together through their carboxylic and amino groups via a strong bond called a peptide bond to form proteins.
      • There are 20 naturally occurring amino acids used by cells to build proteins. These are called primary or common amino acids.

    Significance of Polar Amino Acids

    • Polar side groups participate in hydrogen bond formation, which helps stabilize the protein structure.
    • Cysteine, with its (−SH) side chain, is a crucial component of the active site of many enzymes.
    • It also participates in forming disulfide bonds, which further stabilize the protein structure.

    Clinical Implications

    • Sickle cell anemia, a disorder that causes red blood cells to become sickle-shaped, results from the replacement of polar glutamate with nonpolar valine at the sixth position in the β subunit of hemoglobin A. This alteration causes the RBCs to become sticky when oxygen levels are low and can block blood vessels, leading to severe pain episodes.

    Amphoteric Property of Amino Acids

    • The amphoteric property of amino acids means they can act both as acids and bases in solution due to the presence of both an acidic (-COOH) and a basic (-NH2) group.
    • When neutral amino acids fully ionize to form dipolar ions (Zwitterions), they carry both negative and positive charges, which balance out.
    • The pH at which an amino acid carries an equal positive and negative charge (electrically neutral) is called its isoelectric point (IEP) or pI.
    • At its IEP, an amino acid's ions do not migrate towards any electrode when an electric current is applied. This behavior results in precipitation on the spot.
    • Due to their amphoteric property, plasma proteins form an efficient buffer system and play a vital role in maintaining blood pH.

    N.B.

    • Alterations in stomach acidity (e.g., with aging, some medications, and surgeries) can lead to improper functioning of the pepsin enzyme and maldigestion.
    • Other enzymes designed for neutral pH environments can be denatured by such acidic conditions. For instance, salivary amylase, which has an optimum pH of (6-8), becomes inactive upon reaching the stomach.
    • Extreme pH changes can denature enzymes and lead to loss of their function.

    Carbohydrates

    • Fructose is a very sweet sugar often used by diabetics and obese individuals as an alternative to glucose
    • High levels of fructose can increase hunger and sugar cravings
    • Polysaccharides are high molecular weight polymers, commonly found in food
    • Glycogen is a branched polysaccharide, the main storage form of carbohydrate in humans
    • Starch is the plant storage form of carbohydrate and the most abundant carbohydrate in the diet
    • Cellulose is a structural carbohydrate in plants, humans cannot digest it
    • Cellulose provides fiber in the diet, which helps movement of food through the gut

    Carbohydrate Derivatives

    • Deoxy-monosaccharides have a hydrogen atom replacing a hydroxyl group
    • Amino sugars have an amino group replacing a hydroxyl group
    • Sugar acids have a carboxyl group replacing a hydroxyl group

    Amino Acids

    • Most amino acids have a central carbon atom with a hydrogen atom, an amino group, a carboxyl group, and an R group
    • The R group gives each amino acid its unique properties
    • Amino acids can be classified based on their structure, charge, biological importance, and polarity

    Nonpolar Amino Acids

    • Nonpolar amino acids tend to cluster together in the interior of proteins

    Clinical Implications of Amino Acids

    • Tyrosine deficiency can lead to hair loss and skin color changes
    • Glutamine deficiency can cause convulsions
    • Hydroxy-containing amino acids play a role in signal transduction
    • Sulfur-containing amino acids are linked to obesity
    • Intake of branched-chain amino acids may be beneficial for patients suffering from liver diseases

    Proteins in Disease

    • Inborn errors of amino acid metabolism can lead to mental retardation and blindness
    • Defects in globin protein (in hemoglobin) can lead to hemolysis (red blood cell breakdown) and oxygen delivery problems
    • Immunoglobulin deficiencies increase susceptibility to infections
    • Enzyme defects can lead to diseases like glycogen storage diseases
    • Collagen defects can lead to skeletal deformities
    • Hormone production defects can lead to diseases like diabetes mellitus
    • Abnormal protein deposition can lead to diseases like Alzheimer's disease
    • Coagulation factor deficiency can lead to uncontrolled bleeding

    Chemical Bonds

    • Bonds are forces that link neighboring atoms
    • Hydrogen bonds play a vital role in the structure and properties of many molecules
    • Breaking of hydrogen bonds is necessary before DNA replication
    • Hydrogen bonding also plays a role in protein folding
    • Electrostatic interactions occur between positively and negatively charged atoms
    • Electrostatic interaction can be repulsive or attractive
    • Electrostatic interactions play a role in protein folding

    Enzymes

    • Enzymes are protein catalysts that increase the rate of chemical reactions
    • Enzymes lower the activation energy of reactions, making them occur faster
    • Enzymes are not consumed during the reaction
    • Simple enzymes are made up of only protein molecules
    • Holoenzymes are made up of protein and non-protein components
    • Coenzymes are organic non-protein components of holoenzymes
    • Inducers increase the expression of genes that code for enzymes
    • Repressors decrease the expression of genes that code for enzymes
    • Inhibitors decrease the rate of enzyme-catalyzed reactions

    Competitive Inhibition

    • The inhibitor binds to the same site as the substrate
    • The inhibitor is structurally similar to the substrate
    • Competitive inhibition is reversible and can be overcome by increasing substrate concentration
    • Statins are examples of competitive inhibitors used to reduce cholesterol levels

    Non-competitive inhibition

    • The inhibitor binds at a different site from the substrate
    • Non-competitive inhibitors can bind to either the free enzyme or the enzyme-substrate complex
    • Non-competitive inhibition cannot be reversed by increasing substrate concentration
    • Non-competitive inhibitors often have no structural similarity to the substrate
    • Non-competitive inhibitors lower the Vmax of the enzyme but do not affect the Km

    Glucuronic Acid

    • Low levels of glucuronic acid in premature babies make them more susceptible to jaundice due to bilirubin build-up.
    • Severe jaundice, known as kernicterus, can damage the brain leading to mental retardation and vision problems.
    • Liver failure patients are prone to drug toxicity due to decreased glucuronic acid synthesis and inability to detoxify drugs.
    • Sugar alcohols like mannitol (a diuretic) and sorbitol (a laxative and artificial sweetener) have reduced calories compared to regular sugars and can stimulate taste buds.
    • Sorbitol is naturally present in some fruits like cherries.
    • Excess sorbitol consumption can lead to bloating and digestive issues.

    Carbohydrates

    • Carbohydrates are a primary source of dietary calories for most organisms.
    • They act as an energy storage form in the body.
    • Carbohydrates serve as components of cell membranes, facilitating intercellular communication.
    • While 1 gram of carbohydrate provides 4 calories, they are not essential nutrients as the body can obtain energy from proteins and fats.
    • Carbohydrates are readily converted into glucose, the primary energy source for cells.
    • Carbohydrates provide early but short-term satiety compared to proteins and fats.
    • Abnormal glucose metabolism is associated with diseases like diabetes mellitus and certain types of cancers.
    • Inborn errors in carbohydrate metabolism can lead to various abnormalities, including mental retardation and hepatomegaly.

    Lipids

    • Lipids act as signaling molecules involved in cellular response pathways.
    • They aid in solubilizing and transporting fat-soluble vitamins.
    • Disruptions in lipid levels, either through increased dietary intake or abnormal metabolism, are linked to diseases like obesity, diabetes, atherosclerosis, hypertension, and abnormalities in fat-soluble vitamin transport.

    Proteins

    • Proteins are the most abundant and functionally diverse molecules in living systems.
    • They play numerous roles in the body, including:
      • Enzymes and polypeptide hormones regulating metabolism.
      • Contractile proteins in muscles facilitating movement.
      • Collagen, a structural protein in bone, providing a framework for calcium phosphate deposition.
      • Collagen, elastin, and keratin proteins contributing to skin, hair, and nail structure.
      • Hemoglobin and albumin, transport proteins in the bloodstream, carrying vital molecules.
      • Immunoglobulins, fighting infections.
      • Coagulation factors, controlling bleeding.
      • Essential for growth and development.
      • Secondary messengers, transmitting signals between and within cells.

    Amino Acids

    • Amino acids are the building blocks of proteins.
    • They are organic acids with a carboxylic group (COOH) where one hydrogen atom is replaced by an amino group (NH2).
    • The amino group is typically attached to the α-carbon atom next to the -COOH.
    • Amino acids are linked through peptide bonds formed between their carboxylic and amino groups.
    • There are 20 naturally occurring amino acids used by cells to synthesize proteins.
    • Some amino acids are precursors to important compounds. For example:
      • Tyrosine is a precursor to thyroid hormone, adrenaline, nor-adrenaline, and melanin. Deficiencies in tyrosine can cause hair loss and skin discoloration.
      • Glutamine is a precursor to GABA, a neurotransmitter. Severe glutamine deficiency can cause seizures.
      • Hydroxy-containing amino acids play a role in signal transduction.
    • Some amino acids, such as sulfur-containing amino acids, have been linked to obesity.
    • Intake of branched-chain amino acids (valine, leucine, isoleucine) is beneficial for patients with liver diseases and bodybuilders.
    • Excessive over-the-counter amino acid intake can be dangerous, potentially overloading the kidneys and leading to kidney failure.
    • Inborn errors in amino acid metabolism can result in various manifestations, including mental retardation and blindness.
    • Defects in the globin protein of hemoglobin can lead to serious conditions, ranging from red blood cell breakdown (hemolysis) to impaired oxygen delivery to tissues.
    • Immunoglobulin deficiency increases susceptibility to infections, potentially leading to death from minor infections.
    • Enzyme defects can cause serious diseases, such as glycogen storage diseases, leading to liver enlargement and death.
    • Defects in structural proteins like collagen can result in skeletal deformities.
    • Abnormalities in hormone production can lead to diseases like diabetes mellitus (insulin defects).
    • Abnormal protein deposition can contribute to diseases like Alzheimer's disease.
    • Coagulation factor deficiencies causing uncontrolled wound bleeding.

    Chemical Bonds

    • A bond represents a link or force between neighboring atoms in a molecule or compound.
    • Atoms can be connected by strong bonds, forming molecules or crystals.

    Hydrogen Bonds

    • Hydrogen bonds play a crucial role in the structure and properties of many molecules.
    • They are present in DNA, linking nucleotide bases adenine-thymine and guanine-cytosine.
    • Breaking of hydrogen bonds is necessary for DNA replication.
    • Hydrogen bonding is also involved in protein folding.

    Electrostatic Interactions

    • Electrostatic interactions occur between positively and negatively charged atoms, resulting in either attraction or repulsion.
    • The electric charge of an atom determines the extent of electronic interaction with other atoms.
    • Electrostatic interactions contribute to the formation of the 3D structure of proteins.

    Enzymes

    • Enzymes are protein catalysts that accelerate chemical reactions in biological systems.
    • They speed up reactions without being altered or consumed.
    • Many essential reactions in living cells would proceed too slowly without enzymes due to high energy barriers.
    • Enzymes lower these energy barriers, accelerating the rate of reactions.
    • Enzymes prevent unwanted reactions by keeping their energy barriers high.

    Enzyme Types

    • Simple enzymes consist solely of protein molecules.
    • Holo enzymes comprise both protein and non-protein components.
      • The protein component is called the apoenzyme.
      • If the non-protein component is an organic compound, it's called a coenzyme.

    Enzyme Inhibition

    • Enzyme inhibition is a common mechanism in drug therapy.
    • Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen inhibit the cyclooxygenase (COX) enzyme, responsible for pain, fever, and inflammation mediators.
    • NSAIDs are used as analgesics, antipyretics, and anti-inflammatories.

    Factors Affecting Enzyme Activity

    • Several physical and chemical factors influence enzyme activity, including:
      • Temperature
      • pH

    Temperature

    • Reaction velocity increases with temperature until reaching a peak.
    • Most human enzymes have an optimal temperature of 37°C.
    • At 0°C, enzymes are inactive.
    • Between 0° and 40°C, enzyme activity doubles with every 10°C increase in temperature.
    • Further temperature elevation leads to decreased reaction velocity due to enzyme denaturation.
    • Fever and hypothermia can be life-threatening because they affect enzyme function.

    pH

    • The concentration of protons (H+) affects reaction velocity because the catalytic process often requires both enzyme and substrate to have specific chemical groups in either an ionized or unionized state for interaction.
    • For example, catalytic activity may require an amino group of the enzyme to be in the protonated form (-NH3+).
    • Enzymes are typically active in specific pH ranges.
    • The pH at which an enzyme exhibits maximal activity is called the "optimum pH".
    • The optimal pH varies among enzymes and often reflects the natural pH environment in which they function.
    • For example, pepsin, a digestive enzyme in the stomach, has an optimal pH of 1-2, matching the stomach's normal pH.

    Fatty Acids

    • Long chain fatty acids (LCFA) are highly water insoluble and require protein to be transported in circulation.
    • Saturated fatty acids have no double bonds.
    • Unsaturated fatty acids have one or more double bonds (mono- or polyunsaturated).
    • Cis double bonds (functional groups on the same side) are present in natural foods like salmon, nuts, and olive oil.
    • Cis double bonds cause the fatty acid to bend or kink at that position.
    • Trans double bonds (functional groups on opposite sides) are prevalent in artificially produced foods and, along with saturated fatty acids, are linked to an increased risk of atherosclerosis.
    • Most fatty acids in humans are saturated or monounsaturated.
    • Increasing the chain length of fatty acids increases their melting temperature (Tm).
    • The presence of double bonds in some fatty acids helps maintain the fluidity of lipids, particularly in membrane lipids which typically contain LCFA.
    • Short chain fatty acids (SCFA) contain 2 to 6 carbon atoms, produced by the body when digesting high-fiber foods like fruits, vegetables, legumes, and whole grains.
    • Medium chain fatty acids (MCFA) contain 7 to 12 carbon atoms.
    • MCFA are found in coconut oil and dairy products.
    • MCFA offer potential health benefits: reduced calories compared to LCFA, increased satiety, reduced appetite, and improved gut health by killing harmful bacteria without affecting good bacteria.
    • Long chain fatty acids (LCFA) contain more than 12 carbon atoms.
    • LCFA are the most abundant fatty acids in animal tissues and diets.
    • In humans, fatty acids with an even number of carbon atoms (16, 18, or 20) predominate, with longer fatty acids (>22 carbons) found in the brain.

    Rancidity

    • Exposure to light, heat, moisture, and bacterial action can cause lipids to become rancid fat.
    • The characteristics of rancid fat include bad odor, taste, and an acidic reaction.
    • Rancidity results from slight hydrolysis of fat, leading to the release of short-chain fatty acids with a foul odor (hydrolytic rancidity).
    • Simultaneous oxidation of unsaturated fatty acids forms peroxides, aldehydes, and ketones (oxidative rancidity).
    • Rancidity can be prevented by adding antioxidants like Vitamin A and E and storing fat in a clean, cold, and dark place away from moisture.

    Essential Fatty Acids (EFA)

    • Essential fatty acids must be obtained from the diet.
    • Linoleic acid is the precursor of ω-6 fatty acids, which have a terminal double bond six bonds from the ω end.
    • α-linolenic acid is the precursor of ω-3 fatty acids, with a terminal double bond three bonds from the ω end.
    • Both ω-6 and ω-3 fatty acids are required for growth and development.
    • ω-3 fatty acids are found in salmon, sardines, and flaxseeds, while ω-6 fatty acids are found in walnuts, peanuts, corn, and sunflower oils.
    • Essential fatty acid deficiency, more common in infants, can lead to hair loss, low platelets, and intellectual disability.
    • Dietary replenishment of EFA can reverse deficiency.

    Lipids and Health

    • Lipids play various crucial roles in the body:
      • Structural elements in biological membranes
      • Energy storage and supply
      • 1 gram of dietary lipids provides about 9 Calories, more than double the energy provided by carbohydrates.

    Hydrogen Bonds

    • Play a pivotal role in the structure and properties of many molecules, including:
      • DNA, where they form between nucleotide bases adenine–thymine (2 hydrogen bonds) and guanine–cytosine (3 hydrogen bonds).
      • Protein folding.

    Electrostatic Interactions

    • Electrostatic interactions occur between atoms with opposite charges.
    • They contribute to the 3D structure of proteins.

    Enzymes

    • Enzymes are protein catalysts in biological systems that accelerate chemical reactions without being consumed or altered.
    • Enzymes are essential for life, allowing reactions to occur at a pace compatible with life processes.
    • Cellular reactions have high energy barriers, requiring enzymes to lower the barrier and increase the rate of reaction.
    • Enzymes are classified into:
      • Simple enzymes: Made of only protein molecules.
      • Holo enzymes: Consist of protein groups and non-protein components.
        • The protein component is called an apoenzyme.
        • The non-protein organic component is called a coenzyme.
        • The non-protein inorganic component is called a cofactor.

    Isoenzymes (Isozymes)

    • Enzymes with similar catalytic activity, acting on the same substrate to produce the same product, but originating from different sites and exhibiting distinct physical and chemical properties (e.g., amino acid composition and immunological behavior).
    • LDH (Lactate dehydrogenase) is an example of an isoenzyme that exists in five forms, each with four polypeptide chains.

    Rate Limiting Steps

    • The slowest step in any reaction, which sets the pace for the entire reaction.
    • Typically occurs early in the pathway.

    Enzyme Properties

    • Active site: A special pocket or cleft on enzyme molecules where the substrate binds.
    • The active site is formed by protein folding and contains amino acid side chains involved in substrate binding and catalysis.
    • The substrate binds to the enzyme non-covalently, forming an enzyme-substrate (ES) complex.
    • The ES complex is converted into an enzyme-product (EP) complex, which then dissociates into enzyme and product.
    • The "induced-fit model" describes the flexibility of the binding and active sites, adapting to the substrate's shape during binding.

    Enzyme Inhibition

    • Process that slows down or stops enzyme activity.

    Factors Affecting the Rate of Reactions

    • Various physical and chemical factors influence enzyme activity:

    Temperature

    • Reaction velocity increases with temperature up to a peak velocity (optimum temperature).
    • The optimum temperature for most human enzymes is 37°C.
    • At zero °C, enzymes are inactive.
    • Temperature increases of 10°C between 0° and 40°C double the enzyme activity.
    • Temperatures exceeding the optimum lead to a decrease in reaction velocity due to denaturation of the enzyme.

    pH

    • The concentration of protons (H+) affects reaction velocity.
    • Catalytic processes often require specific chemical groups on enzymes and substrates to be in either ionized or unionized states for interaction.
    • Different enzymes have different optimum pH levels, reflecting the pH at which they normally function in the body.
    • For example, pepsin, a stomach enzyme, is most active at pH 1-2, the normal pH of the stomach.

    Lipids

    • Are a heterogeneous group of organic compounds related to fatty acids that contain C, H, and O
    • Can also contain P, N, and S.
    • Are insoluble in water but soluble in nonpolar solvents like ether, chloroform, benzene, and acetone
    • Are classified into simple lipids, complex lipids, and derived lipids

    Simple Lipids

    • Are esters of fatty acids with different alcohols
    • True Fats:
      • Esters of fatty acids with glycerol.
      • Monoacylglycerol: Glycerol attached to 1 fatty acid
      • Diacylglycerol: Glycerol attached to 2 fatty acids
      • Triacylglycerol (Triglycerides): Glycerol attached to 3 fatty acids. The 3 fatty acids linked to the glycerol are usually different.
    • Waxes: Esters of fatty acids with high molecular weight alcohols

    Complex Lipids

    • Are esters of fatty acids and alcohols with some other head groups.
    • Phospholipids: (see Lipid Structure & functions in bio-membranes)
    • Glycolipids: Lipids containing fatty acid, sphingosine, and carbohydrate residues.
    • Others: Include sulfolipids, amino lipids, and lipoproteins, which are modified forms of lipids.

    Derived Lipids

    • Include the hydrolytic products of the simple and complex lipids.
    • Examples: Fatty acids, glycerol, cholesterol, Fat soluble vitamins: Vitamins A, D, E, and K.

    Properties of Fatty Acids

    • Molecules consisting of carbon, hydrogen, and oxygen, principally linked by non-polar carbon–hydrogen (C–H) bonds forming chain with a carboxyl group at one end.
    • The terminal carboxyl group (–COOH) ionizes, becoming –COO−. This anionic group has an affinity for water, giving the fatty acid its amphipathic nature (having both a hydrophilic and a hydrophobic region).

    Amino Acids

    • Are the building blocks of proteins.
    • Most amino acids have a central carbon atom (α-carbon) to which is attached a hydrogen atom, an α-amino group,( NH3 +), α-carboxyl group,( COO–.), and R group (side chain)
    • The side chain or R group distinguishes each amino acid chemically.
    • Some amino acids have unique groups in their side chains, for example:
      • Sulfur group: in methionine and cysteine
      • Hydroxyl group: in serine, threonine and tyrosine
      • Imino group (NH instead of NH2): in proline

    Classification of Amino Acids

    • According to structure: amino acids can be aliphatic (open chain of carbon and hydrogen) or aromatic (contain benzene ring)
    • According to charge: amino acids can be neutral (carry no charges), acidic (can donate hydrogen or proton and carry a negative charge in physiologic pH), or basic (can accept protons or hydrogen, and carry a positive charge in physiologic pH)
    • According to biological importance: amino acids can be essential (have to be taken in diet), non-essential (can be synthesized in our bodies), or semi-essential (histidine and arginine ) which are synthesized in sufficient amounts in our body, but if their requirements increase such as in periods of growth, pregnancy, after surgeries and in chronic diseases such as liver and kidney diseases, they have to be taken in diet.
    • According to polarity: Which is the ability of the amino acid side chain to gain or lose protons or participate in hydrogen or ionic bonds, amino acids can be non-polar (hydrophobic and always neutral) and polar (hydrophilic, can be neutral, acidic and basic)

    Significance of Nonpolar Amino Acids

    • In proteins found in aqueous solutions (a polar environment), the side chains of the nonpolar amino acids (acting as hydrophobic) tend to cluster together in the interior of the protein where they are away from water. This phenomenon, known as the hydrophobic effect, helps give the protein its three-dimensional shape.

    Enzymes

    • Are biological catalysts usually proteins that increase the rate of a reaction without being consumed in the reaction, they also lower the activation energy.
    • Have high specificity and are commonly named after the reactions they catalyze or their substrates.
    • Examples: - Kinases (add phosphate groups) - Dehydrogenases (remove hydrogen atoms) - Hydrolases (break bonds using water) - Ligases (join molecules) - Isomerases (rearrange atoms within a molecule)
    • Enzymes are made of two parts:
      • Apoenzyme: The protein part
      • Cofactor: The non-protein component. If the non-protein component is an inorganic group it is called a cofactor (Fe 2+, Mn 2+, or Zn 2+ ions). If the non-protein part is bound so tightly to the apoenzyme and is difficult to remove without damaging the enzyme it is sometimes called a prosthetic group.
    • Holoenzyme is a complete, catalytically active enzyme containing both apoenzyme and cofactor.

    Important Enzyme Definitions

    • Isoenzymes (Isozymes): These are enzymes having similar catalytic activity, act on the same substrate and produce the same product but originated at different site and exhibiting different physical and chemical characteristics such as amino acid composition and immunological behavior. Example: LDH (Lactate dehydrogenase) exists in five different forms each having four polypeptide chains. H= Heart and M=Muscle.LDH-1 H H H H LDH-2 H H H M LDH-3 H H M M LDH-4 H M M M LDH-5 M M M M
    • Rate Limiting Steps: The rate limiting step in any reaction is its slowest step. It sets the pace for the entire reaction. It usually occurs early in the pathway.

    Properties of Enzymes

    • Active site: Enzyme molecules contain a special pocket or cleft called the active site. The active site, formed by folding of the protein, contains amino acid side chains that participate in substrate binding and catalysis.
    • Substrate: The molecule or reactant that the enzyme acts upon to form products) binds the enzyme noncovalently, forming an enzyme–substrate (ES) complex, where the substrate attaches itself to the specific active sites on the enzyme molecule by reversible interactions formed by Hydrogen bonds and Hydrophobic interactions.
    • ES complex is then converted to an enzyme–product (EP) complex that subsequently dissociates to enzyme and product.
    • Induced-fit model: The enzyme substrate binding is no longer viewed as the rigid picture of a key lock binding. Instead, a more flexible model of the binding is provided by the “induced-fit model” in which the binding and active sites are not fully pre-shaped. The essential elements of the binding site are present to the extent that the correct substrate can position itself properly.
    • Km: Michaeles-Menten constant. It is a measure of the affinity of the enzyme for its substrate.
    • Vmax: Maximum velocity of the reaction.
    • First order: If the substrate concentration is much less than km, the velocity of the reaction is directly proportionate to substrate concentration. The rate of the reaction is said to be “First order”.
    • Zero order: If the substrate concentration is much greater than Km, the velocity is constant (plateau) and equal to Vmax as all the enzymes are saturated with substrate. The rate of reaction is independent of substrate concentration and said to be “Zero order”.
    • Enzyme Concentration: The rate of the reaction is directly proportional to enzyme concentration provided that the substrate concentration is unlimited until a maximum rate is reached. At this point, any increase in enzyme concentration does not affect the rate of the reaction.
    • Product Concentration: As product accumulates throughout the reaction, the enzyme activity decreases. This may be due to:
      • Change in the pH of the medium.
      • The product is somehow similar to the substrate, so it may compete with it to the catalytic site of the enzyme.
      • The product may bind to the enzyme at the allosteric site (in case of allosteric enzyme).

    Regulation of Enzyme Activity

    • Zymogen activation: Some enzymes are secreted in an inactive form that can be activated when they are required. These are known as “Proenzymes” or “Zymogens”. At the site of action of these enzymes, specific peptide bonds are hydrolysed. Many of the digestive enzymes and enzymes concerned with blood coagulation are in this group e.g. Pepsinogen to pepsin, Trypsinogen to trypsin, plasminogen to plasmin. After hydrolysis when the enzyme is activated, it cannot be reconverted into proenzyme form.
    • Allosteric regulation: Allosteric enzymes have two or more binding sites. The substrate binding site is called catalytic site. Other binding sites are called regulatory or allosteric sites. The binding of the substrate to the catalytic site is affected by the binding of a regulator (activator or inhibitor) to the regulatory site.
    • Feedback Inhibition: The end product of a metabolic pathway acts as an inhibitor for an enzyme catalyzing a reaction early in the pathway.

    Inhibition

    • Competitive Inhibition: The inhibitor competes with the substrate for binding to the active site of the enzyme. Km increases, Vmax remains unchanged. This type of inhibition can be overcome by increasing the concentration of the substrate.
    • Non-Competitive Inhibition: The inhibitor binds to the enzyme at a site other than the active site, but changes the shape of the enzyme so that the substrate can no longer bind. Km remains unchanged, Vmax decreases.
    • Irreversible Inhibition (Enzyme poison): The Inhibitor combines covalently tightly and irreversibly to the functional group of the enzyme destroying it. At any given concentration, the inhibitor will destroy the enzyme permanently, thus it’s called “Enzyme Poison”. This type of inhibition decreases the Vmax while the Km stays the same unchanged. There is no competition between substrate and inhibitor because the inhibitor has no structural resemblance to the substrate.

    Examples of Clinical Implications of Enzyme Inhibition

    • Lead may non-competitively inhibit important enzymes in the heme synthesis pathway leading to anemia. Reducing agents as vitamin C and vitamin E can regain the activity of the enzyme. Routine supplementation of these vitamins is therefore advised for people living or working in areas of high pollution or near factories.
    • Organophosphates found in most pesticides when accidentally ingested or inhaled lead to irreversible inhibition of enzymes controlling nerve signals in the body.
    • Cyanide leads to irreversible inhibition of enzymes responsible for ATP synthesis. Therefore, low doses of cyanide present in cigarettes are responsible for many of smoking side effects.

    Enzymes in Clinical Use:

    • Diagnosis of Diseases:
    • Plasma enzymes can be classified into two major groups:
      • Functional Plasma Enzymes: These are a relatively small group of enzymes secreted into the plasma by certain organs and perform a certain function in the plasma (For example: the liver secretes zymogens involved in blood coagulation cascade).
      • Non-functional plasma enzymes: These are large enzyme species released from cells during normal cell turnover. These enzymes are normally intracellular and have no physiologic function in the plasma. In healthy individuals, the levels of these enzymes are fairly constant and represent a steady state in which the rate of release from cells into the plasma is balanced by an equal rate or removal from the plasma. Many diseases that cause tissue damage result in an increased release of intracellular enzymes into the plasma which correlates with the extent of tissue damage. Thus, the degree of elevation of a particular enzyme in plasma is often useful in evaluating the diagnosis and prognosis for the patient.

    Lipids

    • Lipids are a heterogeneous group of organic compounds related to fatty acids
    • They are relatively insoluble in water, but soluble in nonpolar solvents
    • Lipids are involved in many bodily functions, including energy storage, cell signaling, and the transport of fat-soluble vitamins
    • Disruptions in lipid levels or metabolism can lead to various diseases, including obesity, diabetes, atherosclerosis, and hypertension

    Fatty Acids

    • Composed of carbon, hydrogen, and oxygen, principally linked by non-polar carbon-hydrogen (C-H) bonds
    • Possess a carboxyl group at one end, making them amphipathic
    • They are a major component of lipids, playing a key role in energy storage and cell signaling

    Proteins

    • The most abundant and functionally diverse molecules in living systems
    • Function in various ways within the body, including:
      • Enzymes and polypeptide hormones: Regulate metabolism
      • Contractile proteins: Enable movement
      • Structural proteins: Provide framework for tissues like bone, skin, hair, and nails
      • Transport proteins: Carry essential molecules in the bloodstream
      • Immune proteins: Fight infections
      • Coagulation factors: Control bleeding
      • Signal transduction: Act as secondary messengers within cells

    Amino Acids

    • The building blocks of proteins
    • Contain a carboxylic group (COOH) and an amino group (NH2)
    • The amino group is typically attached to the α-carbon atom next to the -COOH
    • Twenty naturally occurring amino acids are found in the body, known as primary amino acids
    • Amino acids are classified based on:
      • Structure (aliphatic vs aromatic)
      • Charge (neutral, acidic, or basic)
      • Biological importance (essential, non-essential, semi-essential)
      • Polarity (non-polar, or polar)

    Significance of Polar and Nonpolar Amino Acids

    • Nonpolar amino acids:
      • In aqueous solutions, they tend to cluster together within the protein core, avoiding water interactions (hydrophobic effect)
      • In hydrophobic environments (e.g., membranes), they are exposed on the protein surface, interacting with lipids
    • Polar amino acids:
      • Participate in hydrogen bond formation, stabilizing protein structure
      • Cysteine, with its -SH group, is crucial for the active site of many enzymes and forms disulfide bonds that stabilize the protein structure

    Amphoteric Property of Amino Acids

    • Amino acids can act as both acids and bases due to the presence of both carboxyl and amino groups
    • When completely ionized as dipolar ions (zwitterions), they carry equal positive and negative charges
    • The isoelectric point (IEP) is the pH at which an amino acid has no net charge
    • Amphoteric properties allow plasma proteins to contribute to the blood's pH buffer system

    Enzyme Regulation

    • Enzymes are proteins that catalyze biochemical reactions
    • They are subject to various regulatory mechanisms:
      • Zymogen Activation: Protective mechanism that prevents premature activation of enzymes
      • Covalent Modification: Addition or removal of phosphate groups, often to serine or tyrosine residues, can activate or inactivate enzymes
      • Allosteric Modulation: Binding of regulatory molecules (effectors) to allosteric sites (non-active sites) on enzymes, leading to catalytic changes
        • Positive effectors enhance enzyme activity
        • Negative effectors reduce enzyme activity
      • Feedback Inhibition: Allosteric regulation where the final product inhibits the enzyme activity at an earlier step in the metabolic pathway
      • Enzyme Synthesis: Cells can regulate enzyme levels by altering the rate of enzyme synthesis (induction or repression)
        • Induction: Increased synthesis, leading to more enzyme activity
        • Repression: Reduced synthesis, leading to less enzyme activity

    Carbohydrates: Chemical Blocks of Life

    • Carbohydrates are generally hydrates of carbon containing hydrogen and oxygen in a ratio of 2:1, with the general molecular formula (CH2O)n, where n > 3.
    • There are three major classes of carbohydrates: monosaccharides, oligosaccharides, and polysaccharides.
    • Monosaccharides: (simple sugars) are classified based on the number of carbon atoms.
      • The most abundant monosaccharides are the 6-carbon sugars like glucose and fructose.
      • They can be either aldoses (contain an aldehyde group) or ketoses (contain a keto group).
    • Oligosaccharides: disaccharides are the most abundant.
      • Maltose (malt sugar) is the major degradative product of starch, hydrolyzed to two glucose molecules.
      • Lactose is composed of glucose & galactose subunits, found exclusively in milk (milk sugar).
        • It is the least sweet sugar.
        • It is the only source of galactose, essential for neural and immunological processes, including ABO blood types.
        • It helps absorb calcium, copper, and zinc, especially in infancy.
        • Lactose intolerance occurs when individuals cannot fully digest lactose, leading to diarrhea, gas, and bloating after consuming dairy products.
      • Sucrose (cane sugar) is composed of glucose and fructose subunits.
    • Polysaccharides: contain >10 monosaccharide units.

    Lipids: Chemical Blocks of Life

    • Lipids are organic compounds that are insoluble in water but soluble in organic solvents.
    • Lipids play a crucial role in energy storage, insulation, and membrane structure.
    • Fatty Acids: building blocks of many lipids, consist of a long hydrocarbon chain with a carboxylic acid group at one end.
      • Saturated fatty acids have no double bonds.
      • Unsaturated fatty acids have one or more double bonds.
        • Cis double bonds are naturally occurring and cause a bend or kink in the fatty acid chain.
        • Trans double bonds are found in artificially produced foods and are associated with an increased risk of atherosclerosis.
    • Chain length of Fatty Acids: classified into short, medium, and long chain fatty acids based on the number of carbon atoms.
      • Short-chain fatty acids (2-6 carbons) are produced by the human body from high-fiber foods.
      • Medium-chain fatty acids (7-12 carbons) are found in coconut oil and dairy products.
      • Long-chain fatty acids (13+ carbons) are commonly found in animal fats and oils.
    • Other Lipids:
      • Phospholipids are components of cell membranes with both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.
      • Steroids play a role in hormone production and cell signaling.
      • Glycolipids are involved in cell recognition and communication.

    Proteins: Chemical Blocks of Life

    • Proteins are the most abundant and functionally diverse molecules in living systems.
    • They serve numerous functions in the body.
      • They regulate metabolism as enzymes and polypeptide hormones.
      • Contractile proteins in muscle facilitate movement.
      • Structural proteins (e.g. collagen, elastin, keratin) provide framework and support for tissues like skin, hair, and nails.
      • Transport proteins (e.g. hemoglobin, albumin) carry essential molecules in the bloodstream.
      • Immunoglobulins defend the body against pathogens.
      • They form coagulation factors to control bleeding.
      • They are essential for growth and development.
      • They act as secondary messengers in cell signaling.
    • Amino Acids: building blocks of proteins, characterized by having both an amino group (NH2) and a carboxylic acid group (COOH).
      • Twenty naturally occurring amino acids are used by cells to synthesize proteins.
      • They are connected by peptide bonds to form proteins.

    Enzyme Activity Regulation

    • Enzyme activity can be regulated in various ways to control metabolic pathways.
    • Zymogen Activation:
      • Certain enzymes are secreted in an inactive form (proenzymes or zymogens).
      • They are activated by specific peptide bond hydrolysis at the site of action.
      • Examples include pepsinogen to pepsin, trypsinogen to trypsin, and plasminogen to plasmin.
    • Covalent Modification:
      • Enzymes can be regulated by adding or removing phosphate groups to specific amino acids (e.g. serine, tyrosine).
      • Phosphorylation can activate or deactivate enzymes, depending on the enzyme.
      • This results in two interconvertible forms of the enzyme (phosphorylated and dephosphorylated).
    • Allosteric Modulation:
      • Allosteric enzymes bind to effectors, which are small regulatory molecules, at allosteric sites distinct from the active site.
      • Positive effectors increase enzymatic activity.
      • Negative effectors decrease enzymatic activity.
    • Feedback Inhibition:
      • A type of allosteric regulation where the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.
      • This occurs at the committed-step enzyme, the first irreversible enzyme unique to the pathway.
    • Enzyme Synthesis Regulation:
      • Cells can adjust the amount of an enzyme by altering the rate of enzyme synthesis.
      • Induction increases enzyme synthesis.
      • Repression decreases enzyme synthesis.
      • This type of regulation is slow and long-term, occurring over hours to days.

    Carbohydrates

    • Fructose is a component of sucrose and gives a sweet taste
    • Sucrose derivatives are sometimes used by diabetics and obese patients as an alternative to glucose.
    • High levels of fructose increase hunger and sugar cravings.

    Polysaccharides

    • Polysaccharides consist of high molecular polymers
    • Glycogen is a branched form of polysaccharides found in animals and humans
    • Starch is a plant storage form of carbohydrates and the most abundant carbohydrate in diets.
    • Starch consists of two main molecules Amylose and Amylopectin.
    • Dextrins are highly branched and are intravenously infused as plasma volume expanders.
    • Cellulose is a structural form of carbohydrates in plants and humans cannot digest it.
    • Fiber helps with digestion and constipation.

    Carbohydrate Derivatives

    • Deoxy-monosaccharides have -OH replaced by –H, like Deoxyribose sugar
    • Amino Sugar has an -OH replaced by –NH2
    • Sugar Acids have –CH2OH oxidized to –COOH, like Glucuronic acid

    Fatty Acids

    • Long chain fatty acids contain more than 12 carbon atoms
    • Palmitic acid is a long-chain fatty acid with 16 carbons
    • In the human body, fatty acids with an even number of carbon atoms predominate

    Rancidity

    • Lipids are exposed to light, heat, moisture, and bacteria
    • The process of oxidation of lipids leads to rancidity
    • Rancidity can be inhibited by adding antioxidants like vitamins A and E.

    Essential Fatty Acids (EFA)

    • EFA must be obtained from the diet
    • Linoleic acid is the precursor of ω-6 fatty acids.
    • α-linolenic acid is the precursor of ω-3 fatty acids.
    • Both ω-6 and ω-3 fatty acids are important for growth and development.

    Lipids in Health and Disease

    • Lipids act as structural components of biological membranes.
    • Lipids store and supply energy.

    High Energy Bonds

    • High energy bonds are represented by the symbol “~ “
    • ATP (Adenosine Triphosphate) contains high energy bonds between each phosphate group.
    • ATP is the main energy currency in the body.
    • Sulfer compounds such as Acetyl CoA contain high energy bonds.

    Non-covalent Bonds

    • Non-covalent bonds are reversible and vital molecular interactions.
    • Ionic bonds involve a transfer of an electron.
    • Electrostatic interactions and hydrogen bonding are also types of non-covalent bonds.

    Ionic Bonds

    • Ionic bonds are usually found in dry forms such as salts
    • They are present in compounds throughout the human body.
    • Ionic compounds are generally water soluble.

    Biomedical Importance of Ionic Bonds

    • Ionic bonds play an important role in shaping the tertiary and quaternary structures of proteins.
    • Ionic bonds are involved in catalytic reactions of enzymes.

    Hydrogen Bonds

    • Hydrogen bonds involve the electrostatic attraction between a hydrogen atom and an atom containing a lone pair of electrons.
    • Hydrogen bonds are considerably weaker than covalent bonds.

    Enzymes

    • Enzymes speed up biochemical reactions.
    • Non-protein components of enzymes are called cofactors or prosthetic groups.
    • If the non-protein component of the holo enzyme is an inorganic group it is called cofactor.
    • If the non-protein part is bound so tightly to the apoenzyme and is difficult to remove without damaging the enzyme it is called a prosthetic group.

    Isoenzymes (Isozymes)

    • Isoenzymes have similar catalytic activity, act on the same substrate, and produce the same product.
    • LDH (Lactate dehydrogenase) exists in five different forms.

    Rate Limiting Steps

    • The rate limiting step in any reaction is its slowest step.
    • It sets the pace for the entire reaction.

    Properties of Enzymes

    • Enzyme molecules contain a special pocket or cleft called the active site.
    • The substrate (The molecule or reactant that the enzyme acts upon to form products) binds the enzyme non-covalently.
    • The substrate binds to the enzyme by reversible interactions formed by Hydrogen bonds and Hydrophobic interactions.

    Enzyme Inhibition

    • Lead may non-competitively inhibit important enzymes in the heme synthesis pathway.
    • Cyanide leads to irreversible inhibition of enzymes responsible for ATP synthesis.

    Enzymes Clinical Use: Diagnosis of Diseases

    • Plasma enzymes can be classified into two major groups: functional plasma enzymes and non-functional plasma enzymes.
    • Many diseases that cause tissue damage result in an increased release of intracellular enzymes into the plasma.

    Carbohydrates

    • Carbohydrates are hydrates of carbon containing hydrogen and oxygen in a ratio of 2:1
    • The general molecular formula is (CH2O)n, where n > 3
    • There are three major classes of carbohydrates:
      • Monosaccharides
      • Oligosaccharides
      • Polysaccharides
    • Monosaccharides are simple sugars
    • The most abundant monosaccharides in nature are the 6-carbon sugars like glucose and fructose
    • Monosaccharides contain an aldehyde group (aldoses) or a keto group (ketoses)
    • The carbon atom that is double bonded to an oxygen atom forms a carbonyl group
    • Asymmetric carbon atom is a carbon atom attached to 4 different groups or atoms
    • Isomers have the same chemical formula, but different structures
    • Examples of isomers include glucose, fructose, and galactose
    • The most abundant oligosaccharides are disaccharides
    • Maltose is the malt sugar and is the major degradative product of starch
    • Maltose is hydrolyzed to two molecules of glucose
    • Lactose is composed of glucose and galactose subunits and is found exclusively in the milk of mammals
    • Lactose is the least sweet sugar
    • Lactose is the only source of galactose which plays an integral role in neural and immunological processes
    • Lactose also plays a role in the absorption of Calcium, Copper, and Zinc
    • Lactose intolerance is the inability to fully digest lactose, leading to diarrhea, gas, and bloating
    • Sucrose is composed of glucose and fructose subunits
    • Sucrose is also known as table sugar
    • Glucuronic Acid serves as a detoxification product for the body especially for bilirubin formed during heme breakdown
    • Immature babies have low levels of glucuronic acid which makes them more prone to jaundice
    • Patients with liver failure are more prone to drug toxicity due to decrease in glucuronic acid synthesis
    • Sugar alcohols have COOH reduced to CH2OH
    • Mannitol is used as a diuretic to help the body produce more urine
    • Sorbitol is used to relieve constipation and as an artificial sweetener
    • Sorbitol is normally present in some fruits
    • Excess use of sorbitol leads to bloating and digestion problems

    Importance of Carbohydrates

    • Carbohydrates provide a significant fraction of dietary calories
    • Carbohydrates are a storage form of energy
    • Carbohydrates are a component of cell membranes
    • Although a common source of energy, carbohydrates are not essential nutrients
    • Carbohydrates are more readily converted than proteins or fats into glucose
    • Carbohydrates induce early but short-term satiety when compared to proteins and fat

    Carbohydrates and disease

    • Abnormal metabolism of glucose is related to many serious diseases, especially diabetes mellitus
    • Inborn errors in carbohydrate metabolism can cause wide range of abnormalities including mental retardation

    Fatty Acids

    • Fatty acids are long-chain carboxylic acids that are commonly found in animal fats and vegetable oils
    • Some fatty acids are saturated, containing no double bonds
    • Some fatty acids are unsaturated, containing one or more double bonds
    • The introduction of a cis double bond causes the fatty acid to bend or kink at that position
    • Cis double bonds are present in natural foods
    • Trans double bonds predominate in artificially produced foods
    • In humans, the majority of fatty acids are saturated or monounsaturated
    • The presence of double bonds in some fatty acids helps maintain fluidity of membrane lipids
    • Fatty acids can be categorized based on chain length
    • Short-chain fatty acids contain 2 to 6 carbon atoms.
    • Medium-chain fatty acids contain 7-12 carbon atoms
    • Long-chain fatty acids contain 14-22 carbon atoms
    • High-fiber foods encourage the production of short-chain fatty acids by the human body
    • Medium chain fatty acids are mainly present in coconut oil and dairy products
    • They are now gaining popularity as a healthy diet component and as a dietary supplement

    Enzyme Regulation

    • Enzymes are biological catalysts that speed up chemical reactions
    • Enzyme activity can be regulated by:
      • Zymogens (Pre-enzymes)
      • Covalent Modification
      • Allosteric Modulation
      • Feedback Inhibition
      • Enzyme Synthesis
    • Zymogens are considered a protective mechanism, preventing auto-digestion of tissues
    • Many enzymes are regulated by covalent modification, most often by the addition or removal of phosphate groups
    • Enzymes may be activated by phosphorylation and inactivated by dephosphorylation, or vice versa
    • Some enzymes bind to effectors, known as allosteric enzymes
    • Effectors are small, regulatory molecules that bind to allosteric sites on the enzyme
    • Allosteric effectors that increase the catalytic activity of the enzyme are known as positive effectors
    • Allosteric effectors that reduce catalytic activity are negative effectors
    • Feedback inhibition is a type of allosteric regulation in which the end product inhibits the activity of the enzyme
    • Cells can also regulate the amount of enzyme present by altering the rate of enzyme synthesis
    • The induction or repression of enzyme synthesis leads to an alteration in the total number of active sites
    • Clinical Implications: Lead may non-competitively inhibit important enzymes in the heme synthesis pathway leading to anemia
    • Reducing agents like vitamin C and vitamin E can regain the activity of the enzyme
    • Routine supplementation of these vitamins is therefore advised for people living or working in areas of high pollution.

    Enzyme Poison

    • Irreversible inhibition, also known as enzyme poisoning, is when an inhibitor combines covalently and irreversibly to the functional group of the enzyme, destroying it.
    • This type of inhibition decreases the Vmax while the Km stays the same.
    • No competition between substrate and inhibitor because the inhibitor has no structural resemblance to the substrate.
    • Clinical implications: Organophosphates found in most pesticides, when accidently ingested or inhaled, lead to irreversible inhibition of enzymes controlling nerve signals in the body.
    • Cyanide leads to irreversible inhibition of enzymes responsible for ATP synthesis.

    Enzymes in Clinical Use:

    • Plasma enzymes can be classified into two major groups:
    • Functional Plasma Enzymes: enzymes secreted into the plasma by certain organs and performing a specific function in the plasma
    • Non-functional plasma enzymes: these enzymes are normally intracellular
    • In healthy individuals, the levels of these enzymes are fairly constant
    • Many diseases that cause tissue damage result in an increased release of intracellular enzymes into the plasma.
    • The degree of elevation of a particular enzyme in plasma is often useful in evaluating the diagnosis and prognosis for the patient.

    Carbohydrates

    • Fructose is a very sweet monosaccharide
    • Sucrose derivatives are sometimes used by diabetics and obese patients as an alternative to glucose
    • High levels of fructose increase hunger and sugar cravings
    • Polysaccharides are the most abundant form of carbohydrates in nature
    • Glycogen is the branched form of polysaccharides from animal sources and the main storage form in humans
    • Starch is the plant storage form of carbohydrates and the most abundant carbohydrate in the diet
    • Dextrins are highly branched and used for intravenous infusion as plasma volume expanders in the treatment of hypovolumic shock
    • Cellulose, an unbranched polysaccharide, is the structural form of carbohydrates in plants
    • Humans cannot digest cellulose, but it is consumed in the diet as fiber
    • Fiber helps keep food moving through the gut and prevent constipation

    Carbohydrate Derivatives

    • Deoxy-monosaccharides replace –OH with –H, like deoxyribose sugar in DNA
    • Amino sugars replace –OH with –NH2, becoming –osamaine such as glucosamine in proteoglycans
    • Sugar acids oxidize –CH2OH to –COOH, like glucuronic acid, which plays a role in detoxification in the liver

    Amino Acids

    • Most amino acids have a central carbon atom (α-carbon) with a hydrogen atom, an α-amino group (NH3+), an α-carboxyl group (COO–), and an R group (side chain)
    • The side chain or R group distinguishes each amino acid chemically
    • Some amino acids have unique groups in their side chains:
      • Sulfur group (methionine and cysteine)
      • Hydroxyl group (serine, threonine and tyrosine)
      • Imino group (NH instead of NH2) (proline)

    Classification of Amino Acids

    • Structure: Aliphatic (open chain of carbon and hydrogen) or aromatic (contain benzene ring)
    • Charge: Neutral (no charges), acidic (can donate a proton and carry a negative charge), or basic (can accept protons and carry a positive charge)
    • Biological Importance: Essential (must be taken in diet), non-essential (can be synthesized), semi-essential (histidine and arginine, can be synthesized but may need supplementation in certain conditions)
    • Polarity: Polar (hydrophilic, can be neutral, acidic, or basic) or non-polar (hydrophobic, always neutral)

    Significance of Nonpolar Amino Acids

    • In aqueous solutions, nonpolar amino acids tend to cluster together in the interior of proteins, away from water
    • This "hydrophobic effect" helps give proteins their three-dimensional shape

    Why form chemical bonds?

    • Atoms strive to reach the most stable (lowest-energy) state
    • Many atoms become stable when their valence shell is filled with electrons or they satisfy the octet rule

    Classification of Bonds

    • Covalent Bonds:
      • Strongest type of bonds
      • Formed by sharing electrons between adjacent atoms
      • Can be polar or nonpolar
    • Non-covalent Bonds:
      • Weaker than covalent bonds
      • Important for temporary interactions
      • Examples: hydrogen bonds, electrostatic interactions

    Covalent Bonds of Biomedical Importance

    • Glycosidic bonds: Join a carbohydrate molecule to another molecule
    • Peptide bonds: Join amino acids together to form proteins

    Non-covalent Bonds of Biomedical Importance

    • Hydrogen bonds: Important for DNA structure, protein folding, and other biological interactions
    • Electrostatic interactions: Occur between positively and negatively charged atoms, play a role in protein structure

    Enzymes

    • Biological catalysts that speed up chemical reactions in living organisms
    • Are proteins
    • Not consumed or changed in the reactions they catalyze

    Importance of Enzymes

    • Many reactions required for life would proceed too slowly without enzymes
    • Enzymes lower the energy barrier of reactions, making them occur at a faster rate

    Types of Enzymes

    • Simple Enzyme: Made only of protein molecules
    • Holoenzyme: Made of protein (apoenzyme) and a non-protein component (coenzyme)

    Enzyme Inhibition

    • Competitive Inhibition: Inhibitor competes with the substrate for the active site of the enzyme
    • Non-Competitive Inhibition: Inhibitor binds to the enzyme at a site other than the active site, changing the enzyme's shape and reducing its activity
    • Irreversible Inhibition (Enzyme Poison): Inhibitor binds covalently and irreversibly to the enzyme, destroying its function.

    Clinical Applications of Enzymes

    • Diagnosis of Disease: Measuring levels of certain enzymes in the blood can indicate tissue damage or disease
    • Therapeutic Use: Enzymes can be used as medications to treat certain conditions, such as digestive disorders or genetic diseases

    Plasma Enzymes

    • Functional Plasma Enzymes: Secreted into the plasma by specific organs and perform a function in the blood
    • Non-functional Plasma Enzymes: Released from cells during normal cell turnover, they have no physiologic function in the plasma. Elevated levels can indicate tissue damage.

    Glucuronic Acid

    • Immature babies have low levels of glucuronic acid which makes them more prone to jaundice due to the accumulation of bilirubin.
    • Bilirubin is not detoxified by glucuronic acid in severe cases, which can lead to "kernicterus."
    • Kernicterus can affect the brain, leading to mental retardation and vision problems.
    • Patients with liver failure are prone to drug toxicity due to a decrease in glucuronic acid synthesis and the inability to detoxify drugs.

    Sugar Alcohols

    • Sugar alcohols have COOH reduced to CH2OH.
    • Mannitol is used as a diuretic to help the body produce more urine in case of edema.
    • Sorbitol is used to relieve constipation and as an artificial sweetener for low-calorie diets.
    • Sorbitol has nearly 50% less calories than normal sugars and stimulates taste buds.
    • Sorbitol is present in fruits like cherries.
    • Excess sorbitol use can lead to bloating and digestion problems.

    Carbohydrates

    • Carbohydrates provide dietary calories for most organisms.
    • Carbohydrates supply and act as a storage form of energy in the body.
    • Carbohydrates serve as cell membrane components that mediate intercellular communication.
    • 1 gram of carbohydrates provides 4 calories.
    • Carbohydrates are not essential nutrients because humans can obtain their daily energy requirement from proteins and fats.
    • Carbohydrates are more readily converted than proteins or fats into glucose.
    • All carbohydrates are broken down to glucose upon digestion.
    • Glucose is transported to cells for energy production.
    • Carbohydrates induce early but short-term satiety compared to proteins and fats.

    Carbohydrates and Disease

    • Abnormal glucose metabolism is related to many serious diseases, including diabetes mellitus and some cancers.
    • Inborn errors in carbohydrate metabolism can cause abnormalities such as mental retardation and hepatomegaly.

    High Energy Bonds

    • High energy bonds are represented by the symbol "~".
    • High energy bonds are broken to yield energy, driving metabolic processes.

    High Energy Compounds

    • Phosphate compounds: ATP, ADP, GTP, GDP, UTP, UDP, UDP-glucose, creatine phosphate, arginine phosphate, 1,3-bisphosphoglycerate, phosphoenol pyruvate, carbamoyl phosphate.
    • ATP (adenosine triphosphate) contains high energy bonds between each phosphate group, known as phosphoric anhydride bonds.
    • ATP is the main energy currency in the body.
    • Sulfur compounds: Acetyl CoA, Succinyl CoA, acyl CoA, HMG CoA.

    Non-Covalent Bonds

    • Non-covalent bonds are reversible and vital molecular interactions.
    • Non-covalent bonds include ionic bonds, electrostatic interactions, and hydrogen bonding.

    Ionic Bonds

    • Ionic bonds involve the transfer of an electron, resulting in an anion (negative charge) and a cation (positive charge).
    • Opposite charges attract, forming a molecule.
    • Ionic bonds are found in dry forms, like salts, and in compounds throughout the human body.
    • Ionic compounds are generally water-soluble.
    • Ionic bonds play a role in protein folding, shaping tertiary and quaternary structures.
    • Ionic bonds are involved in enzyme catalytic reactions.

    Hydrogen Bonds

    • Hydrogen bonds involve electrostatic attraction between a hydrogen atom and an atom with a lone pair of electrons.
    • Hydrogen bonds are found in DNA between adenine-thymine and guanine-cytosine base pairs.
    • Breaking of hydrogen bonds is required for DNA replication.
    • Hydrogen bonding plays a role in protein folding.

    Electrostatic Interactions

    • Electrostatic interactions occur between positively and negatively charged atoms.
    • They can be repulsive or attractive.
    • Electrostatic interactions play a role in protein 3D structure formation.

    Enzymes

    • Enzymes are protein catalysts for chemical reactions in biological systems.
    • Enzymes increase the rate of chemical reactions within living cells without being changed or consumed.

    Enzyme Importance

    • Many reactions required for living cells would not proceed fast enough at the pH and temperature of the body without enzymes.
    • Cellular reactions have high energy barriers, requiring high energy for the reaction to take place.
    • Enzymes lower the energy barrier, increasing the rate of reaction without changing the reaction itself.

    Enzyme Nature

    • Simple enzyme: made of only protein molecules.
    • Holo enzyme: made of proteins and non-protein components.
    • Apoenzyme: the protein component of the holo enzyme.
    • Coenzyme: an organic non-protein component of the holo enzyme.

    Enzyme Inhibition

    • Non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen, inhibit cyclooxygenase (COX); this enzyme is responsible for the formation of pain, fever, and inflammation mediators.
    • NSAIDs can be used as analgesics, antipyretics, and anti-inflammatories.

    Factors Affecting Enzyme Activity

    • Temperature:
      • Reaction velocity increases with temperature until a peak velocity is reached.
      • Optimum temperature for most human enzymes is 37°C.
      • At 0°C, enzymes are inactive.
      • Above 40°C, enzyme activity decreases due to denaturation.
    • pH:
      • Concentration of protons (H+) affects reaction velocity.
      • Catalytic processes require specific chemical groups to be ionized or unionized for interaction.
      • Optimum pH varies from enzyme to enzyme and reflects the pH at which the enzyme functions in the body.
    • Substrate Concentration:
      • Rate of reaction is directly proportional to substrate concentration until all enzymes are saturated.
      • At high substrate concentrations, the rate becomes constant (Vmax).
      • Different organs may have different Km values for the same enzyme, reflecting different affinities for the substrate.
    • Enzyme Concentration:
      • Rate of reaction is directly proportional to enzyme concentration until a maximum rate is reached.
      • Additional enzyme does not affect further rate increase after the maximum rate is reached.
    • Product Concentration:
      • As products acculumate, enzyme activity decreases due to:
        • pH changes
        • Product competing with substrate for the active site
        • Product binding to the allosteric site (in case of allosteric enzymes)

    Regulation of Enzyme Activity

    • Enzyme activity is regulated by:
      • Zymogen activation:
        • Some enzymes are secreted in an inactive form called "proenzymes" or "zymogens".
        • These enzymes are activated at the site of action through specific peptide bond hydrolysis.
        • Examples: pepsinogen to pepsin, trypsinogen to trypsin, plasminogen to plasmin.
        • Activated enzymes cannot be reconverted to proenzymes.

    Long Chain Fatty Acids

    • Contain more than 12 carbon atoms, with Palmitic acid (16 carbons) being an example.
    • Predominantly found in animal tissues and diets.
    • In humans, even-numbered carbon chains (16, 18, or 20) are most common.
    • Longer-chain fatty acids (>22 carbons) are present in the brain.

    Rancidity

    • Occurs when lipids are exposed to light, heat, moisture, and bacterial action.
    • Results in changes to the odor, taste, and acidity of the fat.
    • Hydrolytic rancidity: Short-chain fatty acids are liberated due to slight hydrolysis, producing a bad odor.
    • Oxidative rancidity: Oxidation of unsaturated fatty acids forms peroxides, aldehydes, and ketones.
    • Can be inhibited by adding antioxidants (e.g., vitamins A, E), and storing fat in a cold, clean, dark, and dry place.

    Fatty Acid Numbering

    • Two systems are used to number carbon atoms in a fatty acid.

    Essential Fatty Acids (EFA)

    • Lipids can be obtained from the diet or synthesized by the body.
    • EFAs are required in the diet and include:
      • Linoleic acid (precursor of ω-6 fatty acids)
      • α-linolenic acid (precursor of ω-3 fatty acids)
    • Both ω-6 and ω-3 fatty acids are critical for growth and development.
    • ω-3 fatty acids are found in salmon, sardines, and flaxseeds.
    • ω-6 fatty acids are present in walnuts, peanuts, corn, and sunflower oils.
    • Deficiency in EFAs can lead to hair loss, low platelets, and intellectual disability.

    Lipids in Health and Disease

    • Lipids play essential roles in the body, acting as:
      • Structural components of biological membranes
      • Energy storage and supply (1 g of dietary lipids provides 9 calories).
    • Nonpolar amino acid side chains interact with the lipid environment in proteins located in hydrophobic environments, such as membranes.
    • Polar amino acid side chains participate in hydrogen bond formation, which helps stabilize protein structure.
    • The side chain of cysteine contains (-SH), a component of active sites in many enzymes.
    • It also forms disulfide bonds that stabilize protein structure.

    Sickle Cell Anemia

    • Results from the replacement of polar glutamate with nonpolar valine at the sixth position in the β subunit of hemoglobin A.
    • This change causes red blood cells to become sticky when oxygen levels are low, leading to blockages in blood vessels and severe pain.

    Amphoteric Property of Amino Acids

    • Amino acids possess both acidic (-COOH) and basic (-NH2) groups, allowing them to act as acids and alkalis in solution.
    • Neutral amino acids fully ionize to form dipolar ions (zwitterions) with equal positive and negative charges.
    • Isoelectric point (IEP) or pI is the pH where an amino acid has equal positive and negative charges and is electrically neutral.
    • At their IEP, amino acids do not migrate towards an electrode and precipitate.
    • Plasma proteins can form an efficient buffer system due to their amphoteric nature, which is important for maintaining blood pH.

    Biomedical Importance of Hydrogen Bonds

    • They play a crucial role in the structure and properties of many molecules, including:
      • DNA: Two hydrogen bonds between adenine and thymine, three between guanine and cytosine.
      • Protein folding.

    Electrostatic Interactions

    • Occur between positively and negatively charged atoms, resulting in attraction or repulsion.
    • Play a role in determining the three-dimensional structure of proteins.

    Enzyme Properties and Importance

    • Enzymes are protein catalysts that accelerate chemical reactions in biological systems.
    • They do not undergo changes or get consumed during the reaction.
    • Importance: Many reactions required for cell survival would not proceed fast enough at body temperature and pH without enzymes.
    • Enzymes lower the energy barrier of reactions, increasing their rate without altering the reaction itself.

    Enzyme Characteristics

    • Simple enzymes: Composed only of protein molecules.
    • Holoenzymes: Made up of protein and non-protein components.
      • Apoenzyme: The protein component.
      • Coenzyme: The non-protein component (organic).
    • Induced Fit Model: Interaction of the substrate with the enzyme induces a conformational change in the enzyme, resulting in the formation of a stronger binding site and repositioning of amino acids to form the active site.
    • Efficiency: Most enzyme-catalyzed reactions are highly efficient (10^3 to 10^8 times faster than uncatalyzed reactions).
    • Specificity: Enzymes are highly specific, acting on one or a few substrates and catalyzing only one type of reaction.
      • Absolute specificity: An enzyme acts on only one substrate.
      • Bond specificity: Enzymes are specific for a particular bond (e.g., esterases, peptidases, glycosidases).
    • Regulation: Enzyme activity can be regulated (increased or decreased) to meet cellular needs.
    • Location within the cell: Many enzymes are localized in specific organelles, compartmentalizing reactions and preventing interference with other reactions.
      • This provides a favorable environment for the reaction and helps organize cellular enzymes into pathways.

    Mechanism of Enzyme Action

    • Substrate concentration: If the substrate concentration is much lower than the Michaelis-Menten constant (Km), the reaction velocity is directly proportional to substrate concentration (first-order).
      • If substrate concentration is much higher than Km, the velocity plateaus at Vmax (zero-order).
    • Enzyme concentration: The rate of the reaction is directly proportional to enzyme concentration until a maximum rate is reached.
    • Product concentration: As product accumulates, enzyme activity decreases due to factors such as:
      • pH changes.
      • Product competing with the substrate for the active site.
      • Product binding to an allosteric site (for allosteric enzymes).

    Regulation of Enzyme Activity

    • Zymogen activation: Some enzymes are secreted in inactive forms (proenzymes or zymogens) that are activated when needed.
      • Specific peptide bonds are hydrolyzed at the site of action.
      • Examples: Pepsinogen to pepsin, Trypsinogen to trypsin, plasminogen to plasmin.
      • Once activated, the enzyme cannot be returned to its inactive proenzyme form.

    Carbohydrates

    • Carbohydrates are hydrates of carbon containing hydrogen and oxygen in a ratio of 2:1.
    • The general molecular formula for carbohydrates is (CH2O)n, where n > 3.
    • There are three major classes of carbohydrates:
      • Monosaccharides (mono = one)
      • Oligosaccharides (oligo= few) 2-10 monosaccharide units.
      • Polysaccharides (Poly = many) >10 monosaccharide units.

    Monosaccharides

    • Monosaccharides are simple sugars.
    • Monosaccharides are named based on the number of carbon atoms: trioses (C3), tetroses (C4), pentoses (C5), hexoses (C6), heptoses (C7).
    • Glucose and fructose are the most abundant monosaccharides in nature.
    • Monosaccharides can contain either an aldehyde group (aldoses) or a keto group (ketoses).
    • An asymmetric carbon atom is a carbon atom attached to 4 different groups or atoms.
    • Isomers are compounds with the same chemical formula but different structures.

    Oligosaccharides

    • Disaccharides are the most abundant oligosaccharides.
    • Maltose: Maltose is the degradative product of starch. It is hydrolyzed to two molecules of glucose and is also known as malt sugar.
    • Lactose: Lactose is composed of glucose and galactose subunits and is found exclusively in mammal milk (milk sugar). Lactose is the only source of galactose, which is essential for neural and immunological processes.
    • Sucrose: Sucrose is composed of glucose and fructose subunits and is also known as cane sugar.

    Fatty acids

    • Fatty acids are long-chain carboxylic acids.
    • The hydrophobic portion of the fatty acid is predominant, making it water-insoluble.
    • Fatty acid chains can be saturated (no double bonds) or unsaturated (one or more double bonds).
    • Cis double bends are present in natural foods like salmon, nuts, and olive oil.
    • Trans double bonds predominate in artificially produced foods and are linked to an increased risk of atherosclerosis.
    • Addition of double bonds decreases the melting temperature (Tm) of a fatty acid, while increasing chain length increases the Tm.
    • Fatty acids are classified according to chain length:
      • Short chain fatty acids (2 to 6 carbon atoms) are found in high-fiber foods.
      • Medium chain fatty acids (7-12 carbon atoms) are present in coconut oil and dairy products and may improve gut health.
      • Long-chain fatty acids contain more than 12 carbon atoms.

    Chemical Bonds

    • Atoms form chemical bonds to reach a stable, low-energy state.
    • Bonds can be classified as covalent (strong) or non-covalent (weak).
    • Covalent bonds form by sharing electrons between adjacent atoms.
      • Polar covalent bonds occur between atoms with different electronegativities.
      • Nonpolar covalent bonds form between atoms of the same element or atoms that share electrons equally.

    Bond of Biomedical Importance

    • Glycosidic bonds: These bonds join a carbohydrate molecule to another molecule.

    Enzymes

    • Enzymes are biological catalysts that speed up reactions.
    • Active site: Enzymes contain a special pocket or cleft called the active site which binds substrate.
      • The active site is formed by the folding of the protein.
      • The active site contains amino acid side chains that participate in substrate binding and catalysis.
    • Substrate: the molecule or reactant that the enzyme acts upon to form products.
    • Enzyme-substrate (ES) complex: formed when the substrate binds non-covalently to the active site of the enzyme.
    • Enzyme-product (EP) complex: formed when the ES complex undergoes a chemical reaction at the active site.
      • The EP complex dissociates into enzyme and product.

    Enzyme Regulation

    • Zymogens: inactive precursor forms of enzymes that are activated by proteolytic cleavage.
    • Covalent Modification: Many enzymes are regulated by the addition or removal of phosphate groups, often to serine or tyrosine residues on the enzyme.
    • Allosteric Modulation: Allosteric enzymes bind to effectors, which are small, regulatory molecules that bind to allosteric sites on the enzyme. These sites are different from the active site.
      • Positive effectors increase the catalytic activity of the enzyme.
      • Negative effectors reduce the catalytic activity of the enzyme.
    • Feedback inhibition: A type of allosteric regulation where the end product of a metabolic pathway inhibits the activity of an enzyme early in the pathway.
    • Committed-Step enzyme: The first irreversible enzyme specific to a metabolic pathway (not necessarily the rate-limiting step).
      • It commits the substrate to the pathway.
    • Enzyme synthesis: Cells can regulate the amount of enzyme present by altering the rate of enzyme synthesis.
      • Induction (increase) or repression (decrease) of enzyme synthesis changes the total number of active sites.

    Carbohydrates

    • Sucrose is obtained from cane sugar and is also present in fruits.
    • Fructose in sucrose makes it very sweet.
    • Sucrose derivatives are sometimes used by diabetics and obese patients to provide sweet taste with less concentration.
    • High levels of fructose may increase hunger and sugar cravings.
    • Polysaccharides are complex carbohydrates.
    • Glycogen is the branched form of polysaccharide from animal sources and is the main storage form in humans.
    • Starch is the plant storage form of carbohydrates and is the most abundant carbohydrate in the diet.
    • Starch is found in potatoes, rice, and pasta and consists of amylose and amylopectin.
    • Dextrins are highly branched and are used for intravenous infusion as a plasma volume expander.
    • Cellulose is a structural carbohydrate in plants that humans cannot digest.
    • Cellulose is consumed as dietary fiber.
    • Dietary fiber helps the digestive system by keeping food moving through the gut and preventing constipation.
    • Carbohydrate derivatives are sugar molecules that have been modified.
    • Deoxy-monosaccharides are modified sugars where an -OH group is replaced by an -H group.
    • Deoxyribose is an example of a deoxy-monosaccharide and it forms DNA.
    • Amino sugars are modified sugars where an -OH group is replaced by an -NH2 group. Glucosamine is an example of an amino sugar.
    • Sugar acids are modified sugars where the -CH2OH group is oxidized to a -COOH group. Glucuronic acid is an example of a sugar acid and it's synthesized in the liver.

    Lipids

    • Lipids are fats and oils.
    • Some fatty acids are saturated, containing no double bonds.
    • Some fatty acids are unsaturated, containing one or more double bonds.
    • Double bonds in natural fatty acids are in the cis (functional group on the same side) configuration.
    • The introduction of a cis double bond causes the fatty acid to bend or kink at that position.
    • Trans (functional group on opposite sides) double bonds predominate in artificially produced foods, and are associated with an increased risk of atherosclerosis.
    • The majority of fatty acids in humans are saturated or monounsaturated.
    • The addition of double bonds decreases the melting temperature of a fatty acid.
    • Increasing the chain length increases the melting temperature of a fatty acid.
    • Fatty acids can be classified by chain length:
      • Short chain fatty acids (SCFA) contain 2 to 6 carbon atoms.
      • Medium chain fatty acids (MCFA) contain 7 to 12 carbon atoms.
      • Long chain fatty acids (LCFA) contain more than 12 carbon atoms.
    • In the human body, fatty acids with an even number of carbon atoms (16, 18, or 20) predominate.
    • Lipids exposed to light, heat, moisture, and bacterial action can change into rancid fat.
    • Rancid fat has a bad odor, taste, and is acidic in reaction.
    • Rancidity is caused by hydrolysis of fat leading to liberation of short chain fatty acids.
    • Rancidity is also caused by oxidation of unsaturated fatty acids.
    • Rancidity can be inhibited by the addition of antioxidants, such as vitamins A and E.
    • Essential fatty acids (EFAs) are lipids that are necessary for growth and development.
    • The two essential fatty acids include:
      • Linoleic acid, the precursor of ω-6 fatty acids.
      • α-linolenic acid, the precursor of ω-3 fatty acids.
    • Essential fatty acid deficiency can occur in infants fed diets deficient in EFAs.
    • Symptoms of essential fatty acid deficiency include hair loss, low platelets, and intellectual disability.
    • Lipids play many important roles in health, including:
      • Structural elements in biological membranes
    • Store and supply energy
    • The energy content of 1 gram of dietary lipids is about 9 Cal.

    Enzymes

    • Enzymes are biological catalysts that speed up the rate of chemical reactions without being consumed in the process.
    • Each enzyme has a unique active site that fits with its specific substrate.
    • The pH of a solution can affect the activity of an enzyme.
    • Extremes of pH can lead to denaturation of the enzyme and loss of its function.
    • The activity of an enzyme is influenced by the concentration of its substrate.
    • At fixed enzyme concentration, pH, and temperature, the activity of enzymes is increased by increasing substrate concentration.
    • Increasing the substrate concentration increases the enzyme activity and the rate of the enzyme-catalyzed reaction until a maximum (maximal velocity) is reached.
    • The maximal velocity (Vmax) is the maximum rate of reaction when all enzyme active sites are saturated with substrate.
    • Km is the affinity of the enzyme for its substrate.
    • Km is the concentration of the substrate at which a given enzyme yields one-half its maximal velocity (½ Vmax).
    • Km is constant and characteristic for a particular enzyme and its substrate under standard conditions.
    • A low Km reflects a high affinity of the enzyme for its substrate.
    • A high Km reflects a low affinity of the enzyme for its substrate.
    • Inducers are substances that increase the expression of the gene coding for the enzyme.
    • Repressors are substances that decrease the gene expression of the enzyme.
    • Inhibitors are substances that decrease the velocity of an enzyme-catalyzed reaction.
    • Inhibitors can be classified into two main types:
      • Competitive inhibitors
      • Non-competitive inhibitors.
    • Competitive inhibitors bind reversibly to the same site that the substrate would normally occupy and, therefore, compete with the substrate for that site.
    • The inhibitor is structurally similar to the substrate.
    • The inhibitor binds to the enzyme and forms an [EI] complex at the active site.
    • No product is formed in the presence of a competitive inhibitor.
    • Competitive inhibition is reversible and the inhibition is removed by increasing the substrate concentration.
    • Non-competitive inhibitors bind at a different site other than the substrate-binding site, leading to conformational changes in the enzyme and reversible inactivation of the catalytic site.
    • Non-competitive inhibitors bind reversibly either to the free-enzyme or the ES complex to form the inactive complexes EI and ESI (Enzyme substrate Inhibition).
    • Non-competitive inhibitors often have no structural similarity to the substrate and the inhibition is not reversed by increasing the amount of substrate.
    • Non-competitive inhibitors lower the Vmax of the enzyme, but do not affect the Km.

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    NMD1000 Exam 2 Lecture Notes PDF

    Description

    Test your knowledge on the role of pepsin in digestion, the impact of pH on enzyme functionality, and how substrate concentration affects enzyme activity. This quiz covers key concepts related to enzymatic reactions and digestive processes.

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