Enzymes and Digestion Quiz
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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 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

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

    <p>Convulsions</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 can result from defects in the globin protein of hemoglobin?

    <p>Hemolysis and oxygen delivery issues</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 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

    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.

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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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