CamScanner App Quiz

Enzymes

• Enzymes are biological catalysts that speed up biochemical reactions.
• Most enzymes are 3-D globular proteins.
• Some RNA molecules also act as enzymes, called ribozymes.
• Enzymes have an active site where substrates, co-factors and prosthetic groups bind.
• Active sites have a specific shape that allows them to bind to their substrates.
• Active sites contain residues that help to hold the substrate.
• The active site is divided into a binding site and a catalytic site.
• Binding sites choose the substrate and bind it, while the catalytic site performs the catalytic action of the enzyme.
• Co-factors are non-protein molecules that carry out chemical reactions not possible with standard amino acids.
• Co-factors help activate proteins.
• Apoenzyme is an enzyme without a co-factor.
• Holoenzyme is a complete enzyme with a co-factor.
• Substrates are reactants in a biochemical reaction
• When a substrate binds to an enzyme, it forms an enzyme-substrate complex.

Cofactors

• Two types of co-factors: inorganic and organic.
• Inorganic cofactors are needed for enzyme activity, examples include Mg.
• Organic cofactors (coenzymes) are needed also for enzyme activity, including examples like pyridoxal phosphate and biotin.
• Prosthetic groups are tightly bound organic cofactors.
• Coenzymes are loosely bound organic cofactors.

Enzyme Synthesis

• Enzymes are synthesized by ribosomes attached to the rough endoplasmic reticulum.
• Information for synthesis is carried by DNA.
• Intracellular enzymes are synthesized and retained in the cell for use by the cell itself.
• Examples include oxidoreductases.
• Extracellular enzymes are synthesized in a cell but secreted for use outside the cell.
• Examples include some digestive enzymes produced in the pancreas.

Characteristics of Enzymes

• Speed up reactions.
• Don't change the nature of end products.
• Highly specific.
• Sensitive to changes.
• Have a turnover number, per minute, by one enzyme. (catalytic efficiency measured as turnover number)
• Example: catalase turnover number = G x 10⁴/min

Enzyme Nomenclature

• Enzymes are named based on the reactions they catalyze.

Mechanism of Enzyme Action

• Enzymes work by lowering activation energy, which is the difference in energy between the transition state and the substrates.
• There are different types of catalytic mechanisms, in particular: Covalent catalysis, Acid-base catalysis, Proximity catalysis, and Bond strain catalysis.

Enzyme Kinetics

• Enzyme kinetics is the study of the rate of enzyme-catalyzed reactions.
• Factors affecting enzyme-catalyzed reactions include temperature, pH, and substrate concentration.

Inhibition

• Inhibitors prevent the enzyme from functioning by interacting with the active site.
• Inhibitors may block the enzyme, and can be reversible or irreversible.
• There are subtypes of reversible inhibition - competitive and uncompetitive.
• Irreversible inhibition involves a covalent attachment of the inhibitor to the enzyme.

Activation

• Enzymes can switch between inactive and active forms, which is crucial in metabolic processes.
• Cofactors can trigger this conversion.

Enzyme Specificity

• Enzymes are specific for their substrates.
• Types of enzyme specificity include bond specificity (acting on specific bonds) and group specificity (acting on specific groups within substrates).
• Other specific types include substrate specificity, optical (stereo) specificity, and dual specificity.

Lipids

• Lipids are diverse groups that include fats, oils and fatty substances, which are hydrophobic (water-fearing).
• Some lipids are amphipathic, meaning at least part is polar and part is non-polar.
• Lipids include fats, oils, waxes, and various other lipid types.
• Lipids are classified as simple or complex or derived lipids.

Complex Lipids

• Complex lipids include phospholipids, glycolipids, and lipoproteins.
• Phospholipids are essential components of cell membranes.
• Glycolipids are found in the cell membrane
• Lipoproteins are involved in lipid transport in the body.

Derived Lipids

• Derived lipids include fatty acids, sterols, and other compounds that can be derived from simple or complex lipids.

Steroids

• Steroids are specific lipids including cholesterol, testosterone, and estrogen.
• These are involved in various metabolic functions.

Chemical reactions of lipids

• Chemical reactions for certain types of lipids include
• Hydrolysis: splitting molecules with water
• Saponification: forming soap during hydrolysis
• Hydrogenation: addition of hydrogen - Unsaturated fatty acids that are converted to more saturated fatty acids through this process.
• Oxidation: reaction with oxygen and can produce peroxides or epoxides.

Functions of Lipids

• Energy storage
• Structural components of cell membranes.
• Metabolic regulators as hormones.

Membrane Proteins

• Membrane proteins can be categorized as peripheral proteins or integral proteins.

Membrane Transport

• Passive transport includes simple diffusion (molecules move through openings) and facilitated diffusion (molecules move through channels).
• Active transport includes moving against a concentration gradient.

Vitamins

• Lipidsoluble vitamins include vitamins A, D, E, and K.
• Vitamins have essential functions in physiology and metabolism.

Carbohydrates

• Carbohydrates are polyhydroxyaldehydes or polyhydroxyketones.
• Carbohydrates include monosaccharides, disaccharides and polysaccharides.
• Monosaccharides are the simplest carbohydrates.
• Examples include glucose and fructose, which are isomers.

Stereoisomers

• Epimers have different configurations differing in only one chiral center or asymmetric carbon.
• Diastereomers have differing arrangements in a molecule but are not mirror images.
• Enantiomers are mirror images.

Reactions Between Sugars

• Monosaccharides with a functional group on carbon #2 may be transformed to cyclic hemiacetals or hemiketals.
• These molecules with carbon #5 to carbon #2 bonds can undergo cyclization to produce anomeric carbons which can be either α or β depending on the configuration of the hydroxyl group (OH).
• α and β configurations differentiate anomers

Cyclic Sugars

• Cyclic hemiacetals are formed when the carbonyl group reacts with a hydroxyl group on another carbon in the same molecule.

Disaccharides

• Maltose: Glucose-Glucose linkage is α(1→4) in maltose
• Sucrose: Glucose-Fructose linkage is α(1→2) in sucrose
• Lactose: Galactose-Glucose linkage is β(1→4) in Lactose

Polysaccharides

• Starch: composed of amylose (straight chain) and amylopectin (branched chains) of glucose units linked by α(1→4) and α(1→6) glycosidic bonds.
• Cellulose: composed of extended linear chains of glucose units linked by β(1→4) glycosidic bonds.
• Glycosaminoglycans: are linear heteropolysaccharides consisting of amino sugars, often associated with proteins to form proteoglycans.
• Glycogen: branched polymer of glucose largely stored in the liver and muscles.
• Chitin: linear polymer of N-acetylglucosamine, structural component in fungal cell walls.

Nucleic Acids

• Nucleic acids are biopolymers made up of monomers called nucleotides.
• Nucleotide consists of a nitrogenous base, pentose sugar, and a phosphate group.
• There are two types of nitrogenous bases, purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil).
• A nucleoside is a sugar joined to a nitrogenous base.
• A nucleotide is a nucleoside joined to a phosphate group.

Levels of Structure

• Primary structure of nucleic acids refers to the order of nucleotides.
• Secondary structure is the 3D conformation of the polynucleotide backbone.
• Tertiary structure is supercoiling.
• Quaternary structure describes interactions between DNA and proteins.

Sugar-Phosphate Backbone

• A chain of nucleotides is connected by alternating sugar and phosphate groups forms a backbone.
• This backbone carries the genetic code in DNA or RNA.

Nucleotide-Phosphate Bonds

• Nucleotide monomers are joined together in a chain structure by bonds between the sugar and phosphate groups.

Structure of Nucleic Acids

• The components of nucleic acids include nitrogenous bases, pentose sugars, and phosphate groups.

Nucleosides

• Nucleosides are formed from a nitrogen base and a pentose sugar with a covalent link between them.

Nucleotides

• Nucleotides form by bonding a phosphate group to a nucleoside at either the 5' carbon of the sugar. Many nucleotides can assemble by bonding to each other through their phosphate group.

Other

• Denaturation describes a loss of the secondary or higher-order structures of a biological molecule..
• Glycolysis happens in the cytoplasm, and the citric acid cycle occurs in the mitochondrial matrix.

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