1. pH is another critical factor influencing enzyme activity. How does pH affect enzyme function?
A. pH only affects the rate of substrate diffusion to the enzyme.
B. pH changes can alter the ionization state of amino acid residues in the active site, affecting substrate binding and catalysis.
C. Enzymes are equally active across all pH ranges.
D. pH only affects the overall concentration of the enzyme in solution.
2. Feedback inhibition is a common regulatory mechanism in metabolic pathways. In feedback inhibition, what typically acts as the inhibitor?
A. The substrate of the enzyme.
B. An intermediate product of the pathway.
C. The final product of the metabolic pathway.
D. A reactant from a completely different metabolic pathway.
3. Enzyme activity is significantly affected by temperature. What is the general effect of increasing temperature (within physiological limits) on enzyme activity?
A. Enzyme activity decreases linearly with increasing temperature.
B. Enzyme activity increases linearly with increasing temperature.
C. Enzyme activity generally increases with temperature up to an optimum, then decreases.
D. Temperature has no significant effect on enzyme activity.
4. Transferases are enzymes that catalyze the transfer of functional groups. Which of the following is a common type of reaction catalyzed by transferases?
A. Hydrolysis of peptide bonds.
B. Transfer of amino groups.
C. Oxidation of alcohols to aldehydes.
D. Racemization of chiral centers.
5. Lyases are enzymes that catalyze the breaking of bonds without hydrolysis or oxidation. What is a characteristic reaction catalyzed by lyases?
A. Formation of new bonds.
B. Isomerization reactions.
C. Removal of groups to form double bonds or rings.
D. Transfer of phosphate groups.
6. Enzymes are classified into different classes based on the type of reaction they catalyze. Which class of enzymes catalyzes oxidation-reduction reactions?
A. Hydrolases
B. Isomerases
C. Ligases
D. Oxidoreductases
7. Covalent modification is another important mechanism for enzyme regulation. Which of the following is a common type of covalent modification that regulates enzyme activity?
A. Hydrolysis
B. Oxidation
C. Phosphorylation
D. Reduction
8. Cofactors are essential for the activity of many enzymes. Which of the following BEST describes the role of a cofactor?
A. Cofactors are always proteins that bind to the enzyme to activate it.
B. Cofactors can be either inorganic ions or organic molecules that assist enzyme function.
C. Cofactors are substrates that are converted into products by the enzyme.
D. Cofactors are always consumed during the enzymatic reaction.
9. Vmax is a crucial parameter in enzyme kinetics. What does Vmax signify?
A. The substrate concentration required to reach half-maximal velocity.
B. The reaction rate at very low substrate concentrations.
C. The maximum rate of reaction when the enzyme is saturated with substrate.
D. The dissociation constant of the enzyme-substrate complex.
10. Isomerases catalyze isomerization reactions. What is the primary function of isomerases?
A. To break down large molecules into smaller ones.
B. To synthesize complex molecules from simpler ones.
C. To rearrange atoms within a molecule to form isomers.
D. To transfer electrons between molecules.
11. Enzyme assays are crucial for studying enzyme kinetics and activity. What is the PRIMARY purpose of an enzyme assay?
A. To determine the amino acid sequence of an enzyme.
B. To measure the rate of an enzyme-catalyzed reaction.
C. To purify enzymes from cell extracts.
D. To determine the three-dimensional structure of an enzyme.
12. Non-competitive inhibitors reduce enzyme activity by binding to a site other than the active site. How do non-competitive inhibitors affect enzyme kinetics?
A. They increase Km but do not change Vmax.
B. They decrease Vmax but do not change Km.
C. They increase both Km and Vmax.
D. They decrease both Km and Vmax.
13. Penicillin is a well-known antibiotic that acts as an enzyme inhibitor. Which type of enzyme does penicillin primarily inhibit in bacteria?
A. DNA polymerase
B. Ribonucleotide reductase
C. Transpeptidase
D. Reverse transcriptase
14. Enzymes are biological catalysts that accelerate chemical reactions. Which statement BEST describes how enzymes achieve this catalytic effect?
A. By increasing the activation energy of the reaction.
B. By decreasing the activation energy of the reaction.
C. By increasing the temperature of the reaction.
D. By decreasing the temperature of the reaction.
15. Uncompetitive inhibition is a type of enzyme inhibition where the inhibitor binds only to the enzyme-substrate complex. How does uncompetitive inhibition affect Km and Vmax?
A. Increases Km and Vmax.
B. Decreases Km and Vmax.
C. Increases Km and decreases Vmax.
D. Decreases Km and increases Vmax.
16. In enzyme purification, various techniques are used to isolate and purify enzymes from complex mixtures. Which technique separates proteins based primarily on their size?
A. Ion exchange chromatography
B. Affinity chromatography
C. Size exclusion chromatography
D. Isoelectric focusing
17. Lactase is an enzyme used to hydrolyze lactose, the sugar found in milk. Individuals with lactose intolerance lack sufficient lactase. What type of enzyme is lactase?
A. Oxidoreductase
B. Transferase
C. Hydrolase
D. Lyase
18. Isozymes are enzymes that catalyze the same reaction but differ in their amino acid sequence and properties. What is a significant physiological advantage of having isozymes?
A. To increase the overall rate of a single reaction in all tissues.
B. To allow for tissue-specific regulation of enzyme activity.
C. To simplify the genetic coding required for enzyme production.
D. To reduce the specificity of enzymes for their substrates.
19. Enzyme specificity refers to the ability of an enzyme to catalyze reactions with specific substrates. Which factor is MOST responsible for enzyme specificity?
A. The concentration of the enzyme in the cell.
B. The temperature at which the reaction occurs.
C. The unique three-dimensional structure of the enzyme`s active site.
D. The presence of inhibitors in the reaction mixture.
20. Irreversible enzyme inhibitors permanently inactivate enzymes. How do irreversible inhibitors typically achieve this?
A. By binding non-covalently to the active site.
B. By binding reversibly to an allosteric site.
C. By forming covalent bonds with amino acid residues in the active site.
D. By changing the pH of the enzyme`s environment.
21. Enzymes are widely used in various industrial applications. In the food industry, which enzyme is commonly used for tenderizing meat?
A. Amylase
B. Cellulase
C. Papain
D. Lipase
22. Allosteric regulation is a crucial mechanism for controlling enzyme activity. What is the hallmark of allosteric regulation?
A. Substrate binding directly to the active site.
B. Regulation by molecules binding at a site other than the active site.
C. Regulation only by irreversible inhibitors.
D. Regulation solely through changes in temperature.
23. Hydrolases are enzymes that catalyze hydrolysis reactions. What is the general reaction catalyzed by hydrolases?
A. Joining two molecules together.
B. Rearranging atoms within a molecule.
C. Breaking bonds by the addition of water.
D. Transferring functional groups between molecules.
24. Statins are a class of drugs used to lower cholesterol levels. They function by inhibiting an enzyme involved in cholesterol biosynthesis. Which enzyme is the target of statin drugs?
A. HMG-CoA reductase
B. Cholesterol esterase
C. Lipoprotein lipase
D. Acyl-CoA cholesterol acyltransferase (ACAT)
25. Multienzyme complexes are assemblies of multiple enzymes that catalyze sequential reactions in a metabolic pathway. What is a PRIMARY benefit of organizing enzymes into multienzyme complexes?
A. To increase the diffusion rate of substrates between active sites.
B. To decrease the efficiency of product formation.
C. To enhance reaction rate and prevent accumulation of intermediates.
D. To reduce the overall amount of enzyme protein needed in the cell.
26. The active site of an enzyme is crucial for its function. What is the PRIMARY role of the active site in enzyme catalysis?
A. To provide structural support to the enzyme.
B. To bind cofactors necessary for enzyme activity.
C. To provide a specific environment for substrate binding and catalysis.
D. To regulate the overall rate of enzyme production in the cell.
27. Enzyme inhibitors are molecules that reduce or prevent enzyme activity. Competitive inhibitors primarily affect which kinetic parameter?
A. Vmax only.
B. Km only.
C. Both Vmax and Km.
D. Neither Vmax nor Km.
28. Ligases or synthetases catalyze the formation of new bonds, often coupled with ATP hydrolysis. What type of bonds are commonly formed by ligases?
A. Peptide bonds only.
B. Glycosidic bonds only.
C. Carbon-carbon, carbon-oxygen, carbon-nitrogen, and carbon-sulfur bonds.
D. Hydrogen bonds only.
29. In the detergent industry, enzymes are added to laundry detergents to improve their cleaning power. Which type of enzyme is commonly used to remove protein stains?
A. Amylases
B. Lipases
C. Proteases
D. Cellulases
30. The Michaelis-Menten equation describes the relationship between reaction rate and substrate concentration for many enzymes. What does the Michaelis constant (Km) represent in this equation?
A. The maximum reaction rate when the enzyme is saturated with substrate.
B. The substrate concentration at which the reaction rate is half of Vmax.
C. The rate constant for the breakdown of the enzyme-substrate complex.
D. The equilibrium constant for substrate binding to the enzyme.
