Enzymes MCQs (Quiz 11)By guishaqasif / April 29, 2026 1. Which statement best distinguishes enzyme repression from enzyme induction? Induction is irreversible Both processes decrease enzyme activity Both processes increase enzyme synthesis Repression decreases while induction increases enzyme synthesis 2. Lyases differ from hydrolases because they _______ Transfer electrons between molecules Use ATP to form covalent bonds Break chemical bonds without the involvement of water Require cofactors for all reactions 3. Isomerases are enzymes that catalyze _______ Oxidation–reduction (redox) reactions Cleavage of chemical bonds Transfer of functional groups between molecules Intramolecular rearrangements of atoms within a molecule 4. Which statement best describes enzyme action? Enzymes provide an alternative reaction pathway Enzymes change ΔG of reaction Enzymes alter equilibrium constant Enzymes increase product stability 5. The lock-and-key model of enzyme action assumes that _______ The product binds to the enzyme before the substrate The active site is rigid and already complementary to the substrate The substrate induces a conformational change in the enzyme he enzyme structure is highly flexible and changes shape upon substrate binding 6. The induced-fit model improves upon the lock-and-key model by emphasizing _______ Rigid binding between enzyme and substrate Destruction of the enzyme during catalysis Irreversible binding of substrate to enzyme Dynamic conformational changes in the enzyme upon substrate binding 7. The specificity of an enzyme is primarily determined by _______ Shape and chemical properties of the active site Temperature Reaction velocity Substrate concentration 8. Enzymes are best described as _______ Biological catalysts that lower activation energy Energy-rich compounds Substances that increase reaction equilibrium Molecules consumed during reactions 9. Feedback repression in metabolic pathways is an example of _______ Positive regulation enhancing gene expression Irreversible inhibition of enzyme activity Negative regulation reducing gene transcription Covalent regulation via phosphorylation 10. Hydrolases are enzymes that catalyze _______ Hydrolysis reactions involving cleavage of bonds using water Transfer of functional groups between molecules Formation of covalent bonds using ATP Oxidation–reduction reactions involving electron transfer Loading … Question 1 of 10
