Enzymes MCQs (Quiz 9)By guishaqasif / April 29, 2026 1. Which cellular process is directly affected during enzyme repression? Transcription of genes encoding the enzyme Catalysis of biochemical reactions Protein folding into functional conformation Translation of mRNA into protein 2. Enzyme induction results in _______ Reduced synthesis of enzyme proteins Immediate activation of pre-existing enzymes Increased transcription of genes encoding the enzyme Denaturation of enzyme proteins 3. Which enzyme level is commonly elevated in alcoholism? Acid phosphatase Serum glutamate pyruvate transaminase (SGPT) Hepatitis Gamma-glutamyl transpeptidase (GGT) 4. Why is cyclooxygenase-1 (COX-1) important for human health? It is essential for DNA biosynthesis It helps produce hormones that protect the stomach lining It is a chemical derivative of aspirin It transports carbon dioxide in blood 5. The Michaelis constant (Km)) is defined as the substrate concentration at which __________________ Product inhibition begins to significantly reduce enzyme activity The reaction velocity equals half of the maximum velocity (1/2 Vmax) The enzyme achieves its maximum turnover number (kcat) All enzyme active sites are fully saturated with substrate 6. Tryptophan synthetase in E. coli is composed of _______ Two distinct protein subunits designated A (α) and B (β) Only protein A One protein A  with a single subunit Only protein B 7. Which regulatory mechanism is relatively slow but energy-efficient in controlling enzyme levels? Gene repression Allosteric regulation Covalent modification Substrate binding 8. An enzyme remains unchanged after a reaction because it _______ Is converted into product Acts as a catalyst without being used up Forms permanent complexes Is consumed slowly 9. In feedback repression, the end product of a biosynthetic pathway functions as _______ A substrate for the enzyme A corepressor that activates the repressor protein An inducer that activates gene expression A competitive inhibitor of the enzyme 10. Which factor primarily distinguishes enzyme repression from enzyme inhibition? Temperature of the reaction system Time scale of regulation Substrate concentration pH of the environment Loading …
