Enzyme Kinetics MCAT Practice Question
A competitive inhibitor of lactate dehydrogenase is added to a reaction mixture containing enzyme and substrate. The inhibitor binds reversibly to the enzyme's active site with high affinity. When the substrate concentration is increased tenfold, the reaction velocity approaches the original uninhibited rate. What does this observation reveal about the mechanism of competitive inhibition and enzyme kinetics?
Answer choices
- AThe inhibitor has permanently denatured the enzyme active site.
- BIncreasing substrate concentration can overcome competitive inhibition by shifting equilibrium toward enzyme-substrate complex formation.
- CThe inhibitor binds irreversibly and cannot be displaced by excess substrate.
- DCompetitive inhibitors increase Km but do not change Vmax; excess substrate outcompetes the inhibitor for binding.Correct answer
- EThe enzyme exhibits cooperativity and requires multiple substrate molecules for activation.
- FExcess substrate decreases velocity in competitive inhibition
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