MCAT Biochemistry Question 21: Answer and Explanation

Home > MCAT Test > MCAT biochemistry practice tests

Test Information

Question: 21

6. In the equation below, substrate C is an allosteric inhibitor to enzyme 1. Which of the following is another mechanism necessarily caused by substrate C?

  • A. Competitive inhibition
  • B. Irreversible inhibition
  • C. Feedback enhancement
  • D. Negative feedback

Correct Answer: D

Explanation:

By limiting the activity of enzyme 1, the rest of the pathway is slowed, which is the definition of negative feedback. Choice (A) is incorrect because there is no competition for the active site with allosteric interactions. While many products do indeed competitively inhibit an enzyme in the pathway that creates them, this is an example of an allosterically inhibited enzyme. There is not enough information for choice (B) to be correct because we aren’t told whether the inhibition is reversible. In general, allosteric interactions are temporary. Choice (C) is incorrect because it is the opposite of what occurs when enzyme 1 activity is reduced.

Previous       Next