MCAT Biochemistry Question 137: Answer and Explanation

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Question: 137

2. A patient has been exposed to a toxic compound that increases the permeability of mitochondrial membranes to protons. Which of the following metabolic changes would be expected in this patient?

A. Increased ATP levels
B. Increased oxygen utilization
C. Increased ATP synthase activity
D. Decreased pyruvate dehydrogenase activity

Correct Answer: B

Explanation:

The increased permeability of the inner mitochondrial membrane allows the proton-motive force to be dissipated through locations besides the F₀ portion of ATP synthase. Therefore, ATP synthase is less active and is forming less ATP, invalidating choices (A) and (C). The body will attempt to regenerate the proton-motive force by increasing fuel catabolism, eliminating choice (D). This increase in fuel use requires more oxygen utilization in the electron transport chain.

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