Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologymediummcq1 pt

A drug makes the inner mitochondrial membrane leaky to protons. In cells exposed to this drug, which outcome is expected?

A.Electron transport continues, but ATP synthesis drops sharply because the proton gradient dissipates before driving ATP synthase.
B.Electron transport halts entirely because NADH can no longer deposit electrons at Complex I.
C.ATP output rises because protons reach the matrix more quickly than normal.
D.Oxygen consumption stops while ATP production continues at normal rates.

Explanation

Core Concept

An uncoupler short-circuits the gradient: protons re-enter the matrix without passing through ATP synthase. Electron transport keeps pumping, so oxygen consumption may even rise, but little free energy stays stored in the gradient to make ATP. The lost energy escapes mainly as heat, which is why uncoupling agents raise body temperature dangerously.

Correct Answer

AElectron transport continues, but ATP synthesis drops sharply because the proton gradient dissipates before driving ATP synthase.

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