Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologyhardmcq1 pt

The uncoupler dinitrophenol (DNP) ferries protons across the inner mitochondrial membrane, bypassing ATP synthase. What best describes the result?

A.Electron transport and oxygen consumption continue or rise, but most captured energy leaves as heat instead of ATP
B.Both electron flow and oxygen use stop because no gradient can ever form
C.ATP output climbs because protons now enter the matrix through extra routes
D.The Krebs cycle shuts down immediately because NADH can no longer be oxidized

Explanation

Core Concept

Because DNP short-circuits the proton gradient, ATP synthase loses access to the proton-motive force even while the chain keeps pumping. NADH oxidation proceeds briskly and breathing accelerates as the body tries to compensate. The freed redox energy dissipates as heat, which made DNP dangerous as a weight-loss drug. Uncoupling thereby separates electron traffic from ATP manufacturing entirely.

Correct Answer

AElectron transport and oxygen consumption continue or rise, but most captured energy leaves as heat instead of ATP

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