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

Cyanide binds the heme iron of Complex IV and blocks electron transfer to oxygen. What follows most directly in an exposed cell?

A.Electron flow through the chain backs up, proton pumping ceases, and chemiosmotic ATP production collapses.
B.Glycolysis stops immediately because its NAD+ pool is instantly destroyed.
C.The Krebs cycle accelerates enough to compensate and restore normal ATP output.
D.Proton pumping continues at Complex III using fermentation products as electron donors.

Explanation

Core Concept

Complex IV passes electrons to oxygen, the chain's terminal acceptor, while pumping protons across the inner membrane. Blocking it stalls the downstream handoff, so upstream complexes stay loaded and stop pumping. With the proton-motive force decaying, ATP synthase loses its driving gradient. The cell must then lean on glycolysis and fermentation for ATP.

Correct Answer

AElectron flow through the chain backs up, proton pumping ceases, and chemiosmotic ATP production collapses.

More Unit 3: Cellular Energetics practice questions

Try a random question →

Practice more AP Biology questions with full explanations

Practice Unit 3: Cellular Energetics Questions →