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

Oxidation of FADH2 yields fewer ATP than oxidation of NADH because FADH2's electrons...

A.enter the transport chain at complex II, bypassing the proton pump at complex I
B.carry too little energy and reverse backward through complex IV into the matrix
C.are donated straight to oxygen without passing through any complexes
D.pump protons across the outer mitochondrial membrane instead

Explanation

Core Concept

Succinate dehydrogenase, which feeds FADH2's electrons onward, doubles as complex II of the respiratory chain. Because electrons enter below complex I, they pass only two pumping stations instead of three before reaching oxygen. Fewer protons are therefore moved into the intermembrane space, producing a smaller gradient and roughly 1.5 ATP equivalents instead of about 2.5 per carrier pair.

Correct Answer

Aenter the transport chain at complex II, bypassing the proton pump at complex I

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 →