When NADH Is the Electron Donor to the Respiratory Chain

Multiple Choice

When NADH is the electron donor to the respiratory chain, 2.5 ATP are formed, but when FADH₂ is the electron donor, only 1.5 ATP are formed.This difference occurs because

A) complex I accepts electrons from both NADH and FADH₂ but donates the electrons to different sites on the complex, which produces a larger proton gradient for NADH.
B) complex I accepts electrons from NADH but not FADH₂, resulting in an extra step that allows a larger proton gradient to form.
C) complex II accepts electrons from both NADH and FADH₂ but donates the electrons to different sites on the complex, which produces a larger proton gradient for NADH.
D) energy, in the form of heat, is lost when FADH₂, but not NADH, is the electron donor, resulting in lower energy yield.
E) NADH interacts with ATP synthase more efficiently than FADH₂, resulting in more ATP production.