[Campbell Biology P.224] Why does FADH2 contribute less energy for ATP synthesis compared to... | Practice Question

Why does FADH2 contribute less energy for ATP synthesis compared to NADH, despite both donating an equivalent number of electrons 2 for oxygen reduction?

  • A: FADH2 adds its electrons at a lower energy level within complex II, bypassing complex I, leading to fewer protons pumped.
  • B: NADH is more electronegative than FADH2, allowing it to donate electrons more efficiently.
  • C: FADH2 directly passes its electrons to oxygen without going through the entire electron transport chain.
  • D: NADH transports fewer protons across the membrane than FADH2.

Explanation

The text states: 'FADH2 adds its electrons from within complex II, at a lower energy level than NADH does.' Since it enters at a lower energy point, it bypasses some of the proton-pumping complexes that NADH passes through, resulting in fewer protons being pumped and thus less ATP synthesis.