Multiple choice

When one molecule of FADH2 is oxidised to FAD, the number of ATP produced is

  1. one

  2. two

  3. three

  4. four

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the electron transport chain, each FADH2 molecule yields approximately 1.5 to 2 ATP molecules (modern estimates use 1.5, older textbooks used 2). FADH2 enters the chain at Complex II (coenzyme Q), bypassing Complex I, so it pumps fewer protons and generates less ATP than NADH, which yields 2.5 to 3 ATP.

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