Which of the following statements is incorrect?

Among the four statements, the one that is incorrect is:

“In ETC (Electron Transport Chain), one molecule of NADH + H⁺ gives rise to 2 ATP molecules, and one FADH₂ gives rise to 3 ATP molecules.”

This statement is wrong because the actual ATP yields from oxidative phosphorylation are not 2 ATP for NADH and 3 ATP for FADH₂. The correct yields, based on modern bioenergetics, are approximately:

• NADH (entered at Complex I) → about 2.5 ATP

• FADH₂ (entered at Complex II) → about 1.5 ATP

The difference arises from the number of protons pumped across the inner mitochondrial membrane. Each NADH oxidation results in the translocation of roughly 10 protons, while each FADH₂ oxidation moves about 6 protons.

$10 H+\Rightarrow \; 3 ATP$ (theoretical maximum, but because part of the proton motive force is used for other processes, the effective yield is ~2.5 ATP per NADH).
$6 H+\Rightarrow \; 3 ATP$ (theoretical maximum, giving an effective yield of ~1.5 ATP per FADH₂).

Therefore the claim that NADH produces only 2 ATP while FADH₂ produces 3 ATP reverses the actual relationship and overestimates the ATP from FADH₂. Hence, this statement is the incorrect one.