Question

Choose the incorrect statements:

I. Electrons from NADH produced in the mitochondrial matrix are oxidized by complex II
II. Ubiquinones oxidised to ubiquinol by receiving reducing equivalents from complex I
III. Ubiquinol oxidized to ubiquinone by transfer of electrons to complex III

• A. I and II
• B. II and III
• C. I and III
• D. III only

Hint:

NADH uses Complex I for oxidation; Ubiquinone is reduced (not oxidized) when it accepts electrons.

Answer 1

The Correct Option is A

Statement I: Incorrect — Electrons from NADH are oxidized by Complex I (not Complex II).
Statement II: Incorrect — Ubiquinone (Q) is reduced to ubiquinol (QH$_2$), not oxidised, by receiving electrons.
Statement III: Correct — Ubiquinol transfers electrons to Complex III and becomes oxidized to ubiquinone.