Coenzyme Q is oxidized by which enzyme?
Correct answer: C. Complex III (Cytochrome bc1 complex)
- A. Cytochrome c oxidase
- B. Complex I (NADH: ubiquinone oxidoreductase)
- C. Complex III (Cytochrome bc1 complex)
- D. Complex IV (Cytochrome c oxidase)
Explanation
Coenzyme Q, or ubiquinone, plays a crucial role in the electron transport chain. It receives electrons from both Complex I and Complex II, becoming reduced to ubiquinol. The oxidation of ubiquinol back to ubiquinone occurs at Complex III, also known as the cytochrome bc1 complex, which then transfers the electrons to cytochrome c. This step is vital for maintaining the electron flow and building the proton gradient necessary for ATP synthesis. Options A and D describe complexes involved in later steps of the electron transport chain that do not directly oxidise Coenzyme Q. Option B describes a complex that reduces, not oxidises, Coenzyme Q.
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