AQA A-Level Biology 2025/6

Biology • A-Level

Question 1 of 40

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In one complete turn of the Krebs cycle, which statement correctly links decarboxylation, dehydrogenation, and the reduced coenzyme that is formed?

Hint: Recall which steps of the cycle release CO₂ and what coenzyme they reduce.

Decarboxylation occurs only after succinyl‑CoA has been formed. Each decarboxylation step is accompanied by the reduction of NAD⁺ to NADH. Only the step that produces FADH₂ involves a decarboxylation. The reduction of NAD⁺ to NADH takes place without any carbon atoms being released as CO₂.

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