What coenzymes are reduced during the Citric Acid Cycle?

The correct answer is based on the roles of the specific coenzymes in the Citric Acid Cycle, also known as the Krebs cycle. During this cycle, NAD+ and FAD serve as essential electron carriers that are involved in the oxidation of acetyl-CoA and other intermediates.

As the cycle progresses, NAD+ is reduced to NADH at several key steps. For example, it is reduced during the conversion of isocitrate to α-ketoglutarate and from α-ketoglutarate to succinyl-CoA. Similarly, FAD is reduced to FADH2 during the conversion of succinate to fumarate. Both NADH and FADH2 then proceed to the electron transport chain, where they play crucial roles in ATP production through oxidative phosphorylation.

The other coenzymes mentioned in the options do not participate in similar redox reactions within the cycle. For instance, Coenzyme A primarily acts as a carrier for acyl groups but is not reduced in the process. Similarly, ATP and GTP are energy-carrying molecules rather than electron carriers and are generated during substrate-level phosphorylation, not reduced. ADP functions in energy transfer but does not undergo reduction during the cycle. Therefore, the reduction of