During the conversion of α-ketoglutarate to oxaloacetate, how many molecules of reduced electron carrier are generated?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (C)

The conversion of α-ketoglutarate to oxaloacetate occurs through the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, which is critical in cellular respiration. In the context of this reaction, it’s important to understand the specific steps involved and how electron carriers are produced.

Initially, α-ketoglutarate undergoes a transformation where it is decarboxylated, resulting in succinyl-CoA while releasing carbon dioxide. This reaction is catalyzed by the α-ketoglutarate dehydrogenase complex, which is similar in functionality to the pyruvate dehydrogenase complex. During this decarboxylation, NAD+ is reduced to NADH. This process generates one molecule of NADH, contributing to the electron transport chain.

As the cycle continues, succinyl-CoA is converted into succinate, which involves the substrate-level phosphorylation that produces GTP or ATP. Subsequently, succinate is oxidized to fumarate, leading to the reduction of another molecule of FAD to FADH2.

Following these steps, fumarate is then further converted to malate and subsequently to oxaloacetate. In the malate to ox