Correct option is C
Succinate dehydrogenase is a key enzyme in the citric acid cycle (Krebs cycle), but it does not reduce NAD⁺. Instead, it reduces FAD to FADH₂ as it oxidizes succinate to fumarate. Other enzymes in the list, such as lactate dehydrogenase, pyruvate dehydrogenase, and isocitrate dehydrogenase, use NAD⁺ as the electron acceptor, reducing it to NADH in their respective catalytic reactions.
Information Booster:
1. Lactate dehydrogenase converts pyruvate to lactate, reducing NAD⁺ to NADH.
2. Pyruvate dehydrogenase oxidizes pyruvate, reducing NAD⁺ to NADH and producing acetyl-CoA.
3. Succinate dehydrogenase reduces FAD to FADH₂, bypassing NAD⁺ entirely.
4. Isocitrate dehydrogenase reduces NAD⁺ to NADH while converting isocitrate to α-ketoglutarate.
5. The distinction between NAD⁺ and FAD as electron acceptors is crucial for understanding cellular metabolism. NAD⁺ is a common electron acceptor for most dehydrogenases except SDH.
6. SDH reduces FAD, which has a different redox potential than NAD⁺.
7. Understanding enzyme specificity helps in identifying metabolic pathways.
Additional Knowledge:
Lactate dehydrogenase (LDH): Catalyzes the interconversion of pyruvate and lactate with simultaneous interconversion of NADH and NAD⁺. It plays a vital role in anaerobic glycolysis.
Pyruvate dehydrogenase (PDH): A multi-enzyme complex that converts pyruvate into acetyl-CoA in the mitochondria, producing NADH in the process. It links glycolysis to the citric acid cycle.
Succinate dehydrogenase (SDH): Unique as it functions in both the citric acid cycle and the electron transport chain (Complex II). It reduces FAD to FADH₂ and transfers electrons directly to the respiratory chain.
Isocitrate dehydrogenase (IDH): Exists in two forms, one using NAD⁺ and the other NADP⁺. It catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate, producing NADH/NADPH.
