Which of the following is the correct sequence in the Krebs cycle?
Correct answer: D. Isocitric acid → α-Ketoglutaric acid → Succinic acid
- A. Isocitric acid → Oxalosuccinic acid → α-Ketoglutaric acid
- B. Oxalosuccinic acid → Isocitric acid → α-Ketoglutaric acid
- C. α-Ketoglutaric acid → Isocitric acid → Oxalosuccinic acid
- D. Isocitric acid → α-Ketoglutaric acid → Succinic acid
Explanation
In the Krebs cycle, the sequence of reactions involving the conversion of isocitric acid to α-ketoglutaric acid and then to succinic acid is crucial. Isocitric acid undergoes oxidative decarboxylation to form α-ketoglutaric acid. This is followed by another decarboxylation, producing succinyl-CoA, which is then converted to succinic acid. Understanding the order of these reactions helps in tracing the flow of carbon atoms and the generation of energy carriers like NADH and FADH2. Option A and B are incorrect because they suggest sequences that do not occur in the Krebs cycle. Option C suggests a reverse order that is not possible in the cycle's progression.
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Cellular respiration explains how cells release energy from glucose through glycolysis, the link reaction, Krebs cycle and electron transport chain. It includes ATP production, substrate-level and oxidative phosphorylation, aerobic versus anaerobic respiration, and the roles of mitochondria, oxygen and fermentation in energy transfer.
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