Before entering the Krebs cycle, the pyruvate is first decarboxylated and oxidized into:
Correct answer: A. Acetyl-CoA
- A. Acetyl-CoA
- B. Oxaloacetate
- C. Lactic acid
- D. Citric acid
Explanation
Before entering the Krebs cycle, pyruvate is decarboxylated and oxidized into acetyl-CoA by the pyruvate dehydrogenase complex. This reaction releases one molecule of CO₂ and generates NADH. The acetyl-CoA formed then enters the Krebs cycle to combine with oxaloacetate, forming citric acid. Other options like oxaloacetate, lactic acid, and citric acid are related to cellular respiration but occur at different stages or under different conditions. Thus, the correct answer is Acetyl-CoA.
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About Bioenergetics
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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