Before the start of the Krebs cycle, the following changes occur, EXCEPT:
Correct answer: B. Oxidation of acetate
- A. Formation of acetyl-Co-A
- B. Oxidation of acetate
- C. Reduction of NAD
- D. Decarboxylation of pyruvate
Explanation
The correct answer is the oxidation of acetate. Before the Krebs cycle starts, pyruvate undergoes decarboxylation to form acetyl-CoA, and NAD⁺ is reduced to NADH in the process. These steps are crucial for linking glycolysis to the Krebs cycle. However, acetate itself is not oxidized prior to the Krebs cycle; instead, acetyl-CoA, which is derived from pyruvate, is the molecule that enters the cycle. Therefore, the oxidation of acetate is the exception to the processes listed.
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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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