Question 14:
In cytosol, the product yield from the oxidation of one molecule of glucose is:
Glycolysis Cytosol Glucose Oxidation Yield
Glycolysis occurs in the cytosol and breaks down one glucose molecule into two pyruvates. The correct product yield is option (A).
Correct Answer
(A) 2 pyruvate + 2 NADH + 2 ATP
This matches the net products from glycolysis, the only oxidation pathway fully in the cytosol.
Glycolysis Overview
Glycolysis converts glucose (C6H12O6) to two pyruvate molecules through 10 enzyme-catalyzed steps. It yields a net gain of 2 ATP via substrate-level phosphorylation and 2 NADH from NAD+ reduction. No further oxidation occurs in cytosol; pyruvate enters mitochondria next.
Option Analysis
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(A) 2 pyruvate + 2 NADH + 2 ATP: Correct. Glucose splits into two 3-carbon pyruvates; 4 ATP produced minus 2 consumed gives net 2 ATP; glyceraldehyde-3-phosphate dehydrogenase generates 2 NADH.
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(B) 2 pyruvate + 1 NADH + 2 ATP: Incorrect. Underestimates NADH; both glycolytic triose phosphates produce NADH, totaling 2 per glucose.
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(C) 1 pyruvate + 2 NADH + 2 ATP: Incorrect. One glucose always yields 2 pyruvates via symmetrical cleavage at aldolase step.
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(D) 1 pyruvate + 1 NADH + 2 ATP: Incorrect. Wrong on both pyruvate (should be 2) and NADH (should be 2) counts.
| Option | Pyruvate | NADH | ATP | Status |
|---|---|---|---|---|
| A | 2 | 2 | 2 | Correct |
| B | 2 | 1 | 2 | Wrong NADH |
| C | 1 | 2 | 2 | Wrong pyruvate |
| D | 1 | 1 | 2 | Both wrong |
Exam Preparation Tips
Focus on net yields: investment phase (2 ATP used), payoff phase (4 ATP, 2 NADH gained). Common errors stem from gross vs. net ATP or confusing with full respiration (30-38 ATP total).
