How many molecules of NADH are produced from one molecule of glucose that undergoes glycolysis, the linking step, and 2 turns of the Krebs cycle? Select one: a. 2 b. 4 c. 0 d. 10
The correct answer and explanation is:
Correct Answer: d. 10
Explanation:
When one molecule of glucose is completely oxidized through glycolysis, the linking step, and two turns of the Krebs cycle, a total of 10 molecules of NADH are produced. Here’s the breakdown:
1. Glycolysis (Occurs in the cytoplasm):
- 1 glucose → 2 pyruvate
- Each glucose yields:
- 2 NADH
2. Linking Step (Pyruvate to Acetyl-CoA, in the mitochondria):
- Each pyruvate (2 total) is converted to 1 Acetyl-CoA, producing 1 NADH per pyruvate.
- So for 2 pyruvate:
- 2 NADH
3. Krebs Cycle (a.k.a. Citric Acid Cycle or TCA Cycle):
- Each Acetyl-CoA enters the cycle once. Since we have 2 Acetyl-CoA from 1 glucose, the cycle runs twice.
- Each turn of the Krebs cycle produces:
- 3 NADH
- Two turns produce:
- 3 NADH × 2 = 6 NADH
Total NADH molecules from one glucose:
- Glycolysis: 2 NADH
- Linking step: 2 NADH
- Krebs cycle: 6 NADH
- Total: 2 + 2 + 6 = 10 NADH
Conclusion:
These 10 NADH molecules are crucial because they carry high-energy electrons to the electron transport chain (ETC) in the mitochondria, where ATP is ultimately synthesized through oxidative phosphorylation. Thus, option d (10) is the correct answer.