How many ATP molecules are generated from the complete aerobic oxidation of palmitoyl-CoA?

Question

BlackTom AI · Accepted Answer

Palmitoyl-CoA (16 carbons) undergoes seven rounds of beta-oxidation to yield eight acetyl-CoA. Each beta-oxidation cycle (except the final cleavage) produces 1 FADH2 and 1 NADH; each acetyl‑CoA entering the citric acid cycle yields 3 NADH, 1 FADH2, and 1 GTP (equivalent to 1 ATP). Using the commonly accepted oxidative phosphorylation yields (P/O): NADH = 2.5 ATP, FADH2 = 1.5 ATP, and GTP = 1 ATP:

1) Relevant knowledge points and concepts
- Number of beta-oxidation cycles = (n/2) − 1 = (16/2) − 1 = 8 − 1 = 7 cycles.
- Acetyl-CoA produced = n/2 = 8 acetyl-CoA.
- Per beta-oxidation cycle: 1 NADH and 1 FADH2.
- Per acetyl-CoA oxidized in TCA: 3 NADH, 1 FADH2, 1 GTP.
- Activation of free palmitate to palmitoyl‑CoA costs 2 ATP equivalents (ATP → AMP + PPi).

2) Complete reasoning and step-by-step calculation
- Electrons from beta-oxidation cycles:
  - NADH from beta-oxidation = 7 × 2.5 = 17.5 ATP
  - FADH2 from beta-oxidation = 7 × 1.5 = 10.5 ATP
- Oxidation of 8 acetyl‑CoA in TCA:
  - Per acetyl-CoA = (3 × 2.5) + (1 × 1.5) + 1 = 7.5 + 1.5 + 1 = 10 ATP
  - For 8 acetyl‑CoA = 8 × 10 = 80 ATP
- Sum before activation cost = 80 + 17.5 + 10.5 = 108 ATP
- Subtract activation cost (2 ATP equivalents): 108 − 2 = 106 ATP

3) Intermediate steps shown above (all multiplications and additions detailed).

4) Why the correct answer is correct
The 106 ATP total results from summing ATP equivalents produced during beta-oxidation and subsequent citric acid cycle oxidation, then subtracting the 2 ATP required to activate palmitate. This uses modern P/O ratios (NADH = 2.5, FADH2 = 1.5), which are standard for current biochemical accounting.

5) Why the other options are incorrect
- 108 molecules (option a) equals the gross yield before subtracting the 2 ATP activation cost, so it ignores activation energy.
- 98 and 96 molecules (options c and d) do not match calculations using standard P/O values; they likely reflect inconsistent P/O assumptions or arithmetic errors.

6) Conclusion
Therefore, the complete aerobic oxidation of palmitoyl‑CoA yields 106 ATP molecules, confirming the provided answer.

How many ATP molecules are generated from the complete aerobic oxidation of palmitoyl-CoA?单项选择题

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