Approximately how many ATP molecules are generated from the complete oxidation of a fatty acid such as palmitate?

• A. 60
• B. 106
• C. 90
• D. 120

Answer: (B)

Fatty acids pack a lot of energy because their carbons are chopped into many acetyl-CoA units and each round of beta-oxidation also liberates reducing equivalents that feed the electron transport chain.

Palmitate has 16 carbons, so it yields 8 acetyl-CoA units when fully oxidized. It goes through 7 rounds of beta-oxidation, producing 7 NADH and 7 FADH2. Each acetyl-CoA then enters the TCA cycle, giving 3 NADH, 1 FADH2, and 1 GTP per acetyl-CoA. For 8 acetyl-CoA, that’s 24 NADH, 8 FADH2, and 8 GTP (ATP).

Converting these to ATP with typical yields (NADH ≈ 2.5 ATP, FADH2 ≈ 1.5 ATP, and 1 GTP ≈ 1 ATP): beta-oxidation contributes 7 NADH (17.5 ATP) plus 7 FADH2 (10.5 ATP) = 28 ATP. TCA for all acetyl-CoA contributes 24 NADH (60 ATP) + 8 FADH2 (12 ATP) + 8 ATP from GTP = 80 ATP. Together that’s about 108 ATP, but activating palmitate to palmitoyl-CoA costs 2 ATP equivalents, bringing the net yield to approximately 106 ATP.

So, the best answer is about 106 ATP.