In beta-oxidation of palmitoyl-CoA, how many cycles occur and what are the products?

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Multiple Choice

In beta-oxidation of palmitoyl-CoA, how many cycles occur and what are the products?

In beta-oxidation, the fatty acyl-CoA is shortened by two carbons each cycle, producing one acetyl-CoA plus one FADH2 and one NADH, until the chain is completely converted to acetyl-CoA units. For palmitoyl-CoA (a 16-carbon fatty acid), you can remove two carbons seven times, giving eight acetyl-CoA molecules in total and generating seven FADH2 and seven NADH across those cycles. The activation step to form palmitoyl-CoA from palmitate uses two ATP equivalents before beta-oxidation begins. Now count the energy: the eight acetyl-CoA molecules each yield about 10 ATP when fully oxidized in the TCA cycle and oxidative phosphorylation, totaling 80 ATP. The seven NADH produced contribute about 7 × 2.5 = 17.5 ATP, and the seven FADH2 contribute about 7 × 1.5 = 10.5 ATP. Adding those together gives 80 + 17.5 + 10.5 = 108 ATP. Subtract the two ATP paid for activation, leaving a net of 106 ATP. That matches the described result.

In beta-oxidation, the fatty acyl-CoA is shortened by two carbons each cycle, producing one acetyl-CoA plus one FADH2 and one NADH, until the chain is completely converted to acetyl-CoA units. For palmitoyl-CoA (a 16-carbon fatty acid), you can remove two carbons seven times, giving eight acetyl-CoA molecules in total and generating seven FADH2 and seven NADH across those cycles. The activation step to form palmitoyl-CoA from palmitate uses two ATP equivalents before beta-oxidation begins.

Now count the energy: the eight acetyl-CoA molecules each yield about 10 ATP when fully oxidized in the TCA cycle and oxidative phosphorylation, totaling 80 ATP. The seven NADH produced contribute about 7 × 2.5 = 17.5 ATP, and the seven FADH2 contribute about 7 × 1.5 = 10.5 ATP. Adding those together gives 80 + 17.5 + 10.5 = 108 ATP. Subtract the two ATP paid for activation, leaving a net of 106 ATP. That matches the described result.

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