Principles of Biochemistry, Volume 2 - A. Lehninger 1985
Bioenergetics and Metabolism
Fatty Acid Oxidation in Animal Tissues
In the second stage of fatty acid oxidation, acetyl-CoA is oxidized via the citric acid cycle
The acetyl-CoA formed during Fatty acid oxidation is identical to that derived from Pyruvate. Its acetyl group is ultimately oxidized to CO2 and H2O via the same pathway, namely The Citric Acid Cycle (Fig. 16-1). The equation below represents the balance of the Second Stage of fatty acid oxidation (Fig. 18-5) for The oxidation of eight acetyl-CoA molecules derived from palmitoyl-CoA, coupled with Oxidative Phosphorylation:
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Combining equations (4) and (5) for the First and Second stages of fatty acid oxidation gives the overall equation for the Complete oxidation of palmitoyl-CoA to carbon dioxide and Water:
Table 18-1. ATP yield at individual oxidation steps during the oxidation of one molecule of palmitoyl-CoA to CO2 and H2O
|
Enzyme catalyzing the reaction |
NAD-dependent steps |
FAD-dependent steps |
Number of ATP molecules |
|
Acyl-CoA dehydrogenase |
7 |
14 |
|
|
3-hydroxyacyl-CoA dehydrogenase |
7 |
21 |
|
|
Isocitrate dehydrogenase |
8 |
24 |
|
|
α-Ketoglutarate dehydrogenase |
8 |
24 |
|
|
Succinyl-CoA synthetase1) |
8 |
||
|
Succinate dehydrogenase |
8 |
16 |
|
|
Malate dehydrogenase |
8 |
24 |
|
|
Total |
131 |
1) Assuming that the GTP formed reacts with ADP to yield ATP
Table 18-1 shows the yield of NADH, FADH2, and ATP at various stages of fatty acid oxidation. The standard free-energy change for the oxidation of palmitic acid to CO2 and H2O is approximately 2340 kcal/mol. Under standard conditions, 7.3 × 131 = 956 kcal of this amount is conserved as ATP phosphate bond energy. However, when free-energy changes are calculated based on the actual intracellular concentrations of reactants and products, over 80% of the released Free energy is conserved as the phosphate-bond energy of ATP.
Last update: 06/08/2026
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