Let\'s do a bit of ATP accounting. This will be for arachidonic acid. This fatty

Question

Let's do a bit of ATP accounting. This will be for arachidonic acid. This fatty acid has 20 C atoms and 4 C=C double bonds.

NOTE: The presence of a double bond eliminates the need for FADH2 in one cycle of the beta-oxidation pathway, thus reducing ATP production by 1.5.

How many ATP equivalents are produced from the complete aerobic catabolism of arachidonic acid -- you'll have to do a calculation to get the answer. Remember to use 1.5 ATP produced per FADH2 and 2.5 ATP produced per NADH in oxphos.

It simplifies the calculation to remember that 10 ATP equivalents are produced in the processing of 1acetylCoA (through the CAC and oxidative phosphorylation).

Explanation / Answer

Since arachidonic acid has 20 carbons, it undergoes 9 cycles of beta oxidation. 9 cycles give 10 acetyl CoA molecules. As given in the question, one acetyl CoA gives 10 ATP molecules.

During beta oxidation, 9 NADH and 9 FADH2 are produced.

So the total number of ATP would be:

10 acetyl-CoA gives 100 ATP

9 NADH gives 22.5 ATP

9 FADH2 gives 13.5 ATP

This gives a total of 136 ATP (100 moles of ATP from Acetyl Co A, 22.5 moles of ATP from NADH, and 13.5 moles of ATP from FADH2)

Removing 2 ATP for the process of activation would give 134 ATP.

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