ENERGY FROM FATTY ACID OXIDATION

In the case of fatty acids, this the total number of ATP from passage of acetyl-SCoA through the citric acid cycle plus those produced by the reduced coenzyme (NADH and FADH2) during fatty acid oxidation.

First, we need to know the number of molecules of acetyl-SCoA from the fatty acids, since two carbon atoms are removed w/ each acetyl-SCoA, the total number of acetyl-SCoA for a fatty acid is its number of carbon atoms divided by 2.

These acetyl-SCoA proceed to the citric acid cycle, where each one yield 1 ATP and a total of 3 ADH and 1 FADH2.

Using the current best estimates of 2.5 ATP for each NADH and 1.5 ATP for each FADH2, each acetyl-SCoA generates 9 ATP from reduced coenzymes, giving a total of 10 ATP per acetyl-SCoA.

In addition, we must take into account t umber of ATP derived from the two reduced coenzymes (1 FADH2 ad NADH) from each repetition of B-oxidation. With 1.5 ATP per FADH2 and 2.5 ATP per NADH, the is 4 ATP for each B-oxidation.

NOTE that the number of repetition is always one less than the number of acetyl-SCoA molecule produced. Also we must subtract the equivalent of 2 ATP spent in activation of a fatty acid, the step that precedes the B-oxidation.

EXAMPLE: 12-carbon fatty acid, lauric acid (CH3(CH2)10COOH yield 78 ATP From the citric acid cycle: 12C atoms/2 = 6 acetyl-SCoA

10 ATP x 6 acetyl-SCoA = 60 ATPAcetyl-SCoA Activation of fatty acid: = -2 ATP

From the 5 B-oxidations:

4ATP x 5 B-oxidations = 20 ATPB-oxidation

TOTAL= 78 ATP