This document discusses how much ATP is generated from the oxidation of fatty acids. It explains that the number of ATP generated equals the number from the citric acid cycle plus those from reduced coenzymes during fatty acid oxidation. Each acetyl-SCoA that enters the citric acid cycle generates 10 ATP, and there are as many acetyl-SCoA molecules as half the number of carbon atoms in the fatty acid. An example of a 12-carbon fatty acid generating 78 ATP is provided to illustrate the calculations.

1. ENERGY FROM
FATTY ACID
OXIDATION

2. 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.

3. 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.

4. 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 ATP
Acetyl-SCoA
Activation of fatty acid: = -2 ATP
From the 5 B-oxidations:
4ATP x 5 B-oxidations = 20 ATP
B-oxidation
TOTAL= 78 ATP