Question

How many ATP will be made from a 13:0 lipid? Also what is the difference between odd numbered fatty acids and even numbered fatty acids in terms of how they're broken down? How many rounds of Beta oxidation will it undergo, what are the products, and how do you determine this? Last thing, how many rounds of the citric acid cycle are run?

Answer 1

Considering an average production of 2.5 ATP/NADH and 1.5 ATP/FADH2 using the respiratory chain, you have 108 ATP molecules. However, 2 ATP molecules were consumed during the initial activation of Palmitate to Palmitoyl-CoA which is going to be oxidized in the mitochondria. So, net energy output = (108 - 2) = 106 ATP.

Fatty acid degradation. Fatty acid degradation is the process in which fatty acids are broken down into their metabolites, in the end generating acetyl-CoA, the entry molecule for the citric acid cycle, the main energy supply of animals. It includes three major steps: Lipolysis of and release from adipose tissue.

Fatty acids having an odd number of carbon atoms are minor species. They are oxidized in the same way as fatty acids having an even number, except that propionyl CoA and acetyl CoA, rather than two molecules of acetyl CoA, are produced in the final round of degradation.

For 16 carbon FA: 7 rounds of beta oxidation, produce 8 acetyl CoA. 7 rounds because the 7th round splits the last 4 carbons.

In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH₂, which are co-enzymes used in the electron transport .

Beta-oxidation

Beta-oxidation consists of four steps:

1) Dehydrogenation catalyzed by acyl-CoA dehydrogenase, which removes two hydrogens between carbons 2 and 3.

2) Hydration catalyzed by enoyl-CoA hydratase, which adds water across the double bond.

3) Dehydrogenation catalyzed by 3-hydroxyacyl-CoA dehydrogenase, which generates NADH.

4) Thiolytic cleavage catalyzed beta-ketothiolase, which cleaves the terminal acetyl-CoA group and forms a new acyl-CoA which is two carbons shorter than the previous one.

The shortened acyl-CoA then reenters the beta-oxidation pathway.

Dehydrogenation

This step uses FAD and produces FADH2, which will enter the citric acid cycle and form ATP to be used as energy

Oxidation

The end products are β-ketoacyl CoA and NADH + H. NADH will enter the citric acid cycle and produce ATP that will be used as energy.

End of Beta Oxidation

Another chemical reaction then converts propionyl-CoA to succinyl-CoA (see the figure below), which enters the citric acid cycle to produce ATP.

3 rounds of citric acid cycle are run