Calculate the number of ATPS generated from the metabolic oxi- dation of the four carbons of acetoacetyl-CoA to CO,. Now consider the homolog derived from oxidation of an odd-numbered carbon chain, namely propionoacetyl-CoA. Calculate the net ATP yield from oxidation of the five carbons of this compound to CO,.
The oxidation of fatty acyl-CoA occurs inside the mitochondrial matrix through the sequence of four biochemical reactions involving dehydrogenation, hydration, dehydrogenation, and thiolysis and these reactions are collectively called as -oxidation. This -oxidation keeps on operating until the fatty acyl-CoA chain is broken down up to the level of acetyl CoA which enters the Krebs cycle for final oxidation to generate energy.
The aceto-acetyl CoA is the four carbon even numbered fatty acyl-CoA. So, aceto-acetyl CoA will undergo 1 cycle of beta oxidation to produce two acetyl-CoA molecules which will enter Krebs cycle to generate energy.
In Beta-Oxidation, 1 molecule of FADH2 and 1 molecule of NADH is also produced during the course of four sequential reactions which will get completely oxidized in oxidative phosphorylation to yield ATP. The end products are two molecules of acetyl-CoA which will enter Krebs cycle.
Total ATP from -oxidation of Aceto-acetyl CoA=ATP from NADH+ATP from FADH2
And, 1 molecule of NADH in oxidative phosphorylation=2.5 ATP
1 molecule of FADH2 in oxidative phosphorylation=1.5 ATP
Total ATP from -oxidation of Aceto-acetyl CoA=(2.5+1.5) ATP=4 ATP
In Krebs cycle, 1 acetyl-CoA is metabolized to 3 molecules of NADH, 1 molecule of FADH2, and 1 molecule of ATP.
Total ATP from Krebs cycle of 2 Acetyl CoA= ATP from NADH+ATP from FADH2+ ATP
1 molecule of NADH in oxidative phosphorylation=2.5 ATP
So, 6 molecules of NADH in oxidative phosphorylation=15 ATP
1 molecule of FADH2 in oxidative phosphorylation=1.5 ATP
So, 2 molecules of FADH2 in oxidative phosphorylation=3 ATP
Total ATP from Krebs cycle of 2 Acetyl CoA=(15+3+2) ATP=20 ATP
Therefore, total ATP generated from metabolic oxidation of four carbons of aceto-acetyl CoA=Total ATP from -oxidation of Aceto-acetyl CoA + Total ATP from Krebs cycle of 2 Acetyl CoA = (4+20) ATP= 24 ATP.
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