Question

Describe the β-oxidation of the fatty acid palmitate.

biochem question

Answer 1

In the first stage of β oxidation, the fatty acids undergo oxidative removal of successive two carbon units in the form of acetyl-CoA, starting from the carboxyl end of the fatty acyl chain. For example, the 16-carbon fatty acid palmitic acid (palmitate at pH 7) undergoes seven cycles passes through this oxidative sequence, in each pass losing two carbons as acetyl-CoA. At the end of seven cycles the last two carbons of palmitate ( C-15 and C-16) are left as acetyl-CoA. The overall result is the conversion of the 16-carbon chain of palmitate to eight two-carbon acetyl-CoA molecules. Formation of each molecule of acetyl-CoA requires removal of four hydrogen atoms (two pairs of electrons and four H⁺) from the fatty acyl moiety by the action of dehydrogenases.

In the second stage of fatty acid oxidation, the acetyl residues of acetyl-CoA are oxidized to CO₂ through the citric acid cycle, which also takes place in the mitochondrial matrix. Acetyl-CoA derived from fatty acid oxidation thus enters a final common pathway of oxidation along with acetyl-CoA derived from glucose through glycolysis and pyruvate oxidation.

The first two stages of fatty acid oxidation produce the reduced electron carriers NADH and FADH₂, which in the third stage donate electrons to the mitochondrial respiratory chain through which the electrons are carried to oxygen. Coupled to this flow of electrons is the phosphorylation of ADP to ATP. Thus, energy released by fatty acid oxidation is conserved as ATP.

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