Answer to Question #87037 in Biochemistry for Arun Rawat

Question

b) How is the conversion of fatty acid to acyl - CoA accomplished thermodynamically? Explain giving the reactions involved.

Answer 1

For the calculation of the energy balance of degradation of fatty acid, a palmitic acid (16:0), which is completely oxidized to 16 CO₂ molecules can be used as an example. In the first stage, the fatty acid is activated by consuming two energy-rich linkages of ATP with the formation of palmitoyl-CoA consisting of eight C2 units. Then seven cycles of β-oxidation proceed. At the same time, 7 molecules of the reduced form of FADH₂ and 7 NADH H⁺ molecules are produced. Both compounds are included in the respiratory chain. The oxidation FADH₂ results in a total of 1.5 molecules of ATP while NADH H⁺ gives 2.5 molecules. As a result, β-oxidation of one palmitoyl residue yields 28 molecules of ATP. The oxidation of each molecule of acetyl-CoA causes the formation of 10 molecules of ATP accompanied by the formation of 80 molecules of ATP. However, two ATP molecules are consumed for the activation of palmitic acid during the initial step of oxidation. Therefore, oxidation of one molecule of palmitic acid leads to the synthesis of 106 molecules of ATP corresponding to free energy of 3300 kJ/mol (10⁶×30.5 kJ/mol ATP).