Question

Under conditions where ketone bodies are being produced in the liver, how many ATPs can be produced from a molecule of palmitic acid if all resulting molecules of acetyl-CoA are converted into β -hydroxybutyrate?

Answer 1

Ketone body is the product of fatty acid break down. It is produced when the body has a low intake of carbohydrates. Since they are water-soluble so they can be transported to the cell where they break down into acetyl Co-A and enter the TCA cycle.

One Cycle of Beta-oxidation produces one acetyl Co-A along with one NADH and one FADH.

It will take 6 cycles to produce six acetyl Co-A and the last cycle produce 2 acetlCo-A.

So overall 8 acetyl Co-A and 7 NADH and 7 FADH.

Two acetyl are joined to make β -hydroxybutyrate and one NADH is used for the reaction

So a total of four β -hydroxybutyrate is formed from one palmitic acid and four NADH are utilized.

So overall 7 FADH and 3 NADH are remaining after conversion of acetyl Co-A to β -hydroxybutyrate.

One FADH gives 1.5 ATP and one NADH gives 2.5 ATP.

So total ATP = 1.5*7 + 2.5 * 3 = 10.5 + 7.5 = 18ATP.