Question

Ketone bodies are synthesized when__________________.

	A.	The amount of liver citrate exceeds the amount need to generate ATP
	B.	The amount of liver oxaloacetate exceeds the amount of acetyl-coA needed for the citric acid cycle.
	C.	The amount of liver acetyl-coA exceeds the amount of available oxaloacetate.
	D.	The amount of free liver NAD+ exceeds the amount required by the citric acid cycle.

Answer 1

Ans:

C. The amount of liver acetyl-coA exceeds the amount of available oxaloacetate.

Explanation: In normal conditions, fatty acids oxidation produces acetyl-CoA which is used by citric acid cycle or in fatty acid synthesis, so, small amount of excess acetyl-CoA are present. In mitochondria of liver, when the acetyl-CoA exceeds to its citric acid cycle intermediates (like citrate,oxaloacetate etc.), it leads to the formation of ketone bodies. The acetyl-CoA are produced three ketone bodies, namely acetoacetate, -hydroxybutyrate acetone by a process called ketogenesis. During ketone bodies synthesis, the concentration of citrate or oxaloacetate or NAD+ are low in comparison to acetyl-CoA.