Question

Why may ketone bodies form in some patients?

A. lipids are not getting absorbed in the small intestine

B. glycolysis is stimulated in the liver

C. acetyl-CoA is converted into ketone bodies instead of continuing through the citric acid cycle

D. oxaloacetate is available for the citric acid cycle

E. proteins are not digested correctly

Answer 1

The acetyl CoA produced by fatty acid oxidation enters the citric acid cycle and is further oxidized. Some amount of it in liver mitochondria is used for the synthesis of a group of water soluble compounds known as ketone bodies. These include acetone, acetoacetate and beta Hydroxybutyric acid. They serve as fuel sources to a limited extent.

The acetyl CoA produced by various metabolic processes is further processed via Krebs cycle. But this happens only when the availability of oxaloacetate is sufficient which in turn is dependent on the carbohydrate metabolism. In conditions where carbohydrate is either unavailable (starvation) or underutilized (diabetes), oxaloacetate is unavailable for combining with acetyl CoA. Under such conditions acetyl CoA is diverted to form ketone bodies.

Option A: If lipids are not absorbed in small intestine then they will be excreted in faeces. This condition is called steatorrhoea. This will not lead to ketone bodies synthesis. (WRONG).

Option B: When glycolysis is stimulated it will lead to increase concentration of pyruvate which gets converted into Acetyl CoA which enters TCA cycle. So no ketone formation occurs. (WRONG)

Option C: Acetyl CoA instead of going to TCA cycle enters the ketone bodies synthesis pathway and ketone bodies are formed. (CORRECT).

Option D:- Oxaloacetate should not be available for combining with Acetyl CoA which forces Acetyl CoA to do ketone synthesis. Hence this option is WRONG.

Option E: Proteins have no link with ketone bodies synthesis.