Ketone bodies (BC)

Topic: Metabolism Of Fatty Acids And Proteins

Ketone bodies, water-soluble molecules containing a ketone group, are produced from excess acetyl-CoA made during the oxidation of fatty acids from stored fats; they serve as a fuel source if glucose levels are too low in the body.

If excess acetyl-CoA is created from the oxidation of fatty acids, acetyl-CoA is diverted to create ketone bodies. Ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starvation or when patients suffer from uncontrolled diabetes and cannot utilize most of their circulating glucose. In both cases, fat stores are liberated to generate energy through the Krebs cycle and will generate ketone bodies when too much acetyl CoA accumulates.

Ketone bodies are produced through ketogenesis in the mitochondria of liver cells. Acetyl-CoA is converted into hydroxymethylglutaryl CoA (HMG CoA). HMG CoA is a precursor of cholesterol and is an intermediate that is subsequently converted into β-hydroxybutyrate, the primary ketone body found in the blood.


Practice Questions


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Key Points

• Ketone bodies serve as a fuel source if glucose levels are too low in the body.

• They are produced from excess acetyl-CoA that is created from the oxidation of fatty acids.

• The production of β-hydroxybutyrate, the primary ketone body found in the blood, comes from the excess acetyl-CoA that is diverted from the Krebs cycle to the ketogenesis pathway.


Key Terms

Ketone bodies: An alternative source of energy when glucose is limited, produced from acetyl-CoA originating from stored fats.

Ketone: A functional group with the structure RCR’.

Acetyl-CoA: A molecule that is involved in protein, carbohydrate and lipid metabolism by delivering an acetyl group to the citric acid cycle, which will be oxidized for energy production.

Oxidation: The loss of electrons from a molecule to oxygen; in the context of lipid metabolism, electrons are transferred from a fatty acid to oxygen, oxidizing the fatty acid.

Fatty acids: Lipids that contain a carboxylic acid functional group attached to a long-chain hydrocarbon tail.

Ketogenesis: The biochemical pathway through which ketone bodies are produced from the breakdown of fatty acids when glucose levels are too low in the body.

Hydroxymethylglutaryl CoA (HMG CoA): A molecule created in the first step of the production of ketone bodies from acetyl-CoA.

Cholesterol: A lipid that is found in the plasma membrane and are synthesized from acetyl-CoA.

β-hydroxybutyrate: The main ketone body found in the blood.



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