What are the three ketone bodies and how do they differ from one another functionally (eg. in the way they are used)?

The three ketone bodies are Acetoacetate, Beta-hydroxybutyrate, and Acetone.

1. Acetoacetate: This is the first ketone body that is produced in the liver cells from fatty acids. It can be converted to either Beta-hydroxybutyrate or Acetone. Acetoacetate can be used by many tissues in the body as an energy source.

2. Beta-hydroxybutyrate (BHB): This is not technically a ketone due to its structure, but it is still classified as a ketone body and is the most abundant. It is formed from acetoacetate in the liver cells and can be used as an energy source in the brain when blood glucose is low.

3. Acetone: This is the least abundant and is formed from the spontaneous decarboxylation of acetoacetate. It cannot be used as an energy source and is mostly excreted in the breath and urine, although it can be used in the synthesis of glucose and fatty acids.

In terms of functional differences, acetoacetate and BHB can be used as energy sources by the body, especially during periods of fasting, low carbohydrate diets, or prolonged exercise. Acetone, on the other hand, is not used as an energy source but is instead excreted from the body.