Ketone bodies include which of the following compounds?

• A. Acetone
• B. Any three related compounds (acetone, acetoacetic acid, beta-hydroxybutyric acid)
• C. Acetoacetic Acid
• D. Beta-hydroxybutyric acid

Answer: (B)

Ketone bodies are the three water-soluble molecules produced by the liver to supply energy when glucose is scarce: acetone, acetoacetate (acetoacetic acid), and beta-hydroxybutyrate (beta-hydroxybutyric acid). Acetone comes from the spontaneous decarboxylation of acetoacetate and is mostly exhaled, not used for energy. The two others are used by tissues as energy sources after aerobic conversion to acetyl-CoA. Because this question asks which compounds are ketone bodies, the best choice lists all three, capturing the full set. The other options name only one component, making them incomplete.