What are ketones?

What are ketones?

• A. Breakdown products of fats and proteins that can provide energy as a temporary substitute for glucose.
• B. End products of glycolysis that increase ATP yield.
• C. Primary energy substrate during intense exercise.
• D. Enzymes that catalyze fat oxidation.

Answer: (A)

Ketones are energy-rich molecules produced mainly in the liver from fatty acids when carbohydrate availability is limited, such as during fasting or prolonged exercise. The main ketone bodies—acetoacetate, beta-hydroxybutyrate, and acetone—circulate in the blood and can be used by tissues like the brain, heart, and muscles for energy. They provide a temporary substitute for glucose, helping to spare glucose for tissues that rely on it. While some ketogenic amino acids can contribute to ketone formation, fats are the primary source. Ketones are not end products of glycolysis, not enzymes that catalyze fat oxidation, and they are not the main energy source during intense exercise, where glucose and glycolysis dominate.

Ketones are energy-rich molecules produced mainly in the liver from fatty acids when carbohydrate availability is limited, such as during fasting or prolonged exercise. The main ketone bodies—acetoacetate, beta-hydroxybutyrate, and acetone—circulate in the blood and can be used by tissues like the brain, heart, and muscles for energy. They provide a temporary substitute for glucose, helping to spare glucose for tissues that rely on it. While some ketogenic amino acids can contribute to ketone formation, fats are the primary source. Ketones are not end products of glycolysis, not enzymes that catalyze fat oxidation, and they are not the main energy source during intense exercise, where glucose and glycolysis dominate.