What is produced by the liver and used as an energy source when glucose is not readily available?

• A. Ketone bodies
• B. Lactic acid
• C. Glycogen
• D. Insulin

Answer: (A)

Verified step by step guidance

1. Understand the role of the liver in metabolism: The liver is a key organ in regulating energy sources in the body, especially during fasting or low carbohydrate intake.
2. Identify the process of ketogenesis: When glucose is scarce, the liver converts fatty acids into ketone bodies through a process called ketogenesis. This occurs primarily in the mitochondria of liver cells.
3. Recognize the types of ketone bodies: The main ketone bodies produced are acetoacetate, beta-hydroxybutyrate, and acetone. These can be used by various tissues, including the brain, as an alternative energy source.
4. Differentiate between ketone bodies and other substances: Lactic acid is produced during anaerobic respiration, glycogen is a stored form of glucose, and insulin is a hormone regulating blood glucose levels. None of these are produced by the liver as an alternative energy source when glucose is low.
5. Conclude the liver's role in energy production: During periods of low glucose availability, the liver's production of ketone bodies is crucial for maintaining energy supply to vital organs.