Major amino acid released from muscle during starvation
## **Core Concept**
The question tests understanding of amino acid metabolism during starvation, specifically which amino acid is predominantly released from muscle tissue. During starvation, the body undergoes various metabolic changes to maintain energy homeostasis, including the breakdown of muscle protein.
## **Why the Correct Answer is Right**
The correct answer, **Alanine**, is a non-essential amino acid that plays a crucial role in glucose production through gluconeogenesis. During starvation, muscle breaks down its protein into amino acids. The amino groups are then transferred to pyruvate (a product of glycolysis) to form alanine via the action of the enzyme alanine transaminase. This process is known as the glucose-alanine cycle. Alanine is then transported to the liver, where it can be converted back into pyruvate and used for gluconeogenesis, providing a vital source of glucose for the brain and other tissues that prefer or exclusively use glucose for energy.
## **Why Each Wrong Option is Incorrect**
- **Option A: Leucine** - While leucine is a key amino acid involved in protein metabolism, it is primarily metabolized in the liver and is not the major amino acid released from muscle during starvation for gluconeogenesis.
- **Option B: Glutamate** - Glutamate is an important amino acid in amino group transfer reactions but is not specifically known for being the major amino acid released from muscle during starvation.
- **Option D: Aspartate** - Aspartate can participate in transamination reactions and is involved in gluconeogenesis but is not the primary amino acid released from muscles under starvation conditions.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is the **glucose-alanine cycle**, which is crucial during fasting or starvation. This cycle allows for the transport of amino groups from muscle to liver, facilitating gluconeogenesis and ensuring a steady supply of glucose to the brain and other tissues.
## **Correct Answer: C. Alanine**