Topics:
Animal Nutrition, Animal Refresher
Identification of Ketogenic Amino Acids
Which of the following is a ketogenic amino acid?
- Leucine — Correct Answer
- Alanine
- Glutamic acid
- Isoleucine
Explanation:
Correct Answer: Leucine
Leucine is the classic example of a purely ketogenic amino acid — it is degraded exclusively into Acetyl CoA and Acetoacetate, which are ketone body precursors. It cannot contribute to gluconeogenesis.
Amino Acid Classification by Metabolic Fate
| Category | Examples | Products |
|---|---|---|
| Purely Ketogenic | Leucine (only pure one) | Acetyl CoA, Acetoacetate |
| Glucogenic & Ketogenic | Isoleucine, Lysine, Phenylalanine, Tyrosine, Tryptophan, Threonine | Both gluconeogenic and ketogenic products |
| Purely Glucogenic | All other amino acids (Alanine, Glutamate, etc.) | Pyruvate, OAA, α-ketoglutarate |
Clinical Relevance
- In starvation or uncontrolled diabetes: protein catabolism → excess Leucine → ketone body accumulation → ketosis.
- BCAA (Branch Chain Amino Acids): Leucine, Isoleucine, Valine — metabolized in muscle, not liver.
- Leucine also activates mTOR pathway → stimulates muscle protein synthesis.
Why Other Options Are Wrong
- Alanine → purely glucogenic → pyruvate → gluconeogenesis.
- Glutamic acid → purely glucogenic → α-ketoglutarate → TCA cycle.
- Isoleucine → both glucogenic AND ketogenic; not purely ketogenic like Leucine.
📚 About this Topic — Animal Nutrition
This multiple choice question is from Animal Nutrition, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Nutrition to strengthen your preparation.
