What is carnitine?

What is carnitine?

• A. A trimethyl amino acid similar in structure to choline, it is required as a cofactor for transformation of free long-chain fatty acids into acylcarnitines and transport into the mitochondria.
• B. A carbohydrate used for energy storage in muscle.
• C. A peptide hormone regulating appetite.
• D. A fat-soluble vitamin involved in vision.

Answer: (A)

Carnitine acts as the shuttle that carries long-chain fatty acids into the mitochondria for beta-oxidation, enabling fat-derived energy production. It is a trimethylated amino acid with a structure similar to choline, which fits its role as a carrier rather than a storage molecule or hormone. In practical terms, fatty acyl-CoA cannot cross the mitochondrial membrane on its own. Carnitine forms an acylcarnitine via CPT I on the outer membrane, is transported into the matrix, and CPT II then transfers the acyl group back to CoA to form fatty acyl-CoA for oxidation. This recycling supports continuous fat burning, especially during prolonged activity or fasting. It is not a carbohydrate for energy storage, not a peptide hormone, and not a fat-soluble vitamin involved in vision, which is why the described statement aligns with the true nature of carnitine.

Carnitine acts as the shuttle that carries long-chain fatty acids into the mitochondria for beta-oxidation, enabling fat-derived energy production. It is a trimethylated amino acid with a structure similar to choline, which fits its role as a carrier rather than a storage molecule or hormone. In practical terms, fatty acyl-CoA cannot cross the mitochondrial membrane on its own. Carnitine forms an acylcarnitine via CPT I on the outer membrane, is transported into the matrix, and CPT II then transfers the acyl group back to CoA to form fatty acyl-CoA for oxidation. This recycling supports continuous fat burning, especially during prolonged activity or fasting. It is not a carbohydrate for energy storage, not a peptide hormone, and not a fat-soluble vitamin involved in vision, which is why the described statement aligns with the true nature of carnitine.