**Question:** Carnitine is made-up of:

A. L-methionine
B. L-lysine and L-glycine
C. L-lysine and L-methionine
D. L-methionine and L-phenylalanine

**Core Concept:** Carnitine is an essential nutrient involved in fatty acid oxidation in mitochondria. It plays a crucial role in maintaining cellular energy production by facilitating the transport of long chain fatty acids into mitochondria for beta-oxidation. The correct structure of carnitine consists of two L-amino acids joined by an amide bond.

**Why the Correct Answer is Right:** Carnitine is made up of two L-amino acids, which are L-lysine and L-methionine. The correct answer (C) highlights that L-lysine and L-methionine are the two L-amino acids forming carnitine. These amino acids are combined through an amide bond to form the complete molecule.

**Why Each Wrong Option is Incorrect:**

A. L-methionine and L-phenylalanine: This option incorrectly identifies two amino acids that are not part of carnitine's structure. L-phenylalanine is not involved in carnitine synthesis.

B. L-lysine and L-glycine: L-glycine is not part of carnitine's structure. The correct amino acids are L-lysine and L-methionine.

C. L-lysine and L-methionine: This option correctly identifies L-lysine and L-methionine as the building blocks of carnitine, further emphasizing their roles in carnitine synthesis.

D. L-methionine and L-phenylalanine: As mentioned before, L-phenylalanine is not part of carnitine's structure, making this option incorrect.

**Clinical Pearl:** Understanding the structure and function of carnitine is essential for medical professionals as it plays a vital role in cellular energy production and maintaining cardiovascular health. A deficiency in carnitine can lead to heart and skeletal muscle problems. Supplementing carnitine can help improve cardiovascular health and increase endurance in athletes.