Which of the following is a non-essential amino acid?

Proline

The correct answer is option 1. Proline.

Essential Amino Acids: These are amino acids that cannot be synthesized by the human body and must be obtained through the diet. They are crucial for various bodily functions and processes.

Non-Essential Amino Acids: These amino acids can be synthesized by the body from other compounds and do not necessarily need to be obtained from dietary sources.

Amino Acids in the Options

1. Proline:

Classification: Non-essential.

Proline can be synthesized in the body from other amino acids and is not required to be included in the diet. It is produced through the conversion of glutamate.

2. Leucine:

Classification: Essential

Leucine is required for protein synthesis and various metabolic processes. Since the body cannot produce it, it must be obtained through dietary sources.

3. Threonine:

Classification: Essential

Threonine is involved in various functions including protein synthesis and the formation of important molecules. It must be acquired through diet.

4. Lysine:

Classification: Essential

Lysine is vital for protein synthesis and various other biological functions. It cannot be synthesized by the body and must be obtained from food sources.

Summary

Proline is classified as a non-essential amino acid because the body can produce it from other amino acids and does not need to be supplied directly through diet.

Leucine, Threonine, and Lysine are essential amino acids because they must be obtained from dietary sources as the body cannot synthesize them.