Question

Which among the following is NOT an essential amino acid?

• A. L-Phenylalanine
• B. L-Valine
• C. L-Lysine
• D. L-Arginine

Hint:

Remember: Arginine is {conditionally essential}—important during growth and in certain conditions, but not an essential amino acid in healthy adults.

Answer 1

The Correct Option is D

Step 1: Essential amino acids.
Essential amino acids cannot be synthesized by the human body and must be obtained through the diet. Examples include Valine, Lysine, Phenylalanine, Leucine, Isoleucine, Methionine, Threonine, Tryptophan, and Histidine. Step 2: Classification of given options.
- L-Phenylalanine: Essential.
- L-Valine: Essential (branched-chain amino acid).
- L-Lysine: Essential.
- L-Arginine: Semi-essential (conditionally essential, required mainly in children, can be synthesized in adults).
Therefore, the amino acid that is NOT strictly essential is L-Arginine.