Question

Which of the following is an essential amino acid?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Essential amino acids such as valine, leucine, and lysine play a crucial role in protein synthesis and metabolism. They are found in foods like meat, dairy, and legumes.

Answer 1

The Correct Option is C

Step 1: Understanding Essential Amino Acids. 
- Amino acids are organic compounds containing amino (-NH\(_2)\) and carboxyl (-COOH) functional groups.
- Essential amino acids cannot be synthesized by the human body and must be obtained from dietary sources. 

Step 2: Identifying the Essential Amino Acid. 
- Valine (\(H_2N-CH(CH_3)_2-COOH\)) is an essential amino acid.
- It is necessary for muscle growth, tissue repair, and energy production.
- The other given options include:
- Alanine (\(H_2N-CH(CH_3)-COOH\)) – a non-essential amino acid.
- Serine (\(H_2N-CH_2OH-COOH\)) – a non-essential amino acid.
- Cysteine (\(H_2N-CH_2SH-COOH\)) – a non-essential amino acid. 

Step 3: Conclusion. Since valine is an essential amino acid that must be obtained through diet, option (3) is correct.