Essential amino acid among the following is

Options

A. Glycine
B. Tryptophan
C. Alanine
D. Proline

Answer

To determine which of the following amino acids is essential, we need to understand the difference between essential and non-essential amino acids.

### Step-by-Step Solution:

1. **Definition of Essential Amino Acids**:
- Essential amino acids are those that cannot be synthesized by the body and must be obtained through the diet. There are nine essential amino acids in total.

2. **List of Amino Acids Given**:
- The amino acids provided in the question are glycine, tryptophan, alanine, and proline.

3. **Classification of Each Amino Acid**:
- **Glycine**: This is a non-essential amino acid, meaning the body can produce it.
- **Tryptophan**: This is an essential amino acid; the body cannot synthesize it and must be obtained from food.
- **Alanine**: This is also a non-essential amino acid, as it can be synthesized by the body.
- **Proline**: This is another non-essential amino acid, which the body can produce.

4. **Conclusion**:
- Among the amino acids listed, tryptophan is the only essential amino acid. Therefore, the answer to the question is tryptophan.

### Final Answer:
The essential amino acid among the following is **tryptophan**.

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