Which of the following is not an essential amino acid?

Options

A. Glycine
B. Lysine
C. Phenyl alanine
D. Valine

Answer

To determine which of the following is not an essential amino acid, we need to understand the difference between essential and non-essential amino acids.

### Step-by-Step Solution:

1. **Define Essential Amino Acids**: Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet. There are nine essential amino acids in humans: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

2. **Define Non-Essential Amino Acids**: Non-essential amino acids are those that can be synthesized by the body. Examples include alanine, aspartic acid, serine, and glycine.

3. **List the Options**: If the question provides options, list them out. For this example, let’s assume the options are:
- A) Glycine
- B) Valine
- C) Lysine
- D) Threonine

4. **Identify Essential Amino Acids from Options**:
- Valine is an essential amino acid.
- Lysine is also an essential amino acid.
- Threonine is an essential amino acid.

5. **Identify Non-Essential Amino Acids from Options**:
- Glycine is a non-essential amino acid, meaning it can be synthesized by the body.

6. **Conclusion**: Since glycine is the only amino acid listed that is not essential, the answer to the question "Which of the following is not an essential amino acid?" is **Glycine**.

### Final Answer:
**Glycine** is not an essential amino acid.

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