Which of the following amino acid is not optically active and has achiral carbon ?

Options

A. Alanine
B. Serine
C. Glycine
D. Lysine

Answer

To determine which amino acid is not optically active and has an achiral carbon, we need to analyze the chirality of the given amino acids: alanine, serine, glycine, and lysine.

### Step-by-Step Solution:

1. **Understand Chirality**:
- Chirality refers to a molecule that has a non-superimposable mirror image. A chiral carbon atom is one that has four different substituents attached to it.

2. **Analyze Each Amino Acid**:
- **Alanine**:
- Structure: NH2-CH(CH3)-COOH
- The carbon atom (C) attached to the NH2, COOH, H, and CH3 groups has four different substituents. Therefore, alanine is chiral and optically active.

- **Serine**:
- Structure: NH2-CH(CH2OH)-COOH
- The carbon atom (C) attached to the NH2, COOH, H, and CH2OH groups also has four different substituents. Thus, serine is chiral and optically active.

- **Glycine**:
- Structure: NH2-CH2-COOH
- The carbon atom (C) attached to the NH2, COOH, and two H atoms (H and H) does not have four different substituents. Therefore, glycine is achiral and not optically active.

- **Lysine**:
- Structure: NH2-CH(CH2CH2NH2)-COOH
- The carbon atom (C) attached to the NH2, COOH, H, and CH2CH2NH2 groups has four different substituents. Hence, lysine is chiral and optically active.

3. **Conclusion**:
- Among the options, glycine is the only amino acid that is not optically active and has an achiral carbon.

### Final Answer:
Glycine is the amino acid that is not optically active and has an achiral carbon.

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