Which amino acid does not contain chiral centre ?

Options

A. Valine
B. Leucine
C. Glycine
D. Iso-leucine

Explanation

To determine which amino acid does not contain a chiral center, we need to understand what a chiral center is. A chiral center, often a carbon atom, is defined as a carbon atom that is bonded to four different groups. If a carbon atom does not meet this criterion, it is not considered chiral.

### Step-by-Step Solution:

1. **Identify the Amino Acids**: The amino acids given in the question are:
- Glycine
- Alanine
- Glutamine
- Isoleucine

2. **Understand Chiral Centers**: Recall that a chiral center is a carbon atom bonded to four different substituents. If a carbon atom has two or more identical substituents, it is not chiral.

3. **Analyze Glycine**:
- Glycine has the structure: NH2-CH2-COOH.
- The central carbon (C) in glycine is bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom (H)
- Another hydrogen atom (H)
- Since it has two hydrogen atoms, it does not have four different groups attached. Therefore, glycine does not have a chiral center.

4. **Analyze Alanine**:
- Alanine has the structure: NH2-CH(CH3)-COOH.
- The central carbon in alanine is bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom (H)
- A methyl group (CH3)
- All four substituents are different, making alanine chiral.

5. **Analyze Glutamine**:
- Glutamine has the structure: NH2-CH(CH2NH2)-COOH.
- The central carbon in glutamine is bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom (H)
- A side chain (CH2NH2)
- All four substituents are different, making glutamine chiral.

6. **Analyze Isoleucine**:
- Isoleucine has the structure: NH2-CH(CH(CH3)2)-COOH.
- The central carbon in isoleucine is bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom (H)
- A side chain (CH(CH3)2)
- All four substituents are different, making isoleucine chiral.

7. **Conclusion**: After analyzing all the given amino acids, we find that glycine is the only amino acid that does not contain a chiral center.

### Final Answer:
The amino acid that does not contain a chiral center is **Glycine**.