Which amino acid has no asymmetic carbon atom ?

Options

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

Answer

To determine which amino acid has no asymmetric carbon atom, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Amino Acids**:
- Amino acids are the building blocks of proteins and typically contain a central carbon atom (Cα) bonded to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a variable side chain (R group).

2. **Defining Asymmetric Carbon Atom**:
- An asymmetric carbon atom (also known as a chiral carbon) is a carbon atom that is attached to four different atoms or groups. This property allows for the existence of enantiomers (D and L forms) of amino acids.

3. **Identifying Amino Acids**:
- Most amino acids have at least one asymmetric carbon atom, which contributes to their chirality. However, we need to find the exception.

4. **Analyzing Glycine**:
- Glycine is the simplest amino acid. Its structure is NH2-CH2-COOH. The central carbon atom (Cα) in glycine is bonded to two hydrogen atoms (H) and two other groups (NH2 and COOH). Since it has two identical hydrogen atoms, it does not meet the criteria for being asymmetric.

5. **Conclusion**:
- Therefore, glycine is the only amino acid that does not have an asymmetric carbon atom.

### Final Answer:
The amino acid that has no asymmetric carbon atom is **glycine**.

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