Imino acid among these compounds is

Options

A. Serine
B. Proline
C. Tyrosine
D. Lysine

Answer

To determine which of the given compounds is an imino acid, we need to analyze the structures of each compound: serine, proline, tyrosine, and lysine.

### Step 1: Understand the Definition of Imino Acid
An imino acid is characterized by the presence of a secondary amine group (NH group) in its structure. This is different from standard amino acids, which contain a primary amine group (NH2).

### Step 2: Analyze Each Compound
1. **Serine**:
- Structure: HO-CH(CH2OH)-COOH
- Contains: An NH2 group (primary amine).

2. **Tyrosine**:
- Structure: HO-C6H4-CH(NH2)-COOH
- Contains: An NH2 group (primary amine).

3. **Lysine**:
- Structure: NH2-(CH2)4-COOH
- Contains: An NH2 group (primary amine).

4. **Proline**:
- Structure: A five-membered ring with NH and COOH.
- Contains: An NH group that is part of a ring structure, making it a secondary amine.

### Step 3: Identify the Imino Acid
Among the compounds analyzed, proline is the only one that contains a secondary amine group due to its cyclic structure. Therefore, proline is classified as an imino acid.

### Final Answer
**Proline is the imino acid among the given compounds.**

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