Which of the following is a basic amino acid ?

Options

A. Lysine
B. proline
C. Alanine
D. Aspartic acid

Explanation

To determine which of the given amino acids is a basic amino acid, we need to analyze the structures of the amino acids provided: lysine, proline, alanine, and aspartic acid.

### Step-by-Step Solution:

1. **Identify the Amino Acids**: The amino acids provided in the question are lysine, proline, alanine, and aspartic acid.

2. **Draw the Structures**:
- **Lysine**: The structure of lysine includes an amino group (-NH2) in its side chain, which makes it basic.
- **Proline**: Proline has a cyclic structure and does not contain any additional amino or carboxylic acid groups in its side chain, making it neutral.
- **Alanine**: Alanine has a non-polar aliphatic side chain (methyl group -CH3), which is also neutral.
- **Aspartic Acid**: Aspartic acid has a carboxylic acid group (-COOH) in its side chain, which makes it acidic.

3. **Classify Each Amino Acid**:
- **Lysine**: Basic (due to the presence of the amino group in the side chain).
- **Proline**: Neutral (no basic or acidic groups).
- **Alanine**: Neutral (non-polar side chain).
- **Aspartic Acid**: Acidic (due to the carboxylic acid group).

4. **Conclusion**: Among the four amino acids, lysine is the only one that is classified as a basic amino acid.

### Final Answer:
The basic amino acid among the options provided is **Lysine**.

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