Among the following the basic amino acid is

Options

A. Glycine
B. Argenine
C. Proline
D. Cysteine

Answer

To determine which among the given amino acids is a basic amino acid, we can follow these steps:

### Step 1: Understand the Definition of Basic Amino Acids
Basic amino acids are characterized by having a side chain that contains a basic group, which can accept protons (H+) at neutral pH. This typically means they have a higher pKa value.

### Step 2: Analyze Each Amino Acid
- **Glycine**: The structure of glycine is NH2-CH2-COOH. It has one amino group (NH2) and one carboxyl group (COOH). It does not have a basic side chain, so it is not a basic amino acid.

- **Arginine**: The structure of arginine is NH2-C(NH)-NH-CH2-CH2-COOH. It contains a guanidinium group (NH-C(NH)-NH2) in its side chain, which is basic and can accept protons. Thus, arginine is a basic amino acid.

- **Proline**: The structure of proline is NH-CH(CH2)-COOH. It has a secondary amine in its side chain but does not have a basic group that can accept protons. Therefore, proline is not a basic amino acid.

- **Cysteine**: The structure of cysteine is HOOC-CH(NH2)-SH. It has a thiol group (SH) in its side chain, which is not basic. Hence, cysteine is not a basic amino acid.

### Step 3: Conclusion
Among the amino acids listed (glycine, arginine, proline, and cysteine), the only basic amino acid is **arginine**.

### Final Answer
**Arginine** is the basic amino acid among the options provided.

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