Which of the following amino acid is basic in nature ?

Options

A. Valine
B. Tyrosine
C. Arginine
D. Leucine

Answer

To determine which amino acid is basic in nature from the given options (valine, threonine, arginine, and leucine), we can analyze the structure and properties of each amino acid.

### Step-by-Step Solution:

1. **Understanding Amino Acids**:
- Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid contains an amino group (-NH2), a carboxyl group (-COOH), and a variable side chain (R group).

2. **Identifying the R Groups**:
- Each amino acid has a unique R group which determines its properties. We need to analyze the R groups of the given amino acids:
- **Valine (Val)**: R group is isopropyl (CH(CH3)2).
- **Threonine (Thr)**: R group is hydroxyl (CH(OH)CH3).
- **Arginine (Arg)**: R group is guanidinium (NH2-C(=NH)-NH).
- **Leucine (Leu)**: R group is isobutyl (CH2-CH(CH3)2).

3. **Analyzing Basicity**:
- Basic amino acids contain side chains that can accept protons (H+). This is often due to the presence of additional amino groups or other basic functional groups.
- **Valine**: Neutral, does not have a basic group.
- **Threonine**: Neutral, does not have a basic group.
- **Arginine**: Contains a guanidinium group which is positively charged at physiological pH, making it basic.
- **Leucine**: Neutral, does not have a basic group.

4. **Conclusion**:
- Among the given options, **arginine** is the only amino acid that is basic in nature due to its guanidinium group.

### Final Answer:
The amino acid that is basic in nature is **arginine**.

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