Which of the amino acids has hydroxyl in its R-group
(a) Serine
(b) Alanine
(c) Arginine
(d) Proline

Options

A. Serine
B. Alanine
C. Arginine
D. Proline.

Answer

To determine which of the amino acids has a hydroxyl (-OH) group in its R-group, we will analyze each of the given options one by one.

### Step-by-Step Solution:

1. **Identify the R-groups of each amino acid:**
- **Serine (Ser)**: The R-group of serine is -CH2OH. This indicates the presence of a hydroxyl group (-OH).
- **Alanine (Ala)**: The R-group of alanine is -CH3. This does not contain a hydroxyl group.
- **Arginine (Arg)**: The R-group of arginine is more complex, consisting of -CH2-CH2-CH(NH2)2. There is no hydroxyl group present in this structure.
- **Proline (Pro)**: The R-group of proline is -CH2-CH2-CH2- which forms a ring structure. This does not include a hydroxyl group.

2. **Evaluate each option:**
- **(a) Serine**: Contains -OH in its R-group. **Correct option.**
- **(b) Alanine**: Does not contain -OH. **Incorrect option.**
- **(c) Arginine**: Does not contain -OH. **Incorrect option.**
- **(d) Proline**: Does not contain -OH. **Incorrect option.**

3. **Conclusion**: The amino acid that has a hydroxyl group in its R-group is **Serine**.

### Final Answer:
(a) Serine