Relaxin is chemically

Options

A. steroid
B. protein
C. carbohydrate
D. both (1) and (3)

Answer

**Step-by-Step Solution:**

1. **Understanding Relaxin**: Relaxin is a hormone that is involved in various physiological processes, particularly during pregnancy. It plays a role in the relaxation of pelvic ligaments and the cervix.

2. **Chemical Classification**: The question asks about the chemical nature of relaxin. The options provided are steroid, protein, carbohydrate, or a combination of steroid and carbohydrate.

3. **Comparing with Insulin**: Relaxin is structurally similar to insulin, which is a well-known protein hormone. Insulin consists of two peptide chains (A and B chains) connected by disulfide bonds.

4. **Structure of Relaxin**: Relaxin is also a heterodimer, meaning it consists of two different peptide chains. In the case of relaxin, one chain has 24 amino acids and the other has 29 amino acids. These chains are linked by disulfide bonds, similar to insulin.

5. **Peptide Chains and Proteins**: Peptide chains are formed by amino acids. A protein is essentially made up of one or more polypeptide chains. Since relaxin consists of peptide chains, it is classified as a protein.

6. **Exclusion of Other Options**:
- **Steroid**: Relaxin does not belong to the steroid category, which is typically derived from cholesterol and has a different structure.
- **Carbohydrate**: Relaxin does not fit into the carbohydrate category, which consists of sugars and their derivatives.
- **Combination of Steroid and Carbohydrate**: Since relaxin is a protein, this option is also incorrect.

7. **Conclusion**: Based on the above analysis, relaxin is chemically classified as a protein.

**Final Answer**: Relaxin is chemically a protein.

---