Which of the following is an examples of fibrous protein?

Options

A. Insulin
B. Haemoglobin
C. Fibroin
D. Glycogen

Explanation

To determine which of the following is an example of a fibrous protein, we need to understand the characteristics of fibrous proteins and analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Fibrous Proteins**:
- Fibrous proteins are characterized by their thread-like structure.
- They have strong intramolecular bonds, which include hydrogen bonding and dipole-dipole interactions.
- Due to these strong bonds, fibrous proteins exhibit high tensile strength but low elasticity.
- They can be woven into fabrics, which is a key feature of fibrous proteins.

2. **Analyzing the Options**:
- **Option 1: Insulin**:
- Insulin is a simple polypeptide consisting of amino acids and has a specific structure with two chains (A-chain and B-chain) connected by disulfide bonds.
- Insulin is classified as a globular protein, not fibrous.

- **Option 2: Hemoglobin**:
- Hemoglobin has a quaternary structure with four polypeptide chains (two alpha and two beta chains).
- It is also a globular protein and does not have the thread-like structure characteristic of fibrous proteins.

- **Option 3: Fibroin**:
- Fibroin is a silk protein and is known for its fibrous structure.
- It is indeed a fibrous protein, making it suitable for fabric production.

- **Option 4: Glycogen**:
- Glycogen is a polymer of glucose and is classified as a carbohydrate, not a protein.
- Therefore, it cannot be considered a fibrous protein.

3. **Conclusion**:
- After analyzing all the options, the only example of a fibrous protein is **Fibroin** (Option 3).

### Final Answer:
The correct answer is **Option 3: Fibroin**.