`beta-"pleated"`structure of protein is present in silk fibers , the prtein is

Options

A. Fibroin
B. Collagen
C. Rayon
D. Keratin

Answer

To determine the protein that exhibits a beta-pleated structure and is present in silk fibers, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Silk Fibers**: Silk fibers are produced by silk moths, and they are primarily composed of proteins.

2. **Identifying the Protein Structure**: The question specifies a "beta-pleated" structure, which is a type of secondary structure in proteins. This structure is characterized by beta strands connected laterally by hydrogen bonds, forming a sheet-like arrangement.

3. **Recognizing the Protein Type**: The protein that is known for having a beta-pleated sheet structure is fibroin. Fibroin is the main protein found in silk, and it is responsible for the strength and elasticity of silk fibers.

4. **Evaluating the Options**: The options provided are:
- a) Fibrin
- b) Collagen
- c) Rayon
- d) Keratin

Among these options:
- Fibrin is involved in blood clotting and does not primarily relate to silk.
- Collagen is a structural protein found in connective tissues but is not the main component of silk.
- Rayon is a synthetic fiber and not a protein.
- Keratin is a fibrous protein found in hair and nails, not in silk.

5. **Conclusion**: The correct answer is **Fibrin** (though it is important to note that the correct protein for silk is actually fibroin, which may have been a typographical error in the video).

### Final Answer:
The protein with a beta-pleated structure present in silk fibers is **Fibroin**.

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