Question

The gummy substance present in raw silk fibre is

• A. Serine
• B. Fibroin
• C. Keratin
• D. Sericin

Hint:

In silk, fibroin is the main structural protein, while sericin is the sticky protein that binds the fibroin strands together in raw silk.

Answer 1

The Correct Option is D

Silk is produced by the silkworm as a natural protein fibre. The raw silk fibre contains two proteins: fibroin and sericin. Fibroin is the structural protein that forms the silk fibre itself, while sericin is the gummy substance that holds the fibroin fibres together.

Step 1: Understand the composition of raw silk.
In raw silk, sericin is the sticky protein that serves as a protective coating around the fibroin threads. During the silk reeling process, sericin is removed to produce the finished silk fibre, which is smooth and shiny.

Step 2: Identify the correct substance.
- Serine is an amino acid, not a protein, so it is not the correct answer.
- Fibroin is the primary protein in silk, but it is not the gummy substance that holds the silk threads together. - Keratin is the protein found in hair, nails, and skin, not in silk.
- Sericin is the correct answer, as it is the gummy protein found in raw silk that is removed during processing.

Final Answer: \[ \boxed{\text{Sericin}}. \]