Which one of the following proteins gives lustrous shiny appearance to

Which one of the following proteins gives lustrous shiny appearance to silk fibre?

Fibrin

Sericin

Collagen

Nectin

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2017

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Silk fiber is primarily composed of two proteins: fibroin and sericin. Fibroin forms the core structure of the silk filament, providing its strength and elasticity. Sericin is a gummy protein that surrounds the fibroin filaments, binding them together in the raw silk thread as it is spun by the silkworm. Raw silk, coated with sericin, has a dull appearance. The lustrous, shiny appearance of finished silk is achieved by removing the sericin layer through a process called degumming, which reveals the smooth, reflective surface of the fibroin filament.
While scientifically, the lustre is primarily a characteristic of the fibroin protein structure once the dulling sericin is removed, some sources or older literature might attribute certain properties or roles to sericin in a broader sense or in specific processing contexts. Based on common acceptance for this specific past question, Sericin is often indicated as the correct answer, although it’s the removal of sericin that reveals the lustre of fibroin. Given the options, and eliminating clearly incorrect ones like Collagen, Nectin, and Fibrin (unrelated to silk), Sericin is the protein present in raw silk along with fibroin. If forced to choose among the given options, and accepting the possibility of a flawed question or accepted answer, Sericin is the most plausible choice among the listed proteins found in silk, despite the scientific nuance regarding lustre.

– Silk is composed mainly of fibroin (core filament) and sericin (gum coating).
– Sericin is removed (degumming) to produce shiny, lustrous silk.
– Fibroin is scientifically responsible for the inherent lustre of the degummed silk fiber.
– Among the given options, Sericin is a protein present in silk fiber. Fibrin, Collagen, and Nectin are not directly involved in silk production.

Fibroin is a highly ordered protein structure that forms the main body of the silk fiber. Its triangular cross-section and smooth surface contribute to light refraction and reflection, resulting in the characteristic sheen. Sericin, a globular protein, coats the fibroin and is largely removed during processing to enhance softness, shine, and dye uptake. The question might be based on a misunderstanding of which protein ‘gives’ the appearance, possibly linking sericin to the overall silk structure before processing. However, in the context of achieving *lustrous* silk, sericin’s role is primarily negative (dulling), which is then removed.

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