Question

Silk fibres are made up of:
A. Vitamins
B. Carbohydrates
C. Protein
D. None of the above

Answer 1

Hint: As we know, silk is obtained naturally from cocoons of the larvae of the silkworm. Moreover, silk is a natural as well as a protein fibre too. So, it is a natural protein fibre.

Complete step by step answer: Silk fibres are one of the examples of the natural fibres. Silk fibres have a shiny appearance that we all have observed. The reason behind the shimmering appearance of silk is that it has the triangular prism-like structure of the silk fibre due to which the incoming light refracts at different angles producing different colours.
Silk is produced by several insects but the one produced by moth caterpillars is used for textile manufacturing.
Silk fibre is generally composed of fibroin and sericin. Sericin is known as the binding liquid which binds the solid fibre that is fibroin. They are made up of different amino acids from which glycine, alanine, serine is found to have the highest compositions.
The best silk is subtended from the cocoons of the larvae of the Mulberry silkworm Bombyx mori.
There are basically two steps that involve the production of the silk:
Taking care of the silkworm starting from the through the completion of the cocoon.
Production of the mulberry trees that actually provide the leaves that the worms feed.
The process of silk production is known as sericulture. The extraction of raw silk starts by cultivating the silkworms on Mulberry leaves. As the worms start pupating, they are made to be dissolved in warm water in order to get long fibres individually that can further be fed on the spinning reel. Silk fibres have a triangular cross section with rounded corners. The heavy chain of fibroid is made mostly of beta sheets. Silkworm fibres are naturally extruded from two silkworm glands as a pair of primary filaments, which are stuck together with series in proteins that act like a glue.
So, the correct answer is “Option C”.

Additional Information:
Silk is known to be one of the strongest natural fibres, but it loses up to $20\% $ of its strength when it is wet. It has good moisture regain. It is moderately elastic. If it is elongated even by a small amount it will remain stretched. It can be weakened if exposed to too much sunlight. It may also get attacked by insects, especially if left dirty.

Note: You should be amazed to know that in order to produce one kg of silk fibre, about $104{\text{ kg}}$ of Mulberry leaves are needed to feed approximately $3000$ silkworms. It takes about $5000$ silkworms to make a pure silk kimono. The major silk producers are China ($54\% $) and India ($14\% $) of total production.