Question

What is a constituent of natural silk?
A) Phosphorus
B) Nitrogen
C) Potassium
D) Magnesium

Answer 1

Hint: Silk is a naturally occurring protein fiber produced from the larvae of the moth to build their cocoons. This fiber is used for the commercial production of silk fabric.

Complete answer:
Silk is a protein i.e. a polypeptide of the amino acids and the most important proteins of the silk fiber are fibroin and sericin. Fibroin is an insoluble protein. The primary structure of the proteins consists of the repeating sequence of amino acids (Gly-Ser-Gly-Ala-Gly-Ala)n.

Option A: The amino acids of the fibroin do not have a Phosphorus element. Therefore this is an incorrect option.

Option B: All the amino acids glycine, serine, and alanine have nitrogen as the common element present in their chemical formula. Therefore this is the correct option.

Option C: Potassium is not present as the constituent of fibroin and sericin proteins. Therefore this is an incorrect option.

Option D: Magnesium is not present in the chemical formula of amino acids present in fibroin and sericin proteins. Therefore this is an incorrect option.

Additional Information: The silk is produced by the larvae of the silkworm but the silk fiber is obtained from the cocoon of the larvae.

Thus, the correct answer is option (B) Nitrogen.

Note: Sericulture is the science of the farming of silkworms for the commercial production of silk fiber. The most commonly used silkworm for this process is Bombyx mori. Silk is a continuous thread of a usual length of about 500 to 900 meters in each cocoon.