Question

Which one of the following contains protein units in its molecules?
A.Cotton
B.Wool
C.Nylon
D.Rayon

Answer 1

Hint:To answer this question, you must recall the structure and properties of the given molecule. Fibres can be either man made or synthetic. A natural fibre is more likely to be composed of protein molecule units.

Complete answer:
Wool is a fibre that contains protein units in its molecules. It is a type of a natural protein fibre which is formed by the condensation of amino acids with a small percentage of lipids forming repeated polyamide structural units.
Wool has been used for thousands of years by people for both decorative as well as functional uses. It is obtained from the outer covering of hair of sheep and other animals living in cold places. The wool fibres are poor conductors of heat and thus trap the air below them. As a result, they do not let warmth escape from the body and thus protect the body from cold. Wool fibres are also extremely flexible, highly durable and are water resistant.

Thus, the correct answer is B.

Note:
Natural fibers are fibers obtained from natural sources like plants and animals. Some common examples of natural fibres are cotton, silk, wool, etc.
Synthetic fibers are the fibers which are prepared by human beings in laboratories. They are polymers formed by repeating units of various monomers. Various synthetic fibers used commonly are nylon, acrylics and polyesters. Synthetic fibers are preferred over natural fibers as they are durable and elastic. Synthetic fibers are strong, soft and cheaper as compared to natural fibers.