Question

Which among the following is the monomer of starch?
(A) Glucose
(B) Sucrose
(C) Fructose
(D) Lactose

Answer 1

Hint: A monomer is defined as the smallest or the basic unit of the polymer. Monomers are the repeating structural units that are derived from some simple and reactive molecules. Monomers are linked to each other by a covalent bond. We will find the basic unit which on repetition forms starch.

Complete step by step answer
As we are aware of the isomers we can easily predict the monomer of starch. Now, we will discuss some points about starch. Starch is a polymer that is formed by the repeated unit of glucose. Therefore, glucose is the basic unit of the polymer starch. Hence, glucose is considered as the monomer of starch. Now we will discuss the structure of the monomer glucose and its polymer starch.
As we know that polymers are defined as very large molecules that have very high molecular masses. Starch is also a polymer. The other name of starch is amylum. Some of the important sources of starch are wheat, rice, maize, potatoes, legumes, and other vegetables. The polymer starch is stored in the liver in the form of glycogen.
Now the structure of the polymer. Starch is a homopolysaccharide and on hydrolysis give many molecules of $ \alpha - D $ -glucose. Starch has two structural constituents. Amylose and Amylopectin are the two components of starch. Amylose is the water-soluble constituent and amylopectin is the water-insoluble constituent.
Therefore, the correct option is (A).

Note:
Cellulose is also made from the monomer glucose. But the difference is that in starch all the glucose repeated units are oriented in the same direction and in cellulose each successive glucose unit is rotated $ {180^0} $ around the axis of the polymer.