Question

Starch is composed of two polysaccharides namely:
 A) Amylopectin and glycogen.
 B) Amylose and glycogen.
 C) Amylose and Amylopectin.
 D) Amylose and Amylopectin and glycogen.

Answer 1

Hint: Starch is a colorless and odorless polysaccharide that is found in plants as stored carbohydrates. It is a polymer of glucose monomers that are linked with each other to form polysaccharide; it is a glucose polymer in which glucopyranose units are bonded by alpha-linkages.

Complete answer:
Starch has two types of units - Amylose and Amylopectin. Natural starch has a mixture of Amylose 15% - 20% and amylopectin 80% - 85%. Amylose and Amylopectin are polysaccharides of starch.
Amylose - Amylose consists of a linear chain of several hundred glucose molecules. It is a polysaccharide made of \[\alpha - D - glucose\] units, bonded to each other through \[\alpha - \left( {1,4} \right){\text{ }}glycosidic\] bonds. When iodine is added to starch, the colour changes to dark blue or black due to the presence of Amylose present in the starch. Amylose is soluble in water and can be hydrolyzed into glucose units by the enzymes \[\alpha - {\text{ }}amylase\] and \[\beta - amylase\].
Amylopectin - Amylopectin is a polymer of several \[D - glucose\] molecules. 80% of amylopectin is present in starch. Amylopectin molecules are linked by \[\alpha - 1,4 - glycosidic\] bonds and \[\alpha - 1,6 - glycosidic\] bonds. Amylopectin is a water-soluble polysaccharide and highly branched polymer of α-glucose units found in plants. When iodine is added to starch, it gives reddish-brown appearance due to the presence of amylopectin. It readily dissolves in hot water. On cooling, it forms a starch paste or starch gel.

Thus the correct option is (C).

Note: Starches are insoluble in water. They can be digested by hydrolysis, catalyzed by enzymes called amylases, which can break the $\alpha$-linkages (glycosidic bonds).