Page 15 - Lesson Notes - Biomolecules 1

Some of them are as fallows
a. Cellulose
It is a polymeric polysaccharide which consists of only one type of monosaccharide
monomer, i.e., glucose. It is known to be a rigid and insoluble polysaccharide found
in cell wall of most algae, certain protists, fungi and some higher plant.
Paper made from pulp of plant and cotton fibre are also made up of cellulose. As
cellulose is not composed of complex helices so, it cannot hold iodine (I 2) and
cannot give colour with iodine.
b. Starch
It is a storage polysaccharide because it helps in storing energy in plant tissues.
Chemically, the starch is formed of two glucose monomers, r.e.,α-amylose and
amylopectin.
Starch forms helical secondary structures. Thus, it can hold iodine (I 2) molecules in
the helical portion. Therefore, gives blue colour with iodine solution.
c. Glycogen

It is also storage polysacchiaride found in animals only (in liver cells and muscles). It
is also known as animal starch. It gives red colour on reaction with iodine.
It is a polymer of fructose. It is a naturally occurring polysaccharide produced by
many types of plants. It is used by some plants in storing energy.
Plants that synthesis and store inulin are unable to store other forms of
carbohydrates like starch, etc.
Agar, xylan, araban, etc, are some other types of homopolysaccharides found.
ii. Heteropolysaccharides
These are complex carbohydrates formed by the polymerisation of two or more than