Polysaccharide

Polysaccharide introduction, example, structure, starch, cellulose, chitin those structure and important functions and their presence in plants and animals, polysaccharide types based on functions and their composition , functions of polysaccharides , important images for relevant polysaccharides types, polysaccharide role in plants and animal cells. Starch - structure and functions, cellulose structure and functions, chitin - structure and functions

1. Polysaccharides
Presented by:
Jasmine Juliet
Biochemistry, ACRI, Madurai.

2. Polysaccharides -Introduction
Polysaccharides are complex biomacromolecules.
Polysaccharides orpolycarbohydrates, are the most
abundantcarbohydratefound in food.
They are long chainpolymericcarbohydrates.

3. Polysaccharides -Structure
Polysaccharides are composed ofmonosaccharideunits bound together
byglycosidic linkages.
They are either linear or branched in structure.
Polysaccharides may also be classified based on their function:
(i) Structural polysaccharidesare usually present in the cell walls
and give shapeand rigidity to the cells.Eg. Cellulose, hemicelluloses
(ii) Storage polysaccharidesact as reserve food material.Eg. Starch,
glycogen

4. Polysaccharides -Structure
Polysaccharides may be sub-classified into two types based on
the compositionof monosaccharideunits present.
Homopolysaccharidesare made up of a single type of
monosaccharide.Eg:starch, glycogen, cellulose, inulin.
Heteropolysaccharidesare made up of more than one type
ofmonosaccharides.Eg: Hemicelluloses,arabinogalactan

5. Polysaccharide -Starch
Starch is a storage polysaccharide in plant cells.
It is a homopolymer of α-D-glucose units.
Starch has two main constituents.
(i) Amylose (15-20%) Linear polysaccharides
(ii) Amylopectin(80-85%) branched polysaccharides

7. Polysaccharide -Cellulose
Celluloseis an example of astructuralpolysaccharide.
It is used in thecell wallsof plants and other organisms, and
is said to be the most abundantorganic molecule.
Cellulose is formed whenβ-glucosemolecules are joined to
form a polymer.
It is a straight chain polymer.
Furthermore, due to the hydrogen bonds between molecules it
can form very rigid fibers.

10. Polysaccharide -Chitin
Chitinis a structural polysaccharide found in the
exoskeleton of insects and crustaceans and in the cell
walls of fungi.
It consists of N-acetyl-D-glucosamine units joined by
β-1,4 glycosidic linkages.
Like cellulose it consists of parellel chains of molecules
held together by hydrogen bonds.

11. Chitin

12. Polysaccharide -Functions
The three main functions of polysaccharides are:
(i) providing structural support,
(ii) storing energy, and
(iii) sending cellular communication signals.
The carbohydrate structure largely determines its
function.

13. Review questions
A1. An example of heteropolysaccharideis
a)Amyloseb)Hemicellulosec)Cellulose d) Amylopectin
A2. The repeating unit in chitin
a)Glucose b)Glucosamine c)Galactosed)N-acetyl glucosamine
A3. Glucose residues in amyloseare linked by
a)α1-4 b)β1-4c)α1-6 d)β1-6
A4.Which of the following is an example of homopolysaccharide
a)Starch b)Glycogenc)Cellulose d) All of these

14. Review questions
B1.Define polysaccharide?
Ans: Polysaccharides are composed ofmonosaccharideunits
bound together byglycosidiclinkages.Eg:Starch, cellulose.
C1. Describe the structure of starch?
Ans: Starch is a homopolymerof α-D-glucose units.Starchhas
two main constituents (i) Amylose(15-20%) Linear
polysaccharides, (ii) Amylopectin(80-85%) branched
polysaccharides

15. Review questions
D1. Explain the classification of polysaccharides with
examples?