This document discusses polysaccharides and provides details about starch. It defines polysaccharides as polymers made of 10 or more monosaccharide molecules. Homopolysaccharides are made of identical monosaccharide units, such as starch, glycogen, and cellulose which are made of glucose. Starch consists of amylose, a linear polymer of glucose, and amylopectin, a branched polymer of glucose. The document describes tests to identify starch and other polysaccharides, noting that iodine forms complexes with starch that are blue for amylose and purple for amylopectin.

1. RITESH SRIVASTAVA
DEPARTMENT OF BIOCHEMISTRY
SHRIDEV SUMAN SUBHARTI MEDICAL COLLEGE
PREM NAGAR , DEHRADUN

2. These are made up of a large number of
monosaccharide molecules.
Polysaccharides made up of three to six molecules of
monosaccharides are termed as Oligosaccharides.
Ten or more than ten molecules of monosaccharides
are termed as Polysaccharides.

3. TYPES OF POLYSACCHARIDES
Polysaccharides are two types
Homopolysaccharides
Heteropolysaccharides

4. HOMOPOLYSACCHARIDES
Homopolysaccharides (Homoglycans) are the polymers
of identical Monosaccharide unit.
Common homopolysaccharides of biological
significance are STARCH, GLYCOGEN and
CELLULOSE (the homopolymers of glucose also
called GLUCOSANS) and Inulin ( the homopolymer of
FRUCTOSE also called FRUCTOSAN)

5. STARCH
 Starch is stored as a reservoir of food in cereals and
tubers of plants.
Starch consists of two polysaccharide, i.e. α-Amylose
and Amylopectin.
The α-Amylose is a linear polymer of glucose residues
linked by α-(1—4) glycosidic bond.
Amylopectin is a branched molecule with both α-(1—
4) straight chain and α-(1—6) branch points which
occurs after every 24 to 30 Glucose residues.

7. PRINCIPLE OF IODINE TEST
Absorption complex between starch and iodine is
formed. This complex dissociates on heating. The
complex is formed under the neutral or acidic
conditions. Under alkaline conditions, iodine reacts
with NaOH, so the blue color disappears. When alkali
is neutralized with acid, iodine is released and blue
color reappears.

8.  The color formed by the iodine test depends on the length of
the unbranched or linear ( α-1-4 linkage).
 Amylose (linear α -1-4 chain) gives deep blue color
amylopectin (branched chain compound) gives a purple color
while glycogen (highly branched structure) gives reddish
brown color.
 Dextrin that is formed by the partial degradation of starch gives
brownish red color as the chain length becomes smaller.
 On extensive degradation of starch, the corresponding dextrin
formed may not yield any color at all.

9. Aim - Study the reaction of Polysaccharide i.e.
Starch.
Physical characteristics-
1. Colour ------- Watery.
2. Appearance ------ Slightly Turbid.
3. Solubility ---- Soluble in hot Water .
4. Reaction ------ __________________.

10. TEST OBSERVATION INFERENCE
Molish Test
(General test for
carbohydarates)
3ml given sample + 2-3
drops Molisch’s reagent
and mix well + 2ml
conc. H2SO4 in
slanting Position. (do
not mix)
A reddish- Violet ring
Formed at the
Junction of two solution
Presence of
Carbohydrate
Iodine Test
(Test for
Polysaccheride)
3 ml given solution + 3-
4 drop iodine reagent
mix well and heat till it
boil.
Blue colour seen Presence of
polysaccharide (Starch)

11. Thank you