Oligosaccharides are carbohydrates made of 2-6 monosaccharides joined by glycosidic linkages. The most common are disaccharides made of two monosaccharides. Examples of disaccharides include maltose from two glucose units, lactose from glucose and galactose, and sucrose from glucose and fructose. Polysaccharides are carbohydrates made of many monosaccharides joined by glycosidic linkages and can be homopolysaccharides made of one type of monosaccharide like starch and cellulose, or heteropolysaccharides with different types of monosaccharides like hyaluronic acid. Starch is a plant polysaccharide made of amylose and amylopectin

1. MSCDFSM BIOCHEMISTRY
CARBOHYDRATE III

2. OLIGOSACCHARIDES : when 2 to 6 monosaccharides join together by a linkage
Known as glycosidic linkage , it results in glyosidic linkage .
On the basis of no of monosaccharides oligosaccharides are divided into
disaccharides ,trisaccharides .most common compounds are disaccharides .
DIASACHHARIDES : These are compounds made of 2 monosaccharides joined
by glyosidic linkage
E.g. .Maltose - made of 2 glucose
Lactose – made of glucose and galactose
Sucrose – made of glucose and fructose
GLYCOSIDIC LINKAGE This bond is formed through reaction between –OH group
on anomeric carbon atom of one unit and –OH group of other unit .
In sucrose ,the second –OH group is contributed by anomeric carbon atom but in
maltose and lactose it is contributed by carbon atom 4 .thus the confugration
of each disaccharide is different according to the unit contributing the
anomeric carbon atom α (1 2)glycosidic linkage in sucrose. α (1
4)glycosidic linkage in maltose β (1 4 )in lactose
TRISACCHARIDES These are the compounds that made up of 3
monosachharides
Eg .raffinose made up of galactose , glucose and fructose .

3. POLYSACHHARIDES :
When many monosachharides join together by glycosidic linkage is called
polysaccharides.
Polysaccharides are of two types :
1. HOMOPOLYSACHHARIDES
2. HETEROPOLYSACHHARIDES
HOMOPOLYSACHHARIDES : These are also called homoglycans that posses only one
type of monosachharides .eg. Starch and cellulose
HETEROPOLYSACCHARIDES : These are also called heteroglycans that posses that
posses different form of monosachharides .eg. Hyaluronic acid and heparin .
STARCH : It is a plant polysachharide synthesized by plant through photosynthesis ,
stored in grain , egume ,roots ,tuber .
MOLECULAR FORMULA – (C6 H10 O5 )n
Starch consist of 2 forms 1. amylose (15- 35%) and 2. amylopectin (65-85%)
Amylose is straight chain compound formed by 250-300 glucose residues joined
together by (1,4)glycosidic linkage
Amylopectin is highly branched polymer and branching occurs at intervals of 24-30
glucose residues.glucose units of main chain are joined by α (1,4)glycosidic linkage and
glucose units at the branch are joined by α (1,6)glycosidic inkage to main chain

4.  Starch is not soluble in water and form colloids in aqueous medium called as
miscelles. Iodine reacts with both amylose and amylopectin but amylose gives
blue colour and amylopectin gives violet colour .when starch reacts with iodine
it gives blue colour as the violet colour get masked by blue colour so we
observe bue colour of solution .this colour complex dissociate on heating and
reforms again on cooling .
 Starch is non reducing substance because all carbonyl groups are involved in
making gycosidic bond formation .
When boiled with HCL or acted by amylase ,it gives free glucose.
CELLULOSE
 It is present in pant cellwall.it is not present in animal body .it is homopolymer
of glucose .the difference lies in linkage .in starch linkage is α (1 4)but in
cellulose the linkage is β(1 4).so , cellulose is madeup of β glucose molecules
linked by β (1 4)glycosidic linkage .
 It is not acted by amylase
 Strong HCL hydrolyses cellulose to glucose
GLYCOGEN
It is polysachharidefound in muscle,liver of animals,and human.it is branched
polymer with 8-10 glucose units in each branch.its straight chain formed by α(1,4)
linkage and β(1,6)glycosidic linkage .each glycogen contain 5000- 10000 glucose
units
It is soluble in water and gives red colour with iodine .

5. DEXTRINS:
These are the polymers of D-glucose held by α (1,4) gLycosidic linkage
When starch hydrolyse partially by salivary amylase .,dextrins are formed .
In water, dextrin form sticky solution and are frequently used as adhesive eg
.postage stamps .
They hydrolyse yield maltose and finally glucose.
INULIN :
it is plant polysachharide made up of fructose ,soluble in warm water and no
colour with iodine .
These are polymers of fructose units that typically have terminal glucose .
Inulin are sweet in taste and are present in vegetables and fruits like onion ,
garlic , banana etc

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