Polysaccharides:
Definition
Polysaccharides ( or simply glycans)
Consist of repeating unit of monsaccharides or their derivatives held to gether by glycosidic bonds .
They perform two functions
1) structural or storage of energy
Types of polysaccharides
1) Homopolysaccharides
2)Heteropolysaccharides
1) HOMOPOLYSACCHARIDES
On hydrolysis yield only a single type of monosaccahrides they are named based on the nature of the monosaccharides thus glucans are polymers of glucose while fructosans are polymer of fructose
Examples
1) Starch
2Dextrins
Cellulose
4Glycogen
Chitin
Heteropolysaccharides
ON hydrolysis yield a mixture of few monosaccharides and their derivatives
Examples
1)Hyalunuric acid
2) chondroitin sulphate
3 Heparin
Homopolysaccharids (starch)
Starch;
Starch is the carbohydrate reserve of plants which is the most important dietry source of higher animals including man higher content of starch is found in cereals ,roots, tubers, vegetables starch is the homoploysaccharides composed of D glucose held by glycosidic linkages starch consiats of teo polysaccharides amylose and amylopectin ; amylose 15 to 20% and amylopectin is 80 to 85%
1 (AMYLOSE)
2( AMYLOPECTIN)
Amylose is a long unbranched chain with 200-1000 D glucose units held by glycosidic linkage and it is water soluble
Amylopectin
On the other hand is a branched chain with a 1-4 and 1-6 glycosidic linkage amylopectin molecule cintaining a few thosands glucose units look like a branched tree 20 -30 glucose units per branch
2DEXTRINS
Dextrins are the hydrolytic products of starch by the enzyme amylase
GLYCOGEN
Glycogen is the carbohydrate reserve in animals hence known as animal starch it is present in high concentration in liver muscle and brain etc
Glucose is the repeating unit in glycogen 15000 units of glucose in per branch of glucose 1-4 and 1-6 linkage held by glycosidic bonds
CELLULOSE
Cellulose occurs exclusively in plantsand it is a predominant contituent of plant cell wall cellulose is totally absent in animal body cellulose is composed of beta D glucose units linked by 1-4 linkage
CHITIN
Chitin is composed of N-Acetyl D-glucose amine units held together by (1-4)linkage glycosidic bonds it is a structural polysaccharides found in the exoskeleton of some invertebrates , insects and cristaceons
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