Polysaccharides Polysaccharides

Polymers made of 100’s of monosaccharide units (MUs) A condensation reaction occurs between each MU and are held together with glycosidic bonds Molecules can be branched or unbranched Are insoluble and not sweet to taste Storage polysacs are folded to give compact molecules Structural polysacs are coiled or straight chained

Polysaccharides Starch: plant storage Glycogen: animal storage Cellulose: structural support

Starch Main carbohydrate food reserve in plants A polymer made up of many a glucose molecules held together by GLYCOSIDIC BOND Made of two compounds – amylose and amylopectin

Amylose Long chains of a glucose molecules linked by 1,4 glycosidic bonds Chains are coiled to form a spiral held in place by hydrogen bonds

Amylopectin Long chains of a glucose molecules linked by 1,4 glycosidic bonds Has some 1,6 glycosidic linkages giving it a branched structure

- no affect on osmotic balance of cell What makes starch a good food store? Compact for storage Insoluble - no affect on osmotic balance of cell Readily converted into sugar many side branches

Glycogen similar to amylopectin, made up of chains of a glucose But has many more 1,6 glycosidic side branches

Function Very compact storage molecule found in mammalian liver (and muscles) Increased branching allows for quick hydrolysis to release glucose Means very quick energy release

Cellulose Made up of long, unbranched chains of b glucose Individual chains are linked to each other by hydrogen bonds Overall structure is of long, strong microfibrils These form layers at different angles to each other, giving high tensile strength

CELLULOSE b glucose O HO OH H O HO OH H O HO OH H H OH O O HO OH H O

Function Structural polysaccharide in plants Cellulose cell walls provide high tensile strength to plant cells H-bonds prevent water entering the molecule Makes it resistant to hydrolysis from enzymes