Structure
Starch - made up of amylopectin and amylose
Amylose is made up of alpha glucose with 1,4 glycosidic
bonds. It forms an unbranched chain that is right handed helix
Amylopectin is made up of alpha glucose with 1,4 and 1.6 glycosidic bonds. It forms a branched chain which is not a helix
source
Function
Starch is used as energy storage in PLANTS. Starch is unreactive and insoluble. This is because most of the OH that forms hydrogen bonds project inwards making starch unreactive so it can not diffuse out of the cell. Therefore starch is suitable for plant storage.
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Glycogen
Glycogen - made up of alpha glucose with 1,4 and 1,6 glycosidic bonds. It forms a branched chain which is more branched than amylopectin
source
Function
Glycogen is used as energy storage in animals. It is more soluble than starch because it has more 1,6 glycosidic linkages than starch. It is suitable as animal carbohydrate storage because it can be readily hydrolyzed to glucose when needed and because they is branching it is compact
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Cellulose
Structure
Cellulose - made up of beta glucose with 1,4 glycosidic bonds. It forms an unbranched straight chain. In cellulose the beta glucose are arranged alternately at 180 degrees to each other. Many OH groups form on both sides of the straight chain and form hydrogen bonds with each other. When many hydrogen bonded cellulose molecules come together a microfibril is formed which is strong. These microfibrils then criss-cross in the plant cell wall to give more strength
Function
Cellulose is used for making cell walls in plants. It is insoluble and unreactive so can not be hydrolyzed because it has no 1,6 glycosidic bonds. It is suitable as a structural molecule because it forms a straight chain which hydrogen bonds with each other to form microfibrils. The microfibrils then criss cross. These properties give cellulose strength
