Starch, glycogen, cellulose

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Where is starch found?
Found in grain form in plants. Large volumes in seeds or storage organs like potato tubers
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What is the role of starch?
Important component of foods, major energy source in the diet
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What is the structure of Starch?
Made up of long alpha glucose monosaccharide chains - made into a polysaccharide by condensation reactions, linked by glycosidic bonds. Result is an unbranched chain, tight helical coil for compact storage
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Why is starch suited to its storage role?
Insoluble - doesn't diffuse easily out of cells, doesn't allow water to enter cells by osmosis. Compact, a lot of starch stored in one small place. When hydrolysed, easily used as a-glucose for transport/respiration
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Where is glycogen found?
In animal cells, grain form in muscles and liver. Not in plant cells
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What is the role of glycogen?
Major carbohydrate storage product of animals
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What is the structure of glycogen?
Highly branched, shorter chains than starch
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How is glycogen adapted to its role?
Shorter chains than starch, more easily hydrolysed. Insoluble - doesn't diffuse out of cells or draw water in. Compact - a lot of glycogen stored in a small space.
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Where is cellulose found?
In cell walls in plants
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What are the roles of cellulose?
Component of plant cell walls, keeps cell/plant turgid, maintains stems, stops cell bursting/osmotic water entry, provides rigidity/mechanical support
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Structure of cellulose?
Straight, unbranched chains of beta glucose, alternate glycosidic bonds create cross linkages for strength with hydrogen bonds, very strong - run parallel and join up adjacent groups. Forms microfibrils and thus fibres.
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How is cellulose adapted for its role?
Major component of cell wall - stops cell bursting by exerting inward pressure and stops influx of water, plant cells remain turgid and push against each other for rigidity, maintains stem in a turgid state to provide max SA for photosynthesis
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Card 2

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What is the role of starch?

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Important component of foods, major energy source in the diet

Card 3

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What is the structure of Starch?

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Card 4

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Why is starch suited to its storage role?

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Card 5

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Where is glycogen found?

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