Starch, glycogen and cellulose
- Created by: Laura
- Created on: 27-04-14 09:45
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- Starch, glycogen and cellulose
- Starch
- Starch is a poly-saccharide that is found in many parts of a plant
- Large amounts occur in seeds and storage organs
- Forms an important component of food and is the main energy source in most diets
- Made up of chains of alpha glucose linked by glycosidic bonds that are formed by condensation reactions
- Chain wound into a coil that makes the molecule very compact
- Main role of starch is an energy source which it is suited for
- It is insoluble - does not draw water into cell or diffuse out of cell
- It is compact so a lot can be stored in a small place
- Made of alpha glucose that is easily transported as well as readily used in respiration
- Glycogen
- Shorter chains and is highly branched
- Storage in animals not plants
- Stored mainly in the muscles and the liver cells
- Smaller chains means it is even more readily hydrolysed to alpha glucose
- Cellulose
- Made of beta glucose not alpha glucose
- H and OH group are reversed - each must be rotated 180 degrees to its neighbour to form glycosidic bonds
- Straight, unbranched chains
- These chains run parallel to each other allowing hydrogen bonds to form crosslinks between the chains
- Very strong due to the vast number of hydrogen bonds
- Cellulose molecules are grouped together to form micro-fibrils which are arranged in parallel groups called fibers
- Major component of plant cell walls and provides rigidity to the plant cell
- Also prevents plant cell from bursting as water enters by osmosis - exerts an inward pressure which stops any further influx of water
- Starch
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