Cell Structures and Energy Storage


Cellulose is used in plant cell walls - provides rigidity

  • Made up of the monomer beta-glucose, meaning the hydrogen on carbon1 is below the ring
  • To form a chain each monomer must be rotated 180 degrees compared to it's neighbour to form a glycosidic bond
  • The chains are straight and unbranched which run parallel to each other
  • Hydrogen bonds form cross-linkages to add strength
  • Cellulose molecules grouped to form microfibrils, which are grouped in parallel to form fibres
  • Fibres layer on top of each other, each layer a different direction to the adjacent

Prevents osmotic lysis - exerts inward pressure, making cell turgid

The turgid plant cells increases the surface area for photosynthesis

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Used in energy storage in plants. Gets energy from glucose. Stores excess glucose as starch. When it needs the energy it breaks down the starch to release glucose.

  • Made up of the monomer alpha-glucose, meaning the hydrogen on carbon1 is above the ring
  • The monosaccharides are linked by glycosidic bonds formed by condensation reactions
  • Monomers form an unbranched chain which then coils into a helix - makes molecule compact

Related to function:

  • Is insoluble - doesn't draw water into cells via osmosis, prevents osmotic lysis and does not diffuse easily out of cells
  • Is compact - helix means a lot can be stored in a small place
  • When hydrolysed, forms alpha-glucose - is easily transported and used in respiration

Starch can be identified using iodine solution which it turns blue

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Used for enegy storage in animals

  • Made up of the monomer alpha-glucose, meaning the hydrogen on carbon1 is above the ring
  • Similar to starch but it's chains are shorter and more branched
  • Is stored as granules mainly in muscles and liver
  • The monomers coil to make molecule compact
  • The monomers form highly branched short chains so are hydrolysed more readily to produce alpha-glucose
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