Biology- Starch, Glycogen and Cellulose, plant cell structure

Starch, Glycogen and Cellulose, plant cell structure- basic notes for revision

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  • Created by: joti
  • Created on: 15-05-12 14:44

Starch and Glycogen

Polysaccharide found in small grains e.g. potato tubers

Made of    glucose linked with glycosidic bonds via condensation-> unbranched=tight coil (compacted)


Insoluble- doesn't draw water in via osmosis, doesn't diffuse out of cells, compact, when hydrolysed into    glucose, it can be easily transported--> never found in animal cells

Glycogen has shorter chains but is highly branched- main carb storage in animals as granules in the liver and muscles.

Smaller chains= easily hydrolysed than starch

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Made of    glucose-> positions of H and OH group are reversed

Straight unbranched chains, and run parallel to each other=> H bonds can form between chains for added structural support

Cellulose molecules are grouped=> microfibrils, arranged parallel=> fibres

Provides rigidity in plant cell walls and prevents cells from bursting (causes cells to become turgid by creating an inward pressure)

Maintains stems and leaves structure so maximum area is available for photosynthesis

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Plant cell structure

Leaf palisade cell=>long, thin, forms a continuous layer to absorb sunlight, lots of chloroplasts, large vacuole to push chloroplasts to edge of cell

 Chloroplasts=> Chloroplast envelope (double plasma membrane) , Grana (stacks of Thylakoids), Thylakoids contain Chlorophyll with tubular extensions to other Grana-> where 1st stage of photosynthesis takes place, and the Stroma (Fluid filled matrix, where 2nd stage of photosynthesis takes place)

They carry out photosynthesis because... Grana= large surface area so chlorophyll, enzymes and electrom carriers can attach to, Fluid od stroma has enzymes for 2nd stage of photosynthesis, Chloroplasts contain both DNA and Ribosomes so proteins are easily manufactured at will

Cell wall=>Made of cellulose and other polysaccharides, and the middle lamella cements adjacent cells together ==>They provide strength to stop the cell bursting, give strength to the plant as a whole and allows water to travel through the plant

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Thank you this was very helpful

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