Starch, Glycogen And Cellulose

STARCH:

• A polysaccharide found in many parts of a plant in the form of small grains.
• Forms an important component of food and is the major energy source in most diets.
• Made up of chains of alpha-glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions.
• The chains may be branched or unbranched.
• The unbranched chain is wound into a tight coil that makes the molecule very compact.
• Structure related to function:
  • It is insoluble and therefore doesn't affect water potential, so water is not drawn into the cells by osmosis.
  • Being large and insoluble, it does not diffuse out of cells.
  • It is compact, so a lot of it can be stored in a small space.
  • When hydrolysed it forms alpha-glucose, which is both easily transported and readily used in respiration.
  • The branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly.

GLYCOGEN:

• Found in animals and bacteria but never in plant cells.
• Very similar in structure to starch but has shorter chains and is more highly branched.
• Sometimes called animal starch because it is the major carbohydrate storage product of animals.
• In animals it is stored as small granules mainly in the muscles and the liver.
• The mass of carbohydrate that is stored is relatively small because fat…