Polysaccharide

• How are polysaccharide formed

  By condensation reactions between many glucose molecules (a-glucose for starch and glycogen, B-glucose for cellulose), this releases a molecule of water each time
• describe the structure of a glycogen molecules

  A polymer of a-glucose, joined by condensation reactions to make glycosidic bonds. It has a branched structure
• describe the structure of a molecule

  A polymer of a-glucose, joined by condensation reactions to make glycosidic bonds. It has a coiled and branched structure
• describe the structure of a cellulose molecule

  A polymer of beta glucose joined by condensation reactions to make glycosidic bonds. It has long, straight and unbranched chains.
• Describe the structure of cellulose

  A polymer of B-glucose, joined by glycosidic bonds. It has long, straight and unbranched chains, that can be joined together by Hydrogen bonding to produce microfibrils, and fibres.
• explain how the structure of glycogen is related to the function

  Glycogen is insoluble, so it doesn't affect the water potential of the cell. It is a highly branched polymer of a-glucose, so can quickly be hydrolysed by enzymes into glucose to provide a respiratory substrate. It is a large molecule, so cannot pass through the cell surtace membrane. It is highly branched so it is compact and many can fit into a small area.
• explain how the structure of starch is related to it’s function

  Starch is insoluble, so it doesn't affect the water potential of the cell. It is a highly branched polymer of a-glucose, so can quickly be hydrolysed by enzymes into glucose to provide a respiratory substrate. It is a large molecule, so cannot pass through the cell surface membrane. It is coiled so it is compact and many can fit into a small area.
• explain how the structure of cellulose Is related to the function

  Cellulose are long, straight, unbranched chains of B-glucose.

  These polymer chains get joined by hydrogen bonds to form microfibrils and fibres which provide rigidity and strength to the plant cell.
• what is the test for starch

  A solution of potassium iodide, add to the test sample. A colour change from orange to blue/black is positive.