Polysaccharides

• what are polysaccharides made from?

  many glucose units joined together
• give 2 examples of polysaccharides?

  • glycogen
  • starch
  • cellulose
• what is glycogen made from?

  formed by the condensation of alpha glucose
• what is starch formed by?

  formed by the condensation of alpha glucose
• what are starch and glycogen both formed by?

  the condensation of alpha glucose
• What is cellulose formed by?

  the condensation of beta glucose
• what is the function of GLYCOGEN?

  The main energy storage molecule in animals
• What is glycogen formed from?

  Many molecules of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds
• why does glycogen have a large number of side branches?


  this means that energy can be released quickly as enzymes can work simultaneously on these branches
• how does glycogen maximise the amount of energy that it can store?

  it is a relatively large but compact molecule
• explain why glycogen is insoluble?

  it will not affect the water potential of cells and cannot diffuse out of cells
• give 3 properties of glycogen?

  • large number of side branches
  • relatively large but compact molecule
  • insoluble
• What does starch do?

  stores energy in plants
• what is starch made up of?


  starch is a mixture of two polysaccharides called amylose and amylopectin
• what do amylose and amylopectin make?


  starch
• what is amylose?

  An unbranched chain of glucose molecules joined by 1,4 glycosidic bonds

  • and as a result amylose is COILED and thus a very COMPACT MOLECULE STORING A LOT OF ENERGY
• What is amylopectin?

  A branched polysaccharide made up of glucose molecules joined by 1,4 and 1,6 glycosidic bonds

  • Due to the presence of many SIDE BRANCHES these can be ACTED ON SIMULTANEOUSLY BY MANY ENZYMES and thus BROKEN DOWN TO RELEASE ENERGY
• What are some properties of starch that make it suitable?

  • Insoluble
  • compact and
  • when it is hydrolysed the alpha glucose can be transported easily
• why is it suitable that starch is insoluble?


  so it will not affect water potential
• why is it suitable that starch is COMPACT?

  So a lot of energy can be stored in a small space and when it is hydrolysed the released alpha glucose can be transported easily
• what is the function of cellulose?


  it is a component of cell walls in plants
• what is cellulose composed of?

  long, unbranched chains of beta glucose which are joined by glycosidic bonds
• what are microfibrils?

  Strong threads which are made up of long cellulose chains running parallel to one another that are joined together by hydrogen bonds forming strong cross linkages
• what is cellulose important in?

  stopping the cell wall from bursting under osmotic pressure.

  • This is because it exerts inward pressure that stops the influx of water
  • This means that cells stay turgid and rigid, helping to maximise the surface area of plants for photosynthesis