Carbohydrates 2: Energy storage

HideShow resource information
View mindmap
  • Carbohydrates 2: Energy storage
    • Energy & structure
      • Glucose molecules contain a large number of bonds that can be broken to form simpler molecules
        • The braking of glucose into simpler molecules of water and CO2 in respiration releases energy, which is  used to make ATP
      • The breaking down of glucose in living organisms takes place in a series of many steps, each of which are driven by a specific enzyme
      • Animals & plants have enzymes that break alpha-glucose only, plant & animal enzymes cannot break down beta-glucose due to its different arrangement of the H and OH
        • So alpha-glucose can be respired whereas beta-glucose cannot
    • Carbohydrate polymers - stores of potential energy
      • Two alpha-glucose molecules bonded together form a disaccharide called maltose
        • The same condensation reaction can be carried out over and over again eventually forming amylose
          • The glycosidic bond between all the glucose subunits occurs between C1 of one molecule and C4 of the next, so is often called 1,4-glycosidic bond
            • The long chains of amylose coil into a spring because of the shape of the glucose molecules & the formation of the the glycosidic bonds
              • this makes amylose quite compact, iodine molecules can become trapped in the 'coils'of the spring
                • this causes iodine (in potassium iodine solution) to change colour from yellow/browm to blue/ black - starch test
      • not water soluible
    • Starch - the energy-storage polysaccharide in plants
      • Starch consists of a mixture of long, straight-chain amylose molecules & branched amylopectin
      • Starch in plants is a mixture of amylose and amylopectin - stored in chloroplasts & elsewhere in membrane-bound starch grains
      • Starch can be broken down to glucose molecules, which may then be respired to releasde energy
    • Glycogen - the energy-storage polysaccharide in animals
      • Glycogen is sometimes referred to as animal starch, it is identical to starch in that it is made up of alpha-glucose subunits; can also be broken down to release glucose to be respired
      • Differs from starch by having the 1-4 linked glucose chains in glycogen shorter with many more branches
      • Glycogen is more compact than starch & forms glycogen granules in animal cells e.g. liver & muscle cells
    • Features of the energy-storage molecules starch & glycogen
      • Dont dissolve - so  stored glucose dopes not affect water potential of the cell - vital in both plants & animals, as glucose stored as free molecules would dissolve & dramatically reduce water potential
      • Hold glucose molecules in chains so that they can easily be 'broken off' to provide glucose for respiration when required


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »