Carbohydrates

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  • Created by: kim.a.r
  • Created on: 24-03-14 15:00
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  • Carbohydrates
    • Monosaccharides
      • Have a general formula CH2O
      • Glucose exists as two isomers
        • Alpha Glucose
        • Beta Glucose
      • Function: a source of energy in respiration. C-H bonds broken to release energy
      • Function: act as building blocks for larger molecules
    • Disaccharides
      • 2   monosaccharide units linked together with the formation of glycosidic bonds and the elimination of water
        • The elimination of water is also referred to as the condensation reaction
      • Glucose + Glucose = Fructose
      • Glucose + Fructose = Sucrose
      • Glucose + Galactose = Lactose
      • Function: For storage and transport
    • Polysaccharides
      • Starch
        • The main source of energy in cells. Starch is insoluble which prevents water being drawn into a cell
        • Starch is found in plant cells in the form of starch grains.
        • Starch is made up of alpha glucose and consists of two polymers, amylose and amylopectin. Amylose is linear whereas amylopectin is branched
        • The 1-4 linkages causes the chain to turn and coil. the main storage product in animals is called glycogen
        • Both starch and glycogen are readily hydrolysed to alpha glucose which is soluble and can be transported to areas in need of energy
      • Cellulose
        • A structural polysaccharide, it is present in the cell walls of plant cells
        • Long parallel chains of beta glucose cross-linked to each other by hydrogen bonds
        • The chain has adjacent glucose molecules  rotated by 180 degrees
        • The hydrogen bonds form between the hydroxyl groups of the adjacent parallel chains
        • Gives cellulose its structural stability
        • 60 to 70 cellulose molecules can become tightly cross-linked forming microfibrils
      • Chitin
        • A polysaccharide found in insects
        • Similar to cellulose but has amino acids added to it
        • It is strong, waterproof and light weight
        • Forms the exoskeleton of insects

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