BY1-biological molecules-carbohydrates

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  • Created by: Izzy
  • Created on: 11-02-14 08:52
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  • Carbohydrates
    • Mono-saccharides
      • Building blocks for larger proteins. eg. glucose used to make starch, glycogen, cellulose.
      • (CH2O)n. Name determined by number of carbon atoms. Triose, hexose.
      • Ring structure when dissolved in water.
      • Source of energy in respiration. C-H bonds broken (releases energy.) Transferred to make ATP from ADP.
    • Disaccharides
      • Two monomers linked together. Glycosidic bond- elimination of water (condensation reactio)
      • Glucose + fructose= sucrose         Glucose + galactose= lactose
      • Used for transport and storage.
    • Testing for presence of sugars
      • Benedict's reagent used to test for presence of glucose
      • Equal volume reagent added to solution. Heat in boiling water bath.
      • Reducing sugar present: green-yellow-orange-brick red.
      • Some disaccharides are non reducing sugars eg. sucrose
        • Sucrose can only be detected if broken down by heating with HCL. Needs neutralising. Add Benedicts asn before.
    • Polysaccharides
      • Starch
        • alpha glucose. Amylose- linear, coils into helix. Amylopectin- branched, fits inside amylose.
        • Glucose storage. Glucose dissolves and would increase concentration. Water drawn in by osmosis.
        • Compact molecule
        • 1,4 linkages cause the chain to turn and coil
        • Glycogen (animal storage) Similar to amylopectin but more brached.
        • Readily hydrolysed to alpha glucose (soluble and transportable)
        • Test: Add iodine solution. Blue black.
      • Cellulose
        • Structural polysaccharide. In plant cell walls
        • Long parallel chains of beta glucose. H bond= structural stability.
        • Adjacent b glucose molecules rotated 180. H bonds between hydroxyl groups of adjacent chains.
        • 60-70 cellulose molecules become tightly cross linked to form bundles called microfibrils. These are held together in bundles (fibres)
        • Freely permeable
      • Chtitin
        • Found in insects.
        • Similar to cellulose but has amino acids added to form a mucopolysaccharide
        • Strong, waterproof, lightweight. Forms exoskeleton of insects.


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