Carbohydrates

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  • Carbohydrates
    • Monosaccharides
      • 3 Carbon atoms - TRIOSE SUGARS e.g glyceraldehyde
        • C3H6O3
        • function: found as intermediates in photosynthesis and respiration
        • made during the build up of glucose during photosynthesis + the breakdown of glucose during respiration
      • monomers which make up the larger carbohydrates
      • 5 carbon atoms - PENTOSE SUGARS
        • RIBOSE
        • DEOXYRIBOSE (1 oxygen has been taken out)
        • Function: forms part of nucleic acids (DNA + RNA molecules) + makes ATP (molecules that provide energy) during respiration
        • C5H10O5
      • 6 carbon atoms - HEXOSE SUGARS e.g glucose, fructose, galactose
        • can be a straight chain or a ring shaped molecule
        • Glucose has 2 isomers - alpha glucose + beta glucose
        • C6H12O6
    • Disaccharides
      • Formed by joining 2 hexose sugars = condensation reaction (involves removal of water).
        • Disaccharides are broken down into component monosaccharides by HYDROLISIS reactions (adding a water molecule)
          • New bond is formed = glycosidic bond
            • Glycosidic bond because the bond is formed between C1 and C4
      • New bond is formed = glycosidic bond
        • Glycosidic bond because the bond is formed between C1 and C4
    • Polysaccharides
      • Starch
        • Function = storage carbohydrate in PLANTS
          • compact  + can be stored in a small space
        • Made up of alpha glucose + has 1,4 glycosidic bonds
        • insoluble  (doesn't change the water potential of cells) + forms starch granules inside plant cells
        • Not a pure substance = mixture of AMYLOSE  + AMYLOPECTIN
          • Amylose = chain coils into helix (held by hydrogen bonds). Only 1,4 glycosidic bonds
          • Amylopectin = branched structure with 1,6 glycosidic bonds where it branches (as well as 14 bonds)
        • Easily hydrolised to alpha glucose which is soluble and can be transported to where the energy is needed
      • Glycogen
        • Alpha glucose molecules + storage carbohydrate in ANIMALS
          • Very branched = compact storage
        • Easily hydrolised to alpha glucose which is soluble and can be transported to where the energy is needed
        • insoluble  (doesn't change the water potential of cells) + forms starch granules inside plant cells
      • Cellulose
        • Beta glucose + structural carbohydrates in plant cell walls
        • chains linked together, alternate molecules are upside down
          • Allows hydrogen bonds to form between the molecules + other chains = making it stable + strong
          • Keeps the molecules straight + cable-like = good at resisting tension         Also makes a straight chain
        • chains linked together to form microfibrils
          • 60 - 70 cellulose molecules become cross-linked
      • Chitin
        • Beta glucose + structural polyhydrates
        • long-chain polymer of N-acetylglucosamine (beta glucose)
          • main component of cell walls of fungi, exoskeletons of athropods (crustaceans + insects)
        • Molecules are rotated 180 degrees + long parallel chains are linked by hydrogen bonds to form microfibrils
          • Strong + firm = supports body tissues
        • glucosamine - glucose in which 1 OH is replaced by a Nitrogen containing group

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