Enzymes

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  • Enzymes
    • BIOLOGICAL CATALYST - speed up metabolic reactions in living organisms, and remain unchanged and reusable at the end of a reaction
      • Lowers the activation energy of a reaction (and hence speeds up reaction)
    • Intracellular
      • Metabolic pathway - a series of consecutive reactions, each step catalysed by a specific enyme
        • Metabolic disorder - enzyme deficiency
      • Catabolic - metabolites are broken down, and release energy
      • Anabolic - energy is used to synthesise larger molecules
      • e.g. Photosynthesis and respiration
      • Catalyse - protects cells from reactive O2 by breaking down hydrogen peroxide, H202
    • Extracellular
      • e.g. digestion in the small intestine
        • Trypsin - pancreas - digests protein into smaller polypeptides
        • Amylase - salivary glands and pancreas - digests starch into disaccharides
    • Active site
      • A specific area of the enzyme complementary to a substrate molecule
      • Tertiary structure
      • Determined by primary structure
    • Turnover number - number of reactions an enzyme can catalyse per second
    • Lock and Key theory
      • Substrate complementary to active site of enzyme
      • Does not explain how the ES complex is stabilised
      • Enzyme-substrate complex -- held together by temporary H bonds
        • Enzyme-product complex in anabolic reactions
    • Induced-fit theory
      • Active site changes shape slightly to more accurately conform to the shape of the substrate
    • Globular proteins
      • generally short polypeptides
  • - the role of enzymes in catalysing reactions that affect metabolism at a cellular and whole organism level - To include the idea that enzymes affect both structure and function.      (b) the role of enzymes in catalysing both intracellular and extracellular reactions       --To include catalase as an example of an enzyme that catalyses intracellular reactions and amylase and trypsin as examples of enzymes that catalyse extracellular reactions.

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