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  • Enzymes
    • Biological catalysts
      • Speed up reactions by reducing activation energy
      • Recyclable- used multiple times
    • Types
      • Intra cellular- inside cell
      • Extra cellular- outside cell
    • Specificicitiy
      • Catalyse a reaction for only one specific substrate
      • Active site
    • Inhibition
      • Competitive inhibition
        • Generally temporary
        • Used to control enzyme reations
        • Competes for active site
          • Inhibitors obstruct active site = reduced rate of reaction
      • Non competitive Inhibition
        • doesn't compete for active site
        • Alters the tertiary structure
          • Alters the ionic, hydrophobic/ phillic, disulphide etc. bonds
        • permanent change
        • Primary structure changes shape
      • Reversible/ non- reversible inhibition
        • Strength of bonds between the enzyme and inhibitor
          • H bond =  weak = temporary
          • Covalent bonds = strong = permenant
      • Metabolic poisins
        • Cyanide, Malonate and Arsenic
          • Bond to respiratory  enzyme = respiration stops = cell dies
      • Drugs
        • HIV- RNA is injected into cell. Reverse transcriptase converts the RNA into DNA which then reproduces.
          • Drug- Inhibitor attaches to the enzyme reverse transcriptase = no viral reproduction
      • Cofactors/ coenzymes
        • attach to the enzyme and change active site for the better = cellular control of reaction by producing cofactors
          • Poison in Anti- freeze. Alcohol is a competitive inhibitor so prevents the Ethylene Glycol from being broken down into oxalic Acid which is highly poisonous
          • Penicillin- inhibits the enzyme transpeptidase which catalyses the formation of proteins in bacterial cell walls = weakens cell wall = can't regulate its osmotic pressure = cell bursts and is killed
    • Optimum conditions
      • Endothermic animals- self regulate body temp.
      • 37 Degrees Celsius
    • Limiting factors
      • Activity affected by temperature
      • Activity affected by pH
      • Concentration of enzymes
      • Concentration of substrates
      • Surface area
    • Uses
      • Heterotrophs
        • Breaking down larger molecules into smaller to extract nutrience
      • External digestion
        • Enzyme secreted on food which breaks it down into monomers. Organism then absorbs these.
      • Internal digestion
        • Enzymes mixed in as food passes through the digestive system
          • Extra cellular- released from cell onto food within digestive system
          • Inter cellular- Found in cytoplasm or attached to cell membrane. These enzymes are active inside the cell.
      • Protection
        • Defence mechanism- white blood cells (phagocytes) engulf bacteria and then digest them using lysosomal enzymes


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