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  • GCSE BIOLOGY - digestive enzymes
    • enzymes are biological catalysts
      • speed up reactions and are not used up in them
      • they break down large, complex and insoluble molecules into small, simple and soluble molecules
    • human digestive enzymes
      • carbohydrase
        • substrate: carbs
        • product: sugars
        • location: mouth, pancreas, small intestine
      • protease
        • substrate: proteins
        • product: amino acids
        • location: stomach, pancreas, small intestine
      • lipease
        • substrate: lipids
        • product: fatty acids and glycerol
        • location: pancreas, small intestine
    • bile
      • bile is NOT an enzyme
        • it is an EMULSIFIER
          • it breaks down large globules of fat into smaller ones
            • this increases the surface area for lipase to work on and therefore speeds up digestion
      • bile is an alkaline substance
        • it neutralises any excess stomach acid at the beginning of the small intestine
          • this provides enzymes in the small intestine with their optimum pH
    • the lock and key theory
      • the active site
        • active site of the enzyme is complimentary to the substrate
          • at the optimum pH and temp, the enzyme and substrate fit perfectly together
          • the shape of the active site changes when we move away from the optimum temp
            • the active site become denatured and enzyme rate of reaction decreases
              • denatured means a permanent change to an enzyme as a result of extremes of pH and temp that stop it working
        • the active site is the region of an enzyme that binds it to its substrate
    • enzyme rate of reaction
      • factors affecting enzyme reaction
        • temperature
          • optimum
            • pH
        • substrate and/or enzyme concentration
          • high concentration
        • pH
        • surface area
          • more area for enzymes to digest
            • results in more collisions, more enzyme-substrate complexes formed, more product formed in the same amount of time
              • high concentration
              • optimum
      • enzymes are made of amino acids
        • a chain of amino acids twist together to form a 3D structure


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