Enzyme Action

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  • Enzyme Action
    • Enzymes lower the Activation Energy
      • This energy starts the reaction
      • This allows reactions to take place at lower temperature
        • Eg. Body Temperature
    • Enzyme Structure
      • Enzymes are globular proteins
      • The primary structure of the enzyme determines it's 3D shape
      • The small part of the enzyme which is functional is called the active site
    • How they work
      • The molecule the enzyme acts on is called the substrate
      • Substrate combines with the enzyme
        • Enzyme-substrate complex
      • Bonds around active site hold substrate in place
    • Models
      • Lock and Key
        • Each enzyme specific shape for each substrate
        • Rigid shape
      • Induced fit
        • The enzyme doesn't have a fixed shape
        • Moulds itself around the substrate whilst keeping basic shape
    • Measuring Enzyme Action
      • Measure time-course
        • How long event takes
      • Usually measure formation of products or disappearance of substrate
    • Factors which Affect Enzyme Action
      • Temperature
        • Higher temperature increases kinetic energy
          • More collisions
        • Once past optimum temp. weak bonds in enzyme break
        • Very high temp. can cause denature
      • pH
        • Measure of hydrogen ions concentration
        • Changes charges on amino acids around active site
        • Can break bonds in enzyme structure
      • Substrate concentration
        • First increases rate of reaction - more collisons
        • At a certain concentration, ROR stays constant - excess substrate to empty active sites
    • Inhibition
      • Competitive inhibitors
        • Binds to active site as have similar shape to substrate
        • Slows down rate of reactions
      • Non-competitive inhibitors
        • Attach themselves to a site which is not active
        • Changes the shape of active site
        • Not affected by substrate concentration


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