Enzymes

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Enzymes

  1. 1. Enzymes - VIP molecules. Mr Mark Gretgrix Wedderburn College
  2. 2. Description/ Definition <ul><li>Biological catalysts, made of protein, coded for by DNA. </li></ul><ul><li>allow reactions to occur more easily </li></ul><ul><li>help cells perform reactions that would normally occur very slowly, or not at all </li></ul>
  3. 3. <ul><li>do not get changed during reaction, they can be recycled </li></ul><ul><li>found in cytoplasm and in various organelles </li></ul><ul><li>can be secreted and work outside the cell </li></ul><ul><li>are involved in breakdown and synthesis </li></ul>
  4. 4. Examples: <ul><li>Urease - catalyses the breakdown of urea </li></ul><ul><li>Catalase - breakdown of hydrogen peroxide </li></ul><ul><li>Polymerase - DNA synthesis </li></ul>
  5. 5. Cell Metabolism. <ul><li>Refers to all the chemical reactions in a cell. </li></ul><ul><li>Involves complex sequences of reaction with each one controlled by an enzyme. The product of one reaction becomes the reactant of the next reaction. </li></ul>
  6. 6. <ul><li>By controlling the availability of enzymes, cells can control which chemical reactions will take place at any one time. </li></ul>
  7. 7. Mode of Operation Enzymes act to orient the reactant/s so that they behave exactly as required for the reaction to occur.
  8. 8. Substrate Product Eg a decomposition reaction:
  9. 9. Sucrose  Glucose + fructose:
  10. 10. <ul><li>The enzyme has a specific shape, it can only be used to catalyse one type of reaction. </li></ul><ul><li>The site at which the reaction takes place in the enzyme is called the ACTIVE SITE. </li></ul>
  11. 11. Rate of Reaction - depends on: <ul><li>Temperature </li></ul><ul><li>amount of reactants and products present </li></ul><ul><li>pH </li></ul><ul><li>presence of other substances </li></ul>
  12. 12. Temperature: <ul><li>As temperature increases the number of collisions between molecules increases. </li></ul><ul><li>--> increases enzyme activity </li></ul>
  13. 13. <ul><li>As temperature decreases the number of collisions between molecules decreases. --> decreases enzyme activity </li></ul>
  14. 14. <ul><li>At higher temperatures the protein structure ‘overheats’, the enzyme is ‘denatured’, the active site cannot function. --> decrease in enzyme activity </li></ul>
  15. 16. Amount Reactants/ Products - enzymes work in equilibrium reactions <ul><li>Enzymes operate to create a balance between reactants and products </li></ul><ul><li>To increase enzyme activity reactants need to be available and products need to be removed. </li></ul>
  16. 18. Amount of enzyme present: <ul><li>An increased amount of enzyme will increase the reaction rate. </li></ul><ul><li>This will be affected by the concentration of the substrate available. </li></ul>
  17. 20. pH <ul><li>Affects hydrogen bonding in the protein which affects the active site </li></ul><ul><li>Each type has its optimal pH, activity decreases away from this value </li></ul>
  18. 22. Other substances <ul><li>Block the active site by binding to it. eg. poisons </li></ul><ul><li>Alter the shape of the active site by binding onto another part of the enzyme </li></ul>
  19. 23. Co-enzymes <ul><li>Small molecules needed to help the enzymes in their activity </li></ul><ul><li>eg. Some vitamins, trace elements </li></ul>

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