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  1. 1. MACROMOLECULES Enzymes
  2. 2. Enzymes-Induced Fit Model Enzymes are protein molecules that act as biological catalysts They bind in a complementary manner with the reactant molecules or substrates to form an enzyme- substrate complex. They are specific in their action. i.e. one enzyme bonds with one substrate
  3. 3. Enzymes-Induced Fit Model They are not consumed in the reaction, but can be used over and over again Speed up reactions by lowering amount of energy needed for the reaction to occur
  4. 4. Activation Energy Without enzymes reactions would occur slowly. Chemical reactions involve the breaking and reforming of chemical bonds. For bonds to break an initial energy is required known as activation energy which will in turn release considerable free energy
  5. 5. Activation Energy
  6. 6. Enzyme practical - lipase This practical gives you a chance to:  investigate how lipase activity changes with temperature  consider how indicators can help us to follow chemical reactions. Procedure SAFETY: Keep the phenolphthalein solution away from naked flames. Wear eye protection and quickly rinse any splashes of enzyme solution or sodium carbonate from the skin.
  7. 7. Induced Fit
  8. 8. 2H2O2 2H2O + O2 Example, Hydrogen peroxide a substrate reacts with the enzyme catalase producing water and oxygen The active site is a flexible area so the enzyme and substrate induces a closer fit
  9. 9. Effects of pH and Temperature on Enzymes Most biological fluids have a narrow pH band between 6 and 8 and as a consequence most enzymes work optimally in that range. Changing pH can alter enzyme – substrate binding. High temperatures can the change active site and denature protein structure stopping substrate binding – above 500
  10. 10. Effect of Temperature on Pepsin Action of Pepsin and Trypsin
  11. 11. Other factors affecting action of Enzymes Inhibitors Chemical reactions that reduce action of enzymes. Competitive inhibitors block the substrate entering the active site by binding to it. They “mimic” the shape of the substrate. E.g. poisons such as DDT, arsenic and cyanide and penicillin blocks the active site which assists the creation of cell walls by many bacteria Non- competitive inhibitors bind elsewhere on the enzyme changing shape of enzyme reducing enzyme- substrate binding.
  12. 12. Cofactors Many enzymes require non-protein cofactors to assist their action. Cofactors bind to an active site or substrate before an enzyme can function Cofactors include copper, iron, zinc as well as many vitamins which are also known as co enzymes.
  13. 13. Physical and Chemical Factors affecting the binding of Enzymes
  14. 14. Assessed practical design Research What is rennin? Where is it normally found? What does rennin do to milk? What might you measure in this investigation? Due …….