Enzymes IBDP HL


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Enzymes IBDP HL

  1. 1. Enzymes are protein molecules that are able to catalyse a biological reaction.
  2. 2.  Each type of enzyme is highly specific for only one type of a reaction With the use of an enzyme the rate of a particular reaction can increase by a factor greater than 108 They work by providing an alternative pathway with a lower activation energy More reactant molecules then have the necessary minimum activation energy
  3. 3.  The specificity of the enzyme depends on their tertiary and quaternary structure. The substrate (reactant molecule) binds to a part of the enzyme known as the active site The active site is able to change shape allowing the substrate to fit effectively and this is known as the induced fit theory
  4. 4.  Inhibitors are substances that slow down the rate of an enzyme catalysed reaction Competitive inhibitors resemble the substrate in shape but they are unable to react They occupy the active site making it less accessible to the substrate As the concentration of the substrate molecules increases the effect of the competitive inhibitors decreases
  5. 5. Competitive inhibition
  6. 6.  Non-competitive inhibitors bind to the enzyme but not to the active site The enzyme then changes shape and the substrates are no longer able to bind With this type of inhibitor increasing the concentration of the substrate molecules will have no effect as the non-competitive inhibitors don’t bind to the active site
  7. 7. Non-competitive inhibition
  8. 8.  At low substrate concentrations the rate of the reaction is proportional to the concentration of the substrate At high substrate concentrations the rate of the reaction reaches a maximum point known as Vmax This means that that at low substrate concentrations there are enough active sites for the substrates to bind and react When all the active sites are used the enzyme is not able to work any faster
  9. 9.  This constant Km is the concentration of the substrate at half of the Vmax It is always the same for a particular enzyme with a particular substrate It indicates whether the enzyme functions appropriately at low substrate concentrations or whether high substrate concentrations are needed for the efficient catalysis Lower Km → more efficient enzyme
  10. 10. Say That Again Pleasehttp://www.youtube.com/watch?v=q94TCTSXyv8&context=C47b5c79ADvjVQa =
  11. 11. Competitive vs Non-competitive Competitive inhibitor  Non-competitive Blocks active sites  Enzyme changes shape Same Vmax  Smaller Vmax Larger Km  Same Km
  12. 12.  An increase in temperature at first increases the rate of the reaction until the optimum temperature is reached (usually 40°C) Until then more reactants posses the necessary activation energy to react After the optimum temperature is reached the enzyme starts to denaturate as the bonds holding the structure together break At certain pH values there is a change in the charge of the amino acid which affects the bond and alters the structure of the enzyme making it inactive
  13. 13.  Heavy metals “poison” the enzyme They react with the –SH group and replace the hydrogen atom with a heavy metal atom, or ion altering once more the structure of the enzyme
  14. 14. Effect of temperature and pH on rate of enzyme activity