Enzyme Properties

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Effect of Temperature

  • a rise in temperature increases the kinetic energy of molecules so they collide more often 
  • this means the enzyme and substrate molecules come together more often = increase in rate of reaction
  • a rise in temperature causes hydrogen bonds to break, this changes the shape of the enzymes active site
  • the substrate fits less easily and so the rate of reaction is slowed 
  • the enzyme can become so disrupted it denatures and stops working all together 
  • this usually happens around 60 degrees
  • the optimum temperature can differ and is when the enzyme is working the fastest
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Effect of pH

  • each enzyme has an optimum pH at which it works the fastest
  • a change in pH reduces the effectiveness of the enzyme and may cause it to stop working all together 
  • a change in pH alters the charge of the amino acids that make up the active site, this means the substrate can no longer attach to the active site oin an enzyme-substrate complex 
  • a change in pH causes the bonds which make up the enzymes tertiary structure to break 
  • this means the enzyme changes shape and the substrate may no longer fit, the enzyme has been denatured 
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Effect of Substrate Concentration

  • if the amount of enzyme is kept constant and substrate is slowly added, the rate of reaction increases proportionally
  • at low substrate concentrations, the enzyme molecules only have a limited number of substrate molecules to collide with 
  • therefore the active sites are not working to full capacity 
  • if more substrate is added the active site gradually become filled until they are working as fast as they can 
  • the reaction reaches Vmax, its optimum rate of reaction 
  • after that an increase in substrate will have no effect because all the active sites are full  
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Competitive Inhibitors

  • have a molecular shape similar to the substrate 
  • this allows them to occupy the active site of the enzyme 
  • they compete with the substrate for available active sites 
  • if the substrate concentration is increased the effect of the inhibitor is reduced
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Non-Competitive Inhibitors

  • Non-competitive inhibitors attach themselves to a site that is not the active site 
  • the inhibitor alters the shape of the enzymes active site in such a way that the substrate will no longer fit, so the enzyme cannot function 
  • the substrate and the enzyme are not competing for the same site so an increase in substrate concentration does not effect the inhibitor 
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