AQA A Level Biology复习笔记1.4.7 Limiting Factors Affecting Enzymes: Temperature

Rate: Temperature

 

  • Enzymes have a specific optimum temperature – the temperature at which they catalyse a reaction at the maximum rate
  • Lower temperatures either prevent reactions from proceeding or slow them down:
    • Molecules move relatively slow
    • Lower frequency of successful collisions between substrate molecules and active site of enzyme
    • Less frequent enzyme-substrate complex formation
    • Substrate and enzyme collide with less energy, making it less likely for bonds to be formed or broken (stopping the reaction from occurring)

     

  • Higher temperatures speed up reactions:
    • Molecules move more quickly
    • Higher frequency successful collisions between substrate molecules and active site of enzyme
    • More frequent enzyme-substrate complex formation
    • Substrate and enzyme collide with more energy, making it more likely for bonds to be formed or broken (allowing the reaction to occur)

     

  • However, as temperatures continue to increase, the rate at which an enzyme catalyses a reaction drops sharply, as the enzyme begins to denature:
    • Bonds (eg. hydrogen bonds) holding the enzyme molecule in its precise shape start to break
    • This causes the tertiary structure of the protein (ie. the enzyme) to change
    • This permanently damages the active site, preventing the substrate from binding
    • Denaturation has occurred if the substrate can no longer bind
    • Very few human enzymes can function at temperatures above 50°C
      • This is because humans maintain a body temperature of about 37°C, therefore even temperatures exceeding 40°C will cause the denaturation of enzymes
      • High temperatures causes the hydrogen bonds between amino acids to break, changing the conformation of the enzyme

       

     

The-effect-of-temperature-on-an-enzyme-catalysed-reaction

The effect of temperature on the rate of an enzyme-catalysed reaction

 

转载自savemyexams

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