• 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 the rate of an enzyme-catalysed reaction