The effect of temperature on the rate of enzyme action

• what does an increase in temperature do to the rate of reaction?

  it increases the kinetic energy of enzyme and substrate molecules and they collide with enough energy more often, increasing the rate of reaction
• how much does the rate of reaction increase by for each 10$^.$c rise?


  in general, the rate of reaction doubles for each 10$^.$c rise upto a particular temperature, about 40$^.$c for more enzymes
• what happens to enzymes above the 40$^.$c limit?

  • above this temperature, molecules have more kinetic energy but the reaction rate decreases as their increasing vibration breaks hydrogen bonds, changing the tertiary structure
  • this alters the shape of the active and the substrate will not fit
  • the enzyme is denatured, a permanent change in structure
• what happens to enzymes at low temperatures?

  • at low temperatures, the enzyme is inactivated as the molecules have very low kinetic energy
  • however, the shape is unchanged and the enzyme will work again if the temperature is raised
• what does denaturation mean?

  the permanent damage to the stucture and shape to a protein molecule (e.g. an enzyme molecule) due to, for example, high temperature or extremes of pH
• what does inactivation mean?

  reversible reduction of enzyme activity at low temperature as molecules have insufficient kinetic energy to form enzyme-substrate complexes
• what happens to the primary structure of an enzyme molecule when it becomes denatured?

  the order of amino acids (primary structure) is unaffected - it only loses higher levels of stucture
• what does this graph show?

  the effect of temperature on rate of reaction