Between 0 degrees Celsius and the optimum, a rise of 10 degrees roughly doubles the rate of an enzyme catalysed reaction because

  • A. the enzyme molecules multiply
  • B. the activation energy of the reaction falls further
  • C. the active site changes shape to fit better
  • D. molecules move faster, so enzyme and substrate collide more often and with more energy

Explanation

Heat increases kinetic energy, so there are more successful collisions between enzyme and substrate per second and more enzyme substrate complexes form. Above the optimum this gain is overtaken by denaturation and the rate falls steeply, which is what gives the curve its sharp peak. The enzyme is a catalyst, so its number does not change during the reaction.

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