Between 0 degrees Celsius and the optimum, a rise of 10 degrees roughly doubles the rate of an enzyme catalysed reaction because
Correct answer: D. molecules move faster, so enzyme and substrate collide more often and with more energy
- 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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About Factors Affecting Enzyme Action
Enzyme activity changes with temperature, pH, substrate concentration and enzyme concentration because these factors affect molecular collisions and the active site. Questions also examine optimum conditions, denaturation and inhibition, while distinguishing a fall in activity caused by unsuitable conditions from permanent enzyme damage.
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