4.2 - Factors Affecting Enzyme Activity

Question 1

How does temperature affect enzyme activity?

Answer 1

• In mammals the optimum enzyme temperature is 37^oC, as the temperature rises the molecules have more kinetic energy to collide more frequently
  
  • The molecules are more likely to have sufficient energy to overcome E_a
• At low temperatures, there is insufficient kinetic energy, leading to infrequent collisions
• If the temperature is too high the bonds of the 3^o structure vibrate too much and break, meaning the active site loses its shape so it is not specific to it’s substrate

Question 2

What is Q10?

Answer 2

• Temperature coefficient -
• How much the rate of reaction increases by per 10^oC temp rise
• For enzyme controlled reactions Q10 = 2 (means reaction rate double per 10 degrees C temp. rise)

Question 3

How does pH affect enzyme activity?

Answer 3

Enzymes are proteins affected by pH changes - change in [H⁺] changes R-group interactions affecting active site shape

Renaturation can occur - if the pH changes to optimum the shape of the active site can change again to its original shape. - If pH significantly alters, enzymes permanently denature.

Question 4

How does an increase in enzyme/substrate concentration affect rate of reaction?

Answer 4

• When substrate concentration increases - higher collision rate with enzyme’s active site - increasing rate of reaction until Vmax, but all active sites will be occupied so adding more substrate makes no difference due to limit of active sites.