Retrieval exercise 6

Induced fit

• A substrate and its active site are not fully complementary to begin with

• When a substrate binds with an enzyme, it induces change in the enzyme structure

• The active site changes shape to become complementary 

• This puts strain on the substrate and distorts the bonds thus reducing the activation energy

Effect of high temperature

• As temperature increases, enzyme and substrate molecules gain more kinetic energy

• They collide more frequently

• So a greater number of enzyme-substrate complexes are formed

• Leading to an increased rate of reaction

Effect of pH

• A change in pH causes some of the hydrogen and ionic bonds that maintain the enzyme’s tertiary structure to break

• The shape of the active site changes

• No enzyme-substrate complexes can be formed

• The enzyme has been denatured

Competitive inhibitors

• Has a similar shape to that of the enzyme’s substrate

• It binds to the active site of the enzyme

• The active site is occupied and blocked

• Fewer enzyme-substrate complexes are formed and the rate of reaction is reduced

Non-competitive inhibitors

• Non-competitive inhibitors bind to some other region of the enzyme (allosteric site)

• This changes the tertiary structure so changing the shape of the active site

• The substrate cannot bind

• Fewer enzyme-substrate complexes are formed so reaction rate decreases