4.3 Enzyme Inhibitors

Question 1

What is competitive inhibition?

Answer 1

• when a molecule has a similar shape to the substrate of an enzyme and can fit into the active site enzyme
• this blocks the substrate from entering the active site, preventing the enzyme from catalysing the reaction
• the enzyme is inhibited
• this is reversible

Question 2

How does competitive inhibition affect the rate of reaction?

Answer 2

• reduces rate of reaction
• but does not lower Vmax
• (if the substrate conc. is increased, there will be more substrate than inhibitor, and the original Vmax can be reached)

Question 3

What is non-competitive inhibition?

Answer 3

• when the inhibitor binds to the allosteric site
• this causes a change in the tertiary structure of the enzyme, meaning that the active site changes shape
• active site and substrate are no longer complementary to each other
• enzyme cannot carry out its function and is inhibited
• is reversible or irreversible

Question 4

How does non-competitive inhibition affect the rate of reaction?

Answer 4

• Vmax is lowered
• rate is lowered
• changing the conc. has no effect

Question 5

What is end-product inhibition?

Answer 5

When the product of a reaction acts as an inhibitor to the enzyme that produces it

Question 6

How is end-product inhibition a negative feedback mechanism?

Answer 6

• excess products will not be made and resources will not be wasted