4.3 Enzyme inhibitors

Question 1

What can be used to activate an enzyme?

Answer 1

Cofactors

Question 2

What can be used to inactivate an enzyme?

Answer 2

Inhibitors

Question 3

What are inhibitors?

Answer 3

Molecules preventing enzymes from catalysing reactions

Question 4

What are the 2 types of enzyme inhibitors?

Answer 4

Competitive, non-competitive

Question 5

What are the 3 steps of competitive inhibition?

Answer 5

1. Molecule with a similar shape to substrate fits into active site
2. This blocks substrate entering active site, preventing enzyme from catalysing the reaction
3. Enzyme can’t carry out its function - inhibited

Question 6

Why are competitive inhibitors called competitive inhibitors?

Answer 6

Substrate and inhibitor in a solution compete with each other to bind to the enzyme’s active site.
This reduces amount of substrates entering active site and slows rate of reaction.

Question 7

Are competitive inhibitors reversible?

Answer 7

Most, yes - only bind temporarily to active site

Question 8

What effect do competitive inhibitors have on rate of reaction?

Answer 8

Reduce rate of reaction for a conc. of substrate, but don’t change enzyme’s Vmax

Question 9

Why don’t inhibitors lower the Vmax of enzymes?

Answer 9

If there are more substrates than inhitors, the Vmax can still be reached

Question 10

What are the x steps of non-competitive inhibition

Answer 10

1. Inhibitor binds to allosteric site
2. Binding causes change in tertiary structure so change in active site shape
3. Active site no longer complementary to substrate
4. Enzyme can’t carry out function - inhibited

Question 11

Why are non-competitive inhibitors called non-competitive inhibitors?

Answer 11

They don’t compete with substrates to bind to active site