4.3 Enzyme Inhibitors

Question 1

Why is it important the cellular conditions are kept within narrow limits?

Answer 1

So that enzyme activity is not delayed

Question 2

Why is it important that reactions to not occur too fast?

Answer 2

Because it could lead to the build-up of excess products

Question 3

What can enzymes be activated with?

Answer 3

Cofactors

Question 4

What can enzymes be inactivated with?

Answer 4

Inhibitors

Question 4

What are inhibitors?

Answer 4

Molecules that prevent enzymes from carrying out their normal function of catalysis

Question 5

What are the two key types of inhibition?

Answer 5

Competitive and non-competitive.

Question 6

What happens between competitive inhibitors and substrate molecules?

Answer 6

They compete with each other to bind to the active site of an enzyme.

Question 7

Are most competitive inhibitors reversible or irreversible?

Answer 7

Reversible.

Question 8

How does a competitive inhibitor work?

Answer 8

-Inhibitor binds to the active site, competing with the normal substrate
-Substrate is unable to bind to the active site, preventing the reaction.

Question 9

Describe how a competitive inhibitor changes the rate of reaction, and explain why.

Answer 9

-It reduces the rate of a reaction for a given concentration of a substance, but it does not change the maximum rate of reaction of the enzyme it inhibits.
-If the substrate concentration is enough, there will be so much more substrate than inhibitor that the original maximum rate of reaction can still be reached.

Question 10

How does a non-competitive inhibitor work? (Simple answer)

Answer 10

It binds to the allosteric site, not the active site

Question 11

What is the name of the site that the non-competitive inhibitor binds to?

Answer 11

Allosteric site

Question 12

Describe how a non-competitive inhibitor works (long answer)

Answer 12

-Inhibitor binds to the enzyme at a location that is not the active site
-The binding of the inhibitor causes the tertiary structure of the enzyme to change, meaning the active site changes shape
-This results in the enzyme no longer having a complementary shape to the substrate, so it is unable to bind to the enzyme.
-The enzyme cannot carry out its function, and is inhibited.

Question 13

Describe how a non-competitive inhibitor changes the rate of reaction, and explain why.

Answer 13

-It decreases the rate of reaction permanently
-Increasing the concentration of enzyme or substrate will not overcome the effect of a non-competitive inhibitor.

Question 14

Is the binding of a non-competitive inhibitor reversible or irreversible?

Answer 14

Both.

Question 15

What is end-product inhibition?

Answer 15

The term used for enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it.

Question 16

What kind of system is an end-product inhibitor used in?

Answer 16

Negative-feedback loop. Excess products are not made, and resources are not wasted