1.9 Enzyme inhibition

Question 1

What are enzyme inhibiters

Answer 1

Substances that directly or indirectly interfere with the functioning of the active site of an enzyme, and so reduce its activity

Question 2

What is the difference between competitive and non competitive inhibiters

Answer 2

. Competitive inhibiters bind to the active site of the enzyme

. Non competitive inhibiters bind to the enzyme at a position other than the active site, so allosteric site

Question 3

Describe the shape of a competitive inhibiter and explain why this helps it do its job

Answer 3

. They have a molecular shape like a substrate which allows them to occupy the active site of an enzyme.

They therefore compete with substrates for the available active sites

Question 4

What effects competitive inhibiters

Answer 4

It’s the difference in the concentration of the inhibiter and the concentration of the substrate that determines the effect it has on enzyme activity.

If substrate concentration has increased, the effect of the inhibiter is reduced.
The inhibiter is not permanently bind to the active site so when it leaves another molecule can take its place (this could be a substrate or inhibiter molecule) depending on how much of each is present.

Eventually all substrate molecules will occupy an active site but the greater the concentration of inhibiter, the longer this will take

Question 5

An example of a competitive inhibiter occurs with an important respiratory enzyme that acts on succinate, that can be inhibited by another compound called malonate.

How does this happen

Answer 5

Malonate has a very similar shape to succinate so can inhibit the enzyme because it easily combines with the enzyme and blocks succinate from combining with the enzymes active site

Question 6

What are non competitive inhibitors and how do the work

Answer 6

. These attach themselves to the enzyme at a binding site which is not the active site

When attached, it alters the shape of the enzyme and thus its active site so substrate molecules can’t bind to it, and so the enzyme cannot function.

As the substrate and the inhibiter aren’t competing for the same site, an increase in substrate concentration doesn’t decrease effect of inhibiter.