Enzyme inhibition Flashcards
What are enzyme inhibitors?
Substances that directly or indirectly interfere with the functioning of the active site of an enzyme to reduce the RoR.
What are the 2 types of inhibitors?
- Competitive - binds to the active site.
- Non-competitive - binds to a position on an enzyme other than the active site.
Why does the competitive inhibitor occupy the active site?
Because they have a similar molecular shape to the substrate so they compete with the substrate for the available active site.
Show on a diagram what a competitive inhibitor do.
Draw on a piece of paper.
What determines the effect it has on the enzyme activity?
The difference in concentration of the inhibitor and substrate, because if there’s more substrate than the inhibitor, there are more chances that the substrate will react with an active site.
What is it good about the competitive inhibitor?
It does not permanently bound to the active site therefore when it leaves, another molecule can take its place. So competitive inhibitor does not stop substrates to react but it just reduces the RoR.
Give an example of a competitive inhibitor.
An important respiratory enzyme acts on succinate, but its inhibitor malonate can inhibit the enzyme because it has a very similar molecular shape to succinate.
What is a non-competitive inhibitor?
A non-competitive inhibitor attaches themselves to the enzyme at a binding site that is not the active site.
What is the difference between a competitive inhibitor and a non-competitive inhibitor?
- Non-competitive inhibitor attaches to a binding site permanently and the action is irreversible.
- Competitive inhibitor attaches to the active site temporarily and it’s a reversible reaction.
What happens to the substrate when a non-competitive inhibitor binds to the enzyme?
The substrate can no longer occupy the active site because the whole shape of the enzyme has changed due to the non-competitive inhibitor, therefore, the shape of the active site is no longer complementary to the substrate.
Why an increase in substrate does not decrease the effect of the inhibitor?
Because the substrate and the inhibitor are not competing for the same binding site so it does not have an effect.
Explain this example of negative feedback.
Substrate / (Enzyme A) —-) stage 1 / (Enzyme B) —-) Stage 2 / (Enzyme C) —-) End product.
The end product, for example, inhibits enzyme A, when the rate of end product goes above normal, there’ll be more inhibition to enzyme A, therefore the whole chain’s RoR will decrease and there’ll be less end product formed which means less inhibition for enzyme A which then will allow an increase of RoR and more end products will be produced and the whole process repeats.
What is an end product inhibition?
When the concentration of any chemical can be maintained relatively constant, this type of inhibition is usually non-competitive.
