Control of enzymes

Question 1

Factors affecting enzyme activity

Answer 1

Temperature 
pH
Concentration of substrate and product .
Availability of active sites 
Last two graphs are /—

Question 2

Ways of regulating enzyme activity

Answer 2

Controlling number of enzyme molecules produced by switching genes on and off
Keeping reactions in compartments
Driving the reaction in different directions using reversible steps.
Use of inhibitors

Question 3

3 types of inhibitors

Answer 3

Competitive, non competitive and feedback/end product

Question 4

How do enzyme inhibitors lower the rate of reaction?

Answer 4

Enzyme inhibitors reduce the rate of an enzyme catalysed reaction by interfering with the enzyme in some way. This effect may be permanent or temporary.

Question 5

Competitive inhibitors-

Answer 5

Competitive enzyme inhibitors work by having a
similar shape to the substrate molecule.
Competitive inhibitors bind at the active site, but remain unreacted since they have a different structure to the substrate, preventing the substrate from binding.
Fewer substrate molecules can bind to the active site so the reaction rate is decreased.

Question 6

How can the effect of competitive inhibitors be reversed

Answer 6

Yes - by increasing the substrate concentration, however eventually this won’t matter as the limiting factor will be the enzyme active site availability

Question 7

Non competitive inhibitors-

Answer 7

Non-competitive inhibitors bind to the enzyme but not in the active site. When the inhibitor binds it causes a change in the shape of the active site. This change in structure means that the substrate cannot bind thus the reaction
is not catalysed.

Question 8

Can effect of non competitive inhibitors be reversed by increasing concentration of substrate?

Answer 8

No, since the inhibitors do not compete with the substrate

Question 9

Feedback inhibitors

Answer 9

The final product itself acts
as an inhibitor, therefore this type of inhibition is also known as end-product inhibition.
The end-product binds to an allosteric site of an earlier enzyme, altering the shape of the active site, inhibiting this enzyme. This blocks the pathway and prevents further
synthesis of the end-product.

Question 10

Positives of feedback inhibitors

Answer 10

Saves energy as they don’t have to waste energy producing non-competitive inhibitors

Question 11

Multi-enzyme complexes

Answer 11

Since enzymes are often part of multi step pathways there are multi-enzyme complexes - grouping of enzymes