Topic 3 - Enzyme inhibition

Question 1

what is an enzyme inhibitor

Answer 1

a substance that slows down enzymes or stops them from working

Question 2

what are the 2 types of enzyme inhibition

Answer 2

reversible & irreversible

Question 3

what are the 2 types of reverse enzyme inhibition

Answer 3

competitive & non-competitive

Question 4

how does a competitive reversible inhibitor work

Answer 4

the inhibitor competes with the substrate by fitting into the active site instead of the substrate, preventing the formation of enzyme-substrate complexes

Question 5

what happens to the efficiency of competitive reversible inhibitors at high concentrations of substrate

Answer 5

the efficiency will decrease as there is a higher frequency of the substrates colliding with the enzyme’s active site than the inhibitor

Question 6

how does a non-competitive inhibitor work?

Answer 6

the inhibitor binds to the allosteric site, causing a change to the enzyme’s active site. This means that the active site is no longer complementary with the substrate, so the substrate cannot bind

Question 7

what happens to the efficiency of non-competitive reversible inhibitors at high concentrations of substrate

Answer 7

the efficiency of the inhibitor stays the same as the substrate levels cannot change the inhibitory effect

Question 8

explain the shape of the graph of a competitive inhibitor

Answer 8

• the inhibitors bind directly to the active site, so exist in direct competition with the substrate
• increasing substrate levels will increase the likelihood of the enzyme colliding with the substrate instead of the inhibitor
• the maximum rate of reaction of enzyme activity can still be achieved, although it requires a high substrate concentration

Question 9

explain the shape of the graph of a non-competitive inhibitor

Answer 9

• the inhibitors bind to an allosteric site, so do not exist in direct competition with the substrate
• increasing the substrate levels will not effect the level of inhibition caused by the non-competitive inhibitor
• the maximum rate of enzyme activity is reduced significantly

Question 10

how does irreversible inhibition work

Answer 10

the inhibitor combines with the enzyme by permanently covalent bonding to one of the vital groups. This causes the shape and structure to change, which affects the active site

Question 11

why is irreversible inhibition dangerous

Answer 11

it cannot be reversed, as the enzyme is permanently inactive

Question 12

give 3 examples of irreversible inhibitors

Answer 12

• mercury
• nerve gases used in chemical warfare
• many pesticides

Question 13

what is end-product inhibition

Answer 13

a feature of a chain of enzyme-controlled reactions in which a product of a late reaction in the series inhibits the enzyme controlling an earlier reaction