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 reversible enzyme inhibition

Answer 3

competitive & non-competitive

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

explain the shape of the graph of a competitive inhibitor

Answer 6

• 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 7

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

Answer 7

• 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 8

why is irreversible inhibition dangerous

Answer 8

it cannot be reversed, as the enzyme is permanently inactive

Question 9

give 3 examples of irreversible inhibitors

Answer 9

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

Question 10

what is a reversible inhibitor

Answer 10

an inhibition of the reaction of an enzyme by an inhibitor that does not permanently affect the functioning of the enzymes and can be removed from the enzyme.

Question 11

what is an irreversible inhibitor

Answer 11

an inhibition of the reaction of an enzyme that is permanent and cannot be undone

Question 12

what are competitive inhibitors

Answer 12

the inhibition in which the inhibitor molecule is similar in shape to the substrate molecule and competes with it for the active site of the enzyme

Question 13

what are non-competitive inhibitors

Answer 13

the inhibition in which the inhibitor does not compete for the active site, but forms a complex with the allosteric site, that changes the shape of the active site so it can no longer catalyses the reaction

Question 14

what are regulatory enzymes

Answer 14

enzymes that have a site separate to the active site where another molecule can bind to have an activating or inhibitory effect

Question 15

what is end-product inhibition

Answer 15

a control system in many metabolic pathways in which en enzyme at the beginning of the pathway is inhibited by one of the end products of the reaction