Module 2 Section 4 - Cofactors and Enzyme Inhibition

Question 1

What are cofactors

Answer 1

Substances that are non protein that are bound to enzymes to allow them to work

Question 2

Some cofactors are

Answer 2

Inorganic molecules or ions

Question 3

How do cofactors work

Answer 3

They work by helping the enzyme and substrate to bind together

Question 4

Do cofactors participate in the reaction

Answer 4

No, so they aren’t used up or changed in any way by the reaction

Question 5

What are coenzymes

Answer 5

Cofactors that are organic molecules

Question 6

Do coenzymes participate in reactions

Answer 6

Yes, they participate in reactions and are changed by it

Question 7

Coenzymes often act as….

Answer 7

Carriers, moving chemical groups between different enzymes.

Question 8

Are coenzymes recycled

Answer 8

Yes, they are continually recycled during this process - vitamins are often sources of coenzymes

Question 9

What is a prosthetic group

Answer 9

A cofactor that is tightly bound to the enzyme

Question 10

How can enzyme activity be prevented

Answer 10

By enzyme inhibitors

Question 11

What are enzyme inhibitors

Answer 11

Molecules that bind to the enzyme that they inhibit

Question 12

Enzyme inhibition can be either

Answer 12

Competitive
Non competitive

Question 13

What is a competitive inhibitor

Answer 13

Molecules that have similar shape to that of the substrate molecule

Question 14

Why is it called competitive

Answer 14

Because they compete with the substrate molecules to bind to the active site, but no reaction takes place. They block the active site so the substrate doesn’t fit in

Question 15

How much the enzyme is inhibited depends …

Answer 15

On the relative concentrations of the inhibitor and the substrate

Question 16

If there’s high concentration of the inhibitor…

Answer 16

It’ll take up nearly all the active sites and hardly any of the substrate will get to the enzyme - decreasing rate of reaction

Question 17

If there’s a higher concentration of substrate….

Answer 17

Then the substrates chances of getting to an active site before the inhibitor increase meaning increasing substrate will increase rate of reaction

Question 18

Where do non competitive inhibitor molecules bind to

Answer 18

The allosteric site (away from the active site)

Question 19

Why does the non competitive inhibitor binding to the allosteric site cause

Answer 19

Causes the active site to change shape - so the substrate molecule no longer fits

Question 20

Why are non competitive inhibitors called non competitive

Answer 20

Because they don’t compete with the substrate molecules to bind to the active site because they are a different shape

Question 21

What difference will Increasing the substrate make to the rate of reaction on non competitive inhibition

Answer 21

Enzyme activity will still be inhibited

Question 22

Inhibitors can be ….

Answer 22

Reversible
Non-Reversible

Question 23

What does the reversibility of inhibitors depend on

Answer 23

The strength of the bonds between the enzyme and the inhibitor

Question 24

What is the reversibility if the bonds between the enzyme and inhibitor is strong covalent bonds

Answer 24

Non reversible, because the inhibitor can’t be removed easily

Question 25

What is the reversibility if the bonds between enzyme and inhibitor is weak hydrogen or ionic bonds

Answer 25

Reversible, the inhibitor can be removed

Question 26

Some drugs and metabolic poisons are….

Answer 26

Enzyme inhibitors

Question 27

Some medical drugs are enzyme inhibitors e.g.

Answer 27

Some Antiviral drugs - reverse transcriptase inhibitors
Some antibiotics - penicillin

Question 28

Metabolic poisons are often enzyme inhibitors e.g.

Answer 28

Cyanide
Malonate
Arsenic

Question 29

What are metabolic pathways regulated by

Answer 29

End-product inhibition

Question 30

What is a metabolic pathway

Answer 30

A series of connected metabolic reactions. The product of the first reaction takes part in the second and so on. Each reaction is catalysed by a different enzyme

Question 31

What is product inhibition

Answer 31

Enzymes that are inhibited by the product of the reaction they catalyse

Question 32

What is end-product inhibition

Answer 32

When the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway

Question 33

What is the reversibility of product and end-product inhibition

Answer 33

Reversible, so when the level of the product starts to drop, the level of inhibition will start to fall and the enzyme can start to function again - this means more product can be made

Question 34

Enzymes are sometimes synthesised as

Answer 34

Inactive precursors in metabolic pathways to prevent causing damage to cells e.g. proteases.

Question 35

Part of the precursor molecules…

Answer 35

Inhibits it’s action as an enzyme, once it is removed the enzyme becomes active