Cofactors, Coenzymes and Inhibitors

Question 1

What is a cofactor?

Answer 1

Non-protein inorganic molecules or ions that help the enzyme and substrate bind together more easily.

Question 2

What is an example of a cofactor in real life?

Answer 2

Chloride ions are cofactors for amylase.

Question 3

What doesn’t happen to cofactors in a reaction?

Answer 3

Changed or used up

Question 4

When does a cofactor get called a prosthetic group?

Answer 4

If the cofactor is permanently bound to an enzyme.

Question 5

What is an example of a prosthetic group in real life?

Answer 5

ZN2+ ions are a prosthetic group for carbonic anhydrase in red blood cells.

Question 6

What is a coenzyme?

Answer 6

Organic molecules that act as a second substrate.

Question 7

What happens to the coenzymes in a reaction?

Answer 7

They are changed by the reaction.

Question 8

What are coenzymes used for?

Answer 8

Carry chemicals between different enzymes.

Question 9

Are coenzymes used up in reactions?

Answer 9

No-they are continually recycled.

Question 10

Where are many coenzymes derived from?

Answer 10

Vitamins.

Question 11

What are inhibitors?

Answer 11

Molecules that can bind to an enzyme and prevent it from working.

Question 12

What are the two types of inhibitors?

Answer 12

-Competitive
-Non-competitive

Question 13

What are competitive inhibitors?

Answer 13

Molecules with a similar shape to the substrate that blocks the active site.

Question 14

What are non-competitive inhibitors?

Answer 14

Bind to an enzyme away from the active site which changes the shape of the enzyme so the substrate no longer fits.

Question 15

What is the other site called in non-competitive inhibitors?

Answer 15

Allosteric site

Question 16

When does an Allosteric Site occur?

Answer 16

When the non-competitive enzyme bonds away from the active site.

Question 17

What will be the rate of an enzyme controlled reaction with competitive inhibitors?

Answer 17

Substrate concentration will cause the rate of reaction to increase because the substrate is more likely to bind to the active site than the inhibitor.

Question 18

What will be the rate of an enzyme controlled reaction with non-competitive inhibitors?

Answer 18

Increasing the substrate concentration will not cause the rate of reaction to increase because the substrate can’t fit into the active site

Question 19

What are the further two types of inhibitors?

Answer 19

-Reversible
-Non-Reversible

Question 20

What is a reversible Inhibitor?

Answer 20

Can be removed from the enzyme because the bind to the enzyme via weak iconic or hydrogen bonds.

Question 21

What is a non-reversible inhibitor?

Answer 21

Can’t be removed from the enzymes because the bind the the enzyme via strong covalent bonds.

Question 22

What is End-product inhibition?

Answer 22

Term used for enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it.

Question 23

What does the end-product inhibition serve as?

Answer 23

As a negative feedback control mechanism for the reaction.

Question 24

In End-Product Inhibition, what is not made or wasted?

Answer 24

Excess products are not made and resources are not wasted.

Question 25

What is respiration?

Answer 25

A metabolic pathway resulting in the production of ATP

Question 26

How is glucose broken down?

Answer 26

1st-addition of 2 phosphate groups to the glucose molecule.

Question 27

What does the addition of the 2nd phosphate group result in?

Answer 27

The initial breakdown of the glucose molecule and is catalysed by PFK.

Question 28

Why does this enzyme cause ATP to regulate it’s own production?

Answer 28

This enzyme is completely inhibited by ATP.

Question 29

What happens when levels of ATP are high?

Answer 29

More ATP binds to the allosteric site on PFK, preventing the addition of the second phosphate group to glucose.

Question 30

When ATP levels are high, what happens to glucose and the ATP production?

Answer 30

Glucose is not broken down and ATP is not produced at the same rate.

Question 31

What happens as ATP is used up?

Answer 31

Less ATP binds to PFK and the enzyme is able to catalyse the addition of a second phosphate group to glucose. Respiration resumes, leading to the production of more ATP.

Question 32

What are Inactive Precursor enzymes?

Answer 32

Many enzymes are produced in an inactive form.

Question 33

Many enzymes are produced in inactive forms, particularly which enzymes?

Answer 33

Enzymes that can cause damage within the cells producing them
Tissues where they are released
Enzymes whose action needs to be controlled

Question 34

What often needs to happen to precursor enzymes?

Answer 34

A change in shape (tertiary structure) particularly active site, to be activated.

Question 35

How can this need for a change in shape alternatively be achieved?

Answer 35

By the addition of a cofactor

Question 36

Before a cofactor is added, what is the precursor protein called?

Answer 36

Apoenzyme

Question 37

After a cofactor is added and the enzyme is added what is it called?

Answer 37

Holoenzyme.

Question 38

How could a change in the tertiary structure be brought about?

Answer 38

By the action of another enzyme.

Question 39

A change in conditions could result in what?

Answer 39

A change in tertiary structure and activates a precursor enzyme.

Question 40

What are these types of precursor enzymes called?

Answer 40

Zymogens or proenzymes

Question 41

What happens when inactive pepsinogen is released into the stomach to digest proteins?

Answer 41

The acid pH brings around the transformation into the active enzyme pepsin.

Question 42

What does this adaptation do?

Answer 42

Protects the body tissues against the digestive action of pepsin.