4.4 : Cofactors, Coenzymes and Prosthetic Groups

Question 1

What is a cofactor?

Answer 1

A non-protein component that helps enzymes to carry out their functions.

They may transfer atoms or groups from one reaction to another in a multi - step pathway or they may form part of the active site of an enzyme.

Question 2

What is the source for inorganic cofactors?

Answer 2

Minerals

Question 3

What is the cofactor for amylase?

Answer 3

Chloride ion ( Cl-)

Question 4

What is a coenzyme?

Answer 4

If a cofactor is an organic molecule

Question 5

What is the source of coenzymes?

Answer 5

Vitamins

Question 6

What synthesises NAD?

Answer 6

Vitamin B3

Question 7

What vitamin makes coenzyme A?

Answer 7

Vitamin B5

Question 8

What are prosthetic groups?

Answer 8

They are cofactors - they are required by certain enzymes to carry out their function.

Question 9

What is the difference between prosthetic groups and other cofactors?

Answer 9

Some cofactors are loosely or temporarily bound to the enzyme protein to activate them, prosthetic groups are tightly bound and form a permanent feature of the protein.

Question 10

What is the prosthetic group of carbonic anhydrase?

Answer 10

zinc ions ( Zn 2+ )

Question 11

What are inactive precursor enzymes?

Answer 11

Enzymes that are produced in an inactive form, particularly enzymes that can cause damage within the cells producing them or to tissues where they are released, or enzymes whose action needs to be controlled and only activated under certain conditions.

Question 12

What is precursors activation?

Answer 12

Precursor enzymes often need to undergo a change in tertiary structure, particularly the active site to be activated.

This can be done by adding a cofactor.

Question 13

What are enzymes called before and after adding cofactors?

Answer 13

Before : apoenzyme

After : holoenzyme

Question 14

Apart from adding cofactors, how else can you change the tertiary structure?

Answer 14

Adding another enzyme ( e.g. Protease ) which cleaves certain bonds in the molecules.

A change in conditions , such as pH or temperature, sometimes changes the structure and activates a precursor enzyme. These types of precursor enzymes are called zygomens or proenzymes.

Question 15

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

Answer 15

The acid pH brings about the transformation into the active enzyme pepsin. This protects the body tissues against the digestive action of pepsin.