Cofactors and coenzymes

Question 1

What is a cofactor?

Answer 1

A non-protein which, alongside a protein, enzymes consist of

Question 2

How do cofactors bind?

Answer 2

Loosely to the enzyme or form part of the active site to activate them

Question 3

What do cofactors do?

Answer 3

They help the enzyme to carry out it is function by transferring atoms or groups from one reaction to another in a metabolic pathway

Question 4

What are the two types of cofactors?

Answer 4

Organic or inorganic

Question 5

How are inorganic cofactors taken in?

Answer 5

Through the diet as mineral ions

Question 6

What are examples of inorganic cofactors?

Answer 6

Zinc, iron, calcium and chloride ions

Question 7

What is an example of how inorganic cofactors are used?

Answer 7

Amylase, which breaks down starch to maltose, needs the chloride ion to help form the correct shape of the active site

Question 8

What is another name for organic cofactors?

Answer 8

Coenzymes

Question 9

Where are coenzymes derived from?

Answer 9

From vitamins such as Vitamin B3 which is used to synthesis the coenzyme NAD (nicotinamide adenine dinucleotide)

Question 10

What does NAD do?

Answer 10

It transfers hydrogen atoms between molecules in the reactions in respiration

Question 11

How is NAD needed?

Answer 11

The enzyme alcohol dehydrogenase needs NAD to transfer hydrogen in the conversion of ethanal to ethanol in anaerobic respiration

Question 12

What is an example of a vitamin used to make a co-enzyme?

Answer 12

Vitamin B5 is used to make co-enzyme A which is essential in the breakdown of fatty acids and carbohydrates in respiration

Question 13

What are prosthetic groups needed for?

Answer 13

They are required by enzymes to carry out their function so are a type of cofactor

Question 14

How do prosthetic groups bind?

Answer 14

They are permanently and tightly bound to the enzyme

Question 15

What is an example of a prosthetic group?

Answer 15

Carbonic anhydrase is involved in the metabolism of carbon dioxide and it has a zinc ion, forming an important part of its structure

Question 16

What is an apoenzyme?

Answer 16

An enzyme in its inactive form how thy are often made

Question 17

What is a holoenzyme?

Answer 17

An activated enzyme

Question 18

What is an example of enzyme activation?

Answer 18

A protease enzyme is used to activate the inactive form of another enzyme by chopping through bonds in the protein

Question 19

What is the inactive precursor of an enzyme called?

Answer 19

A zymogen or proenzyme

Question 20

How are enzymes activated by temperature or pH?

Answer 20

The surrounding temperature or pH may have to change to activate an an enzyme which changes the tertiary structure

Question 21

What is an example of pH activation?

Answer 21

Pepsinogen is released into the stomach to digest protein in its inactive form and the acid in the stomach activates the proenzyme turning it into pepsin (the active form)

Question 22

What is thrombin?

Answer 22

An enzyme which catalyses the conversion of fibrinogen (factor I), a soluble plasma protein, into a long, sticky thread of insoluble fibrin

Question 23

What do fibrin threads form?

Answer 23

A mesh that traps platelets, blood cells and plasma

Question 24

How do you calculate rate using end point?

Answer 24

You divide the time to get the rate

Question 25

What are the units of rate?

Answer 25

s⁻¹