2.4 enzymes

Question 1

Definition of an intracellular enzyme

Answer 1

they are produced and function inside the cell

Question 2

Definition of an extracellular enzyme

Answer 2

secreted by cells and catalyse reactions outside of the cell

Question 3

Induced fit hypothesis

Answer 3

• the enzyme and the active site change shape slightly as the substrate molecules begins to enter the enzyme
• these changes are known as conformational changes
• they ensure an ideal binding arrangement is achieved
• this maximises the ability of it to catalyse reactions

Question 4

Why at high levels of pH do enzymes become denatured?

Answer 4

• hydrogen and ionic bonds hold together the tertiary structure of the protein together
• below or above optimum pH an excess of H+ ions or OH- ions can build up causing the bonds to break
• the broken bonds change the shape of the active site so eventually enzyme substrate complex’s can no longer form

Question 5

Why are buffer solutions used in experiments

Answer 5

• they maintain a specific pH even if the reaction would otherwise change the pH

Question 6

What is the temperature coefficient

Answer 6

the ratio between the rates of that reaction at two different temperatures

Question 7

Equation for the temperature coefficient

Answer 7

Q10= rate of reaction at x+10 / rate of reaction at x

Question 8

What is a competitive inhibitor

Answer 8

they have a similar shape to that of the substrate molecule

Question 9

What is a non-competitive inhibitor

Answer 9

bind to the allosteric site which alters the shape of the active site preventing the substrate from binding to it

Question 10

How to reverse increased competitive inhibitor concentration

Answer 10

increasing the substrate concentration as that means they are more likely to collide with enzymes

Question 11

How to reverse increased non-competitive inhibitor concentration

Answer 11

increasing substrate concentration will NOT do anything as the active site has already changed shape

Question 12

Process of end-product inhibition

Answer 12

1. as the enzymes convert the substrate into product, the process is slowed down as the end-product of the reaction chain binds to an allosteric site
2. the end product can then detach and be used elsewhere allowing the active site to reform
3. this means as the product falls the enzyme catalyses the reaction once again in a CONSTANT FEEDBACK LOOP

Question 13

How to inhibitors form irreversible reactions

Answer 13

form covalent bonds with the enzymes

Question 14

Why are irreversible inhibitors dangerous

Answer 14

their biological reaction the enzyme is catalysing will be completely stopped

Question 15

Definition of cofactor

Answer 15

inorganic ions that an enzyme needs in order to function
minerals
non-protein

Question 16

Role of a cofactor

Answer 16

stabilise the structure of the enzyme or they may take part in the reaction at the active site

Question 17

Definition of coenzyme

Answer 17

large organic cofactors
vitamins

Question 18

Role of a coenzyme

Answer 18

carry electrons or chemical groups between enzymes, aiding catalysis
found at/in the active site (can be permanently bound to the active site)

Question 19

Definiton of a prosthetic group

Answer 19

permanent part of the enzyme structure to that they assist

Question 20

Role of a prosthetic group

Answer 20

help to form the final 3D shape of the enzyme