Enzymes

Question 1

Role and structure of enzymes

Answer 1

• all reactions require a minimum amount of energy to proceed
• this is known as activation energy

Enzymes are catalysts
- this means they increase rate of reaction
- they lower the activation energy of a reaction without undergoing a permanent change themselves

Question 2

Intracellular enzyme e.g.

Answer 2

Catalase- breaks down hydrogen peroxide

Question 3

Extracellular enzymes e.g.

Answer 3

Amylase- breaks down starch

Trypsin- breaks down protein

Question 4

How is a reaction catalysed

Answer 4

When a substrate binds to the active site of an enzyme- this is known as an enzyme substrate complex
- the shape of the active site is determined by the tertiary structure

Question 5

Lock and key model

Answer 5

Proposes the enzymes active site and substrate has fixed complementary shapes

Question 6

Induced fit model

Answer 6

Induced fit model says that the substrate and active site aren’t initially complementary
When the substrate starts to bind to bind, the active starts to change shape and becomes complementary
This puts stress on the substrate binds, making them easier to break and therefore lowers the activation energy

Question 7

What is the inactive form that enzymes are produced in

Answer 7

Precursors

Question 8

3 types of cofactors

Answer 8

inorganic ions- temporarily bind to the enzyme e.g. chloride ions are cofactors for amylase

coenzymes- temporarily bind to the enzymes e.g. vitamins

prosthetic groups- permanently bind ti the enzyme e.g. zinc ion is permanently bound to carbonic anhydrase

Question 9

Factors affecting enzyme-controlled reactions

Answer 9

Enzyme concentration- increases active sites available, increases chance of enzyme substrate complexes forming

Substrate concentration- increases change of enzyme substrate complexes forming

Competitive inhibitors- complementary to the active site, lowering the probability of enzyme substrate complexes forming . They initially decrease rate of reaction but max. RoR is still reached since competitive inhibitors don’t permanently bind to active site

Non competitive inhibitors- don’t bind to an enzymes active site but to the allosteric site, causing the active site to change shape. When active site and substrate are no longer complementary, this prevents enzyme substrate complexes forming. This decreases RoR as well as max. rate of reaction since increasing substrate conc is no longer effective

Question 10

End product inhibition

Answer 10

The final product of a pathway inhibits the enzymes involves

Question 11

Temperature coefficient

Answer 11

Q₁₀ = R₂
R₁