Enzymes

Question 1

What is an enzyme?

Answer 1

An enzyme is a globular protein which catalyses the rate of a reaction, with a specific tertiary structure

Question 2

What is an enzyme substrate complex?

Answer 2

Enzymes have an active site with a specific tertiary structure that becomes complementary to specific substrates

Question 3

Describe how the induced fit model works [5 steps]

Answer 3

1. Enzymes have an active site with a specific tertiary structure
2. Before the reaction, the active site isn’t complementary to the substrate
3. Due to induced fit, as the substrate approaches, the active site changes shape and becomes complementary
4. An enzyme-substrate complex forms
5. This stresses the bonds in the substrate (lowering the activation energy) and leads to a reaction

Question 4

What is the lock and key model?

Answer 4

The shape of the active site does not change when the substrate binds to it

Question 5

What is activation energy?

Answer 5

The minimum amount of energy needed for a reaction to occur

Question 6

How do enzymes lower activation energy in anabolic reactions?

Answer 6

Since substrates need to be joined together, the repulsion would be reduced to force them to bond together

Question 7

How do enzymes lower activation energy in catabolic reactions?

Answer 7

Since the substrate needs to have its bonds broken, the active site strains the bonds between the molecule to break them

Question 8

What is the link between concentration and rate of reaction?

Answer 8

The higher the substrate concentration, the faster the reaction. More substrate means more reactions. If the enzyme is the limiting factor, it’s because the enzymes would have been saturated

Question 9

How does temperature increase rate?

Answer 9

Enzyme and substrate both have more kinetic energy –> move faster –> more successful collisions –> more ES complexes –> faster rate

Question 10

How do extremely high temperatures denature enzymes?

Answer 10

Enzymes vibrate so much that H-H bonds break –> changes enzyme’s tertiary structure –> shape denatures as it’s no longer complementary

Question 11

How do competitive inhibitors work?

Answer 11

Similar tertiary structure as substrates, they compete with them to bind to the active site. More inhibitors decreases the probability at which substrates can bind to the active site

Question 12

How do non- competitive inhibitors work?

Answer 12

They bind to another part of the enzyme, affecting the rate. This affects the shape of the active site making it no longer complementary

Question 13

2 ways incorrect pH could denature enzymes

Answer 13

1. the H2 ions could bond to the amino acids on the active site and change its charge
2. they could disrupt the H2 and ionic bonds, affecting the tertiary structure