Many proteins are enzymes

Question 1

What protein structure do enzymes have and their function?

Answer 1

Enzymes are tertiary structure proteins which catalyse reactions

Question 2

Describe the active site.

Answer 2

It is specific and unique in shape due to the specific folding and bonding in the tertiary structure of a protein. This means that enzymes can only attach to substrates that are complementary in shape forming an enzyme-substrate complex.

Question 3

What are the 2 models of enzyme action?

Answer 3

Lock and key, Induced fit model.

Question 4

What can enzymes do when they attach to the substrate in terms of the reaction?

Answer 4

They lower the activation energy needed for the reaction to occur and therefore speed up the reaction.

Question 5

Explain the lock and key model.

Answer 5

• The enzymes active site is a fixed shape
• Due to random collisions, the substrate can collide and attach with the active site to form an enzyme-substrate complex
• The substrate will slightly distort in shape causing the activation energy to become lower.
• The products are then released and the enzyme active site is empty and ready to be reused.

Question 6

Explain the induced fit model.

Answer 6

• The enzymes active site slightly changes shape to mould around and become complementary to the substrate
• This causes the enzyme-substrate complex to occur
• Due to the enzyme moulding around the substrate, the bonds around the substrate weaken which lowers the activation energy.
• The products are then released and the active site returns to its original shape

Question 7

State all the factors that affect the rate of an enzyme controlled reaction.

Answer 7

• Temperature
• pH
• Substrate concentration
• Enzyme concentration
• Inhibitors

Question 8

How does temperature affect the rate of an enzyme controlled reaction?

Answer 8

• If the temperature is too low then there will not be enough kinetic energy for successful collisions between the enzyme and the substrate.
• If the temperature is too high or beyond the optimal temperature, it will cause the enzyme to denature and the active site to change shape which means enzyme-substrate complexes cannot form.

Question 9

How does pH affect the rate of an enzyme controlled reaction?

Answer 9

• Too high or too low of a pH will interfere with the charges in the amino acids in the active site. This can break the bonds holding the tertiary structure which therefore changes the shape of the active site. This causes the enzyme to denature so fewer enzyme-substrate complexes can be formed.

Question 10

How does substrate concentration affect the rate of an enzyme controlled reaction?

Answer 10

• If the substrate concentration is low then the rate of reaction will be slower because there will be fewer substrates to collide with the enzymes and form enzyme-substrate complexes.
• At one point when you increase the substrate concentration, the rate of reaction stays constant because the enzymes active sites become saturated, every single active site is already in use.

Question 11

How does enzyme concentration affect the rate of an enzyme controlled reaction?

Answer 11

• If the enzyme concentration is low then the rate of reaction will be slower because the enzymes active site will become saturated with the substrate and unable to work any faster.
• At one point when you increase the enzyme concentration, the rate of reaction stays constant because there are empty active sites due to far more enzymes than substrates, there are not enough substrates to collide with the empty active sites.

Question 12

What is an inhibitor and what are the two types?

Answer 12

A molecule that binds onto the enzyme and prevents the enzyme from functioning.
- Competitive and non-competitive inhibitor

Question 13

What is a competitive inhibitor and what does it do?

Answer 13

A competitive inhibitor is similar in shape to the substrate and is complementary in shape to the active site and binds to the active site to prevent the substrate from binding and the reaction from occurring.

Question 14

How can you flood out the competitive inhibitor?

Answer 14

By adding more substrate, it will flood out the competitive inhibitor and knock them out of the active site

Question 15

What do non-competitive inhibitors do?

Answer 15

They bind to the enzymes away from the active site which causes the active site to change shape which means the substrate can no longer bind regardless of how much substrate it added.