Enzyme Action

Question 1

What are enzymes?

Answer 1

Tertiary structure proteins which catalyse reactions.

Question 2

Why is the active site specific and unique in shape?

Answer 2

Due to the specific folding and bonding in the tertiary structure of the protein.

Question 3

What part of the enzyme attaches to the substrate to catalyse a reaction?

Answer 3

The active site.

Question 4

What do substrates have to be to attach to an enzyme?

Answer 4

Complementary in shape with the enzymes active site.

Question 5

What do enzymes and substrates attach to form?

Answer 5

Enzyme-substrate complexes.

Question 6

What is the activation energy?

Answer 6

The amount of energy a reaction requires to occur.

Question 7

What do enzymes do when they attach to substrates?

Answer 7

Lower the activation energy needed and therefore speed up the reaction.

Question 8

What are the two enzyme and substrate models?

Answer 8

The lock and key model and the induced fit model.

Question 9

What does the lock and key model suggest?

Answer 9

That the enzyme is a lock and the substrate is a key that fits into it due to their complementary shape. And that the enzyme active site is a fixed shape.

Question 10

How does the substrate attach to the enzyme in the lock and key model?

Answer 10

Due to random collisions.

Question 11

What happens after an enzyme-substrate complex has formed in the lock and key model?

Answer 11

It causes the substrate to distort shape, lowering the activation energy. And the products are then released.

Question 12

What happens to the enzyme after the products are released?

Answer 12

It is reused.

Question 13

What does the induced fit model suggest?

Answer 13

The enzyme is like a glove and the substrate a hand; they are not exactly complementary in shape but the enzyme moulds around the substrate to become complementary.

Question 14

What does the enzymes active site do to fit around the substrate in the induced fit model?

Answer 14

Slightly changes shape or is induced.

Question 15

What happens due to the enzyme moulding around in the induced fit model?

Answer 15

It puts strain on the bonds making them easier to break and therefore lower the activation energy.

Question 16

What happens to the enzyme after the products are removed in the induced fit model?

Answer 16

The enzymes active site returns to it’s original shape.

Question 17

What model for an enzymes function is accepted?

Answer 17

The induced fit model.

Question 18

What are the factors that affect enzyme controlled reactions?

Answer 18

Temperature, pH, substrate concentration, enzyme concentration, and inhibitors.

Question 19

What does it mean if the temperature is too low for an enzyme-controlled reaction?

Answer 19

There is not enough kinetic energy for successful collisions between the enzyme active site and the substrate, which results in fewer enzyme-substrate complexes.

Question 20

What does it mean if the temperature is too high for an enzyme-controlled reaction?

Answer 20

The enzyme denatures and enzyme-substrate complexes cannot form.

Question 21

Why does high temperature denature an enzyme?

Answer 21

It causes the bonds in the enzyme’s active site to break and therefore change shape.

Question 22

What happens if the pH is too high or low in an enzyme-controlled reaction?

Answer 22

It will interfere with the charges of the amino acids in the active site and will cause the bonds holding the tertiary structure in place to break, denaturing the enzyme and forming fewer enzyme-substrate complexes.

Question 23

What happens if there is insufficient substrate in an enzyme-controlled reaction?

Answer 23

The reaction will be slower as there will be fewer collisions between the enzyme and substrate.

Question 24

What happens if there is insufficient enzymes in an enzyme-controlled reaction?

Answer 24

The enzyme active sites will become saturated with substrate and unable to work any faster.

Question 25

What do competitive inhibitors do?

Answer 25

Prevent the substrate from binding and the reaction from occurring.

Question 26

How can competitive inhibitors prevent a reaction from occurring?

Answer 26

They are the same shape as the substrate, so bind with the active site instead of the substrate.

Question 27

What do competitive inhibitors form when they bind with the enzyme active site?

Answer 27

Enzyme-inhibitor complexes.

Question 28

How could you out-compete a competitive inhibitor?

Answer 28

By adding more substrate.

Question 29

What do non-competitive inhibitors do?

Answer 29

Bind to the enzyme away from the active site (the allosteric site).

Question 30

What does a non-competitive inhibitor cause when it binds to the allosteric site on the enzyme?

Answer 30

The active site’s tertiary structure changes shape so the substrate can no longer bind and form an enzyme-substrate complex.

Question 31

What is a disadvantage with non-competitive inhibitors?

Answer 31

Adding more substrate won’t knock out the inhibitor like competitive inhibitors.