04. Enzymes

Question 1

What is an enzyme?

Answer 1

a protein biological catalyst, that speeds up chemical reactions by lowering the activation energy of reactions.

Question 2

Draw a 3-part enzyme diagram.

Answer 2

Question 3

Explain what determines the structure of the active site.

Answer 3

Because the enzyme (protein) is made from a sequence of amino acids then the R groups from these determine the bonds that will form. Therefore leading to the overall 3D structure, including the active site.

Question 4

Define metabolism

Answer 4

The sum total of all chemical reactions occurring in an organism

Question 5

What does a synthesis reaction mean?

Answer 5

Two substrates combine to form one product

Question 6

What does a decomposition reaction mean?

Answer 6

One substrate breaks down to form two products

Question 7

What factors affect the rate of enzyme reactions?

Answer 7

Temperature
pH
Enzyme concentration
Substrate concentration
Competitive inhibitors
Non-competitive inhibitors

Question 8

Draw an enzyme Rate of reaction vs temperature graph

Answer 8

Question 9

Explain why the enzyme controlled reaction is low at a low temperature

Answer 9

Because the enzymes are inactive
Then there is less kinetic energy and it is less likely to have successful collisions between enzymes and substrate
Therefore less enzyme-substrate complexes will form, less products will form and there is a lower rate of reaction

Question 10

Define optimum temperature

Answer 10

Temperature where the enzyme works best and there is the most enzyme substrate complexes forming.

Question 11

Explain why the enzyme controlled reaction is low at a high temperature

Answer 11

Because there is too much kinetic energy the enzyme’s denature
Then the 3D structure of the active site has changed shape so it is no longer specific and complementary to the substrate
Therefore less enzyme-substrate complexes will form and there will be less products and a lower rate of reaction.

Question 12

Draw an enzyme Rate of reaction reaction vs pH graph

Answer 12

Question 13

Explain why the enzyme controlled reaction is low at a low pH

Answer 13

Because the pH is too low the enzyme’s denature
Then the 3D structure of the active site has changed shape so it is no longer specific and complementary to the substrate.
Therefore less enzyme-substrate complexes will form and there will be less products formed and a lower rate of reaction.

Question 14

Explain why the enzyme controlled reaction is low at a high pH

Answer 14

Because the pH is too high the enzyme’s denature
Then the 3D structure of the active site has changed shape so it is no longer specific and complementary to the substrate.
Therefore less enzyme-substrate complexes will form and there is less products and a lower rate of reaction.

Question 15

Draw an enzyme rate of reaction vs enzyme concentration (assuming unlimited substrate concentration)

Answer 15

Question 16

Draw an enzyme rate of reaction vs substrate concentration graph

Answer 16

Question 17

Explain how a competitive inhibitor lowers the rate of an enzyme controlled reation

Answer 17

Because competitive inhibitors are specific and complimentary to the active site of the enzyme, then they bind to the active site instead of the substrate. Therefore less enzyme-substrate complexes form, less products and the rate of reaction is lower.

Question 18

Explain how a non-competitive inhibitor lowers the rate of an enzyme controlled reaction.

Answer 18

Because non-competitive inhibitors bind to the allosteric site (not the active site), then the 3D structure of the active site changes shape so that it is no longer specific and complimentary to the substrate. Therefore less enzyme-substrate complexes form, less products and the rate of reaction is lower.

Question 19

Draw a 3-part enzyme diagram showing competitive inhibition

Answer 19

Remember to always draw the normal 3-part enzyme diagram first.

Question 20

Draw a 3-part enzyme diagram showing non-competitive inhibition

Answer 20

Question 21

How can the rate of reaction be increased in the presence of a competitive inhibitor?

Answer 21

Increase substrate concentration

Question 22

What is an enzyme-substrate complex?

Answer 22

When the enzyme and substrate have successfully collided and bound together

Question 23

What factors cause an enzyme to denature?

Answer 23

High temperatures (above the optimum), high or low pH (above or below the optimum)

Question 24

Why does the graph plateau in an enzyme rate of reaction vs substrate concentration graph?

Answer 24

Because all enzyme active sites are occupied with substrate
Then the maximum number of enzyme substrate complexes are already forming each second
Therefore the reaction rate plateaus and cannot increase regardless of an increase in substrate.