Enzymes 1

Question 1

How do enzymes increase the rate of reaction?

Answer 1

Enzymes lower the activation energy for a reaction.

Question 2

Explain how the formation of the enzyme-substrate complex causes a high rate of reaction

Answer 2

The substrate fits into the complimentary active site and makes temporary bonds. There is a slight change in the shape of the active site, placing strain on the bonds in the substrate. This lowers the activation energy for the reaction and increases the rate of reaction.

Question 3

Why can a small quantity of enzyme be effective?

Answer 3

Enzymes do not get used up in the reaction, and can be reused.

Question 4

Why can changing an amino acid in the active site prevent the enzyme from functioning?

Answer 4

The sequence of amino acid changes the 3-D tertiary of the active site so that it no longer binds to the substrate.

Question 5

Why do enzymes only work with one substrate?

Answer 5

The actives sites are different specific shapes, the 3-D tertiary structure of the active site is complimentary to only one substrate, so different enzyme-substrate complexes are formed.

Question 6

Describe and explain how non-competitive enzyme inhibitors affect the rate of enzyme controlled reaction.

Answer 6

The inhibitor binds to a site other than the active site, this changes the shape of the active site, preventing the formation of enzyme-substrate complexes, lowering the rate of reaction. This cannot be overcome by adding more substrate.

Question 7

Describe and explain how competitive enzyme inhibitors affect the rate of enzyme controlled reaction.

Answer 7

The inhibitor is a similar shape to the substrate (complimentary to the active site), it binds to the active site of the enzyme preventing enzyme-substrate complexes forming. Adding more substrate can overcome the inhibition.

Question 8

Explain how enzymes allow reactions to take place at body temperature.

Answer 8

Enzymes are catalysts they lower the activation energy for a reaction by forming enzyme-substrate complexes.

Question 9

Explain why pH affects enzyme function

Answer 9

Enzymes have an optimum pH where they work best. Away from the optimum pH the enzymes H-bonds and ionic bonds are changed, changing the shape of the active site, preventing enzyme-substrate complexes from forming. The enzyme is denatured.

Question 10

Describe the biochemical test for an enzyme

Answer 10

Add Biurets reagent to the test solution. A positive result is from blue to purple.