Factors affecting enzyme action

Question 1

How can we measure the progress of an enzyme-catalyzed reaction?

Answer 1

• The formation of the products e.g. volume of O2 produced when enzyme catalase acts on hydrogen peroxide.
• The disappearance of the substrate e.g. the reduction of starch when acted upon by amylase.

Question 2

Describe the reaction between hydrogen peroxide and oxygen on a graph. (increasing from 0-10cm3)

Answer 2

• At first, there’s a lot of substrates- Hydrogen peroxide but no product - Oxygen.
• So it’s easy for the substrate to come in contact with an empty active site on an enzyme molecule.
• When the active sites are filled with substrate, it’s broken down into its products.
• As the substrates are broken down, the amount decreases but the amount of products increase.
• As the reaction proceeds, more and more products are produced and less of the substrate.
• It would become more difficult for the substrate to come into contact with the enzyme molecule because there are fewer of them and the products might get in the way.
• Therefore it would take longer for the remaining substrates to be broken down so the RoR decreases and graph would level off.
• The graph will flatten out because all of the substrates has been used up and no new products can be formed.

Question 3

What does PH mean?

Answer 3

PH is the measure of the concentration of H+ ions.

PH1 has the most H+ ions.

Question 4

How can we measure the change in the rate of reaction on a curve?

Answer 4

Tangent can be drawn over the given time

the difference in Y/ the difference in X.

Question 5

How does temperature affect the RoR of enzyme action?

Answer 5

• A rise in temperature increases the kinetic energy.
• So the molecules move around more rapidly and collide with each other more frequently- successful collision.
• More enzyme-substrate complexes are formed therefore the RoR increases.

Question 6

What is denaturation?

Answer 6

At a high temperature, the enzyme is denatured, where their active sites are changed permanently causing them unable to function.

Question 7

What would a high temperature in our body do?

Answer 7

• Higher body temperature would increase the metabolic rate slightly but additional energy e.g. from food is needed to maintain the high temperature.
• Other proteins, apart from enzymes might be denatured at a higher temperature.
• Any further rise in temperature e.g. illness might cause the enzyme to denature.

Question 8

What does optimum pH mean?

Answer 8

The PH which the enzyme works fastest.

Question 9

How can you calculate the pH of a solution?

Answer 9

pH = -log10 (H+) e.g. (H+) of 1x10-9 has a pH of 9.

Question 10

How does pH affect an enzyme reaction?

Answer 10

• A change in pH changes alters the charges on the amino acids which makes up the active site of the enzyme and depending on how significant the change in pH is, its hydrogen bonds within the tertiary structure causing it to break and the active site, therefore, would change shape.
• As a result, the substrate can no longer become attached to the active site so no E-S complex can be formed because they are no longer complementary so the RoR slows down.

Question 11

How does enzyme concentration affect the RoR?

Answer 11

• As long as there’s an excess amount of substrate, an increase in enzyme concentration would lead to a proportionate increase of RoR.
• On a graph, there’ll be a few enzyme molecules at the start so it’s difficult for the excess substrate to find a free active site. Therefore the RoR at the start is half of the maximum RoR.
• If we increase the concentration of the enzymes, there’ll be enough active site for all of the substrates to react with therefore the RoR increases.
• However, if we continue to increase the number of enzymes, the substrate will become a limiting factor because there won’t be enough substrate to into every enzyme’s active site therefore even with an increase of enzyme concentration, there’ll be no effect on the RoR so the graph would level off.

Question 12

How does substrate concentration affect the RoR?

Answer 12

• At the very start, there’ll be a few substrate molecules to occupy the active sites so RoR is half of its maximum possibility because the enzyme molecules have only a limited number of substrate molecules to collide with.
• When more substrate is added, the active site gradually becomes filled until all becomes occupied so the RoR increases to its maximum possibility.
• After this, further addition of substrates won’t have an effect upon the reaction because there’s no free active sites for them to react with therefore the graph would level off.