2.4 Factors Affecting Enzyme Activity

Question 1

Name 4 factors affecting enzyme activity:

Answer 1

• temperature
• PH
• enzyme concentration
• substrate concentration

Question 2

What happens to the rate of reaction when temperature increases?

Answer 2

Rate of reaction increases

Question 3

What does more heat provide the molecules with?

Answer 3

More kinetic energy

Question 4

If the molecules have more KE what happens?

Answer 4

The molecules move faster

Question 5

The faster the molecules (substrate) move what is more likely to occur?

Answer 5

collisions with enzymes, meaning there is more chance of a reaction

Question 6

What does a rise in temperature do to enzyme molecules?

Answer 6

Makes them vibrate more

Question 7

What happens with the vibrations if the temperature goes above a certain level?

Answer 7

The vibrations break some of the bonds that are holding the enzymes shape

Question 8

What happens to the enzyme if bonds holding its shape are broken?

Answer 8

• active site changes shape
• substrate no longer fits
• enzyme is denatured

Question 9

What is optimum temperature?

Answer 9

The temperature at which an enzyme works best (rate of reaction is highest)

Question 10

What is the optimum temperature for most human enzymes?

Answer 10

37°c

Question 11

At what ph do most human enzymes work best at?

Answer 11

PH7

Question 12

What PH does pepsin work best at? Why is this useful?

Answer 12

• PH 2 (acidic)

* useful as it is found in the stomach

Question 13

What happens to the H+ and OH- ions found in acids and alkalis above and below optimum PH?

Answer 13

• they can mess up the ionic and hydrogen bonds holding the enzymes tertiary structure in place

Question 14

What does a change in the enzymes tertiary structure cause?

Answer 14

Change in the shape of the active site

Question 15

What happens if the active site changes shape?

Answer 15

• enzyme and substrate no longer fit

* enzyme is denatured

Question 16

What is more likely to happen the higher the enzyme concentration?

Answer 16

Collisions with substrate and the formation of enzyme-substrate complexes

Question 17

What effect does increasing substrate concentration have on the rate of reaction?

Answer 17

• increased substrate concentration means increased rate of reaction

Question 18

If the amount of substrate is limited what effect does increasing enzyme concentration have? Why?

Answer 18

• No effect

* because there is more than enough enzymes to deal with the available substrate

Question 19

The higher the substrate concentration…?

Answer 19

The faster the rate of reaction

Question 20

Why does increased substrate concentration mean increased rate of reaction?

Answer 20

There are more substrate molecules increasing the chance of collision between enzyme and substrate

Question 21

What happens to the rate of reaction if you add more substrate after the saturation point?

Answer 21

• no effect on the rate of reaction

Question 22

Why is there no effect on the rate of reaction when adding more substrate after the saturation point?

Answer 22

• too many substrate molecules

* all the enzymes active sites are full

Question 23

How can you measure the rate of enzyme controlled reactions?

Answer 23

• speed of appearance of product

* the speed of disappearance of substrate

Question 24

Give an example of an experiment for measuring the speed of product appearance?

Answer 24

• catalase catalysing the break down of hydrogen peroxide to oxygen and water
• collecting the oxygen produced whilst measuring how fast it is given off

Question 25

Give an example of an experiment used to measure the disappearance of substrate?

Answer 25

• amylase catalysing the breakdown of starch to maltose
• detect starch using potassium iodide and iodine solution
• time how long it takes the starch to disappear