2: Factors Affecting Enzyme Activity

Question 1

Name some conditions which affect the rate at which enzymes catalyse chemical reactions.

Answer 1

temperature, pH, AND substrate concentrations

Question 2

Sketch a graph showing the effect of temperature on enzyme activity. Explain why it has this shape. (p27)

Answer 2

-

Question 3

Sketch a graph showing the effect of substrate concentration on enzyme activity. Explain why it has this shape. (p27)

Answer 3

-

Question 4

Sketch a graph showing the effect of pH on enzyme activity. Explain why it has this shape. (p27)

Answer 4

-

Question 5

How could we investigate the effect of temperature, pH or substrate concentration on enzymes?

Answer 5

with an experiment

Question 6

Explain what you must consider when designing an experiment that will give reliable results.

Answer 6

1. independent variable (IV)
2. dependent variable (DV)
3. control variables

Question 7

Explain what you must consider when deciding on your independent variable (IV) in an experiment.

Answer 7

• IV: variable that affects rate of enzyme activity
• just one independent variable
• set the levels - levels need a wide enough range to show all the trends
• method should ensure that each level of the variable is maintained as accurately as possible

Question 8

Explain what you must consider when deciding on your dependent variable (DV) in an experiment.

Answer 8

• DV: measurement you take to asses rate of enzyme activity
• quantitative; S.I units; as accurate as possible
• experiment should be repeated so there are replicate results so that results can be compared to evaluate if they are reliable

Question 9

Explain what you must consider when deciding on your control variable in an experiment.

Answer 9

• other factors that could affect enzyme activity

- must be kept constant so they do not cause differences in results of experiment

Question 10

Give an example of an independent variable in an experiment investigating factors affecting enzymes.

Answer 10

pH from 1 to 14, going up stepwise e.g. 1,2,3,…

think back to ‘things you need to consider when choosing IV’ if you’re wondering why all this info is included

Question 11

Give an example of an dependent variable in an experiment investigating factors affecting enzymes.

Answer 11

• how long it takes for substrate to be used up measured in seconds (to the nearest second)
• quantity of product formed after a certain time

Question 12

Give an example of a control variable in an experiment investigating factors affecting enzymes

Answer 12

if pH is independent variable, temperature would be control variable and must be kept at a suitable temperature using a water bath