Factors affecting the rate of enzyme activity
Under normal conditions, hydrogen
peroxide will slowly but spontaneously
decompose into water and a gas.
Manganese dioxide is a chemical
catalyst that can speed up this reaction
so that it happens in the matter of
seconds.
Hydrogen peroxide is a harmful
byproduct of metabolism. To prevent
damage to cells and tissues, hydrogen
peroxide must be quickly converted into
other less harmful substances. Catalase,
a biological catalyst that is present in the
cells of most living organisms, carries out
this process. This protein based enzyme is
easily obtained from beef or chicken liver,
potatoes and yeast.
In this experiment, you will investigate how
different environmental conditions affect
the enzymatic activity of catalase.
Materials
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3% hydrogen peroxide (H2O2)
manganese dioxide (MnO2)
fresh liver
potato
fine sand
0.1 M NaOH
0.1 M HCl
distilled water
water (boiling)
ice
Apparatus
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Hot plate
Test tubes
Test tube rack
Stirring rods
Test tube stoppers
600 mL beakers
matches
tea light candles
wooden splint
thermometers
stopwatches
test tube holders
scoopulas
beaker tongs
10 mL graduated cylinders
Knife
cutting board
goggles
electronic balance
Procedure
Part A – Enzyme & substrate concentration
1. Take 4 test tubes and place 0.1 g of sand into one, 0.1 g of
manganese dioxide into another, a small piece of potato
into the third and a small piece of liver into the last tube.
2. Add 2 mL of hydrogen peroxide to each test tube.
3. Time the reaction as soon as the hydrogen peroxide is
added. Stop timing when the reaction is over. Record the
rates of reaction and changes observed during the
reaction.
4. Perform a glowing splint test on all the test tubes to
determine the type of gas produced.
5. Use the test tube containing the liver from the above steps
and add another piece of liver of approximately the same
size to it.
6. Record the reaction time and changes observed during
the reaction.
7. Take the same liver test tube and add another 2 mL of
hydrogen peroxide to it.
8. Record the reaction time and changes observed during
the reaction.
Part B – Temperature
9. Take 3 test tubes and place a small piece of liver into each
of them.
10. Add 1 mL of distilled water into each.
11. Place one test tube into a boiling water bath for 5 minutes.
12. Place one test tube into a water bath with a temperature
of approximately 37C for 5 minutes.
13. Place one test tube into an ice water bath for 5 minutes.
14. Remove all 3 test tubes and to each add 2 mL of hydrogen
peroxide.
15. Record the reaction time and changes observed during
the reaction.
Part C – pH
16. Cut 3 pieces of liver so that they are approximately equal
in size and place each piece into a separate test tube.
17. To one test tube also add 1 mL of NaOH, to another add 1
mL of HCl and to the last one add 1 mL of distilled water.
18. Add 2 mL of hydrogen peroxide to each test tube.
19. Record the reaction time and changes observed during
the reaction.
Clean up & Disposal
 Solid pieces (e.g. liver, potato) can go into the regular
waste.
 Liquid waste should be poured into the chemical waste
container provided.
 All glassware should be washed and left to dry upside
down.
 Marks can be deducted for improper cleanup.
Pre-lab [10 marks, inquiry]
These pre-lab questions are to be handed in to the instructor before performing the experiment.
1. Predict the effect of the following changes on catalase activity and explain your rationale for each. [8]
a. enzyme concentration
b. substrate concentration
c. temperature
d. pH
2. Explain the purpose of adding sand to tube 1. Why is this test necessary and how is it useful? [2]
Write Up [45 marks]
Even though this write-up is not a complete lab report, all aspects that are included should be treated as a
formal report. Written Individually.
Title [1 mark, Communication]
Select a concise and appropriate title for this lab. A reader should read the title and have a good idea of
what the lab was about. The title should NOT be the same as the title of this handout.
Abstract [5 marks, Communication]
Although placed first in the write-up, the abstract will be the last thing that you write. It is a short summary of
the lab (~100 words) that explains the purpose and summarizes the key findings.
Observation table [10 marks, communication]:
 Completion and accuracy [5]
 Thorough observations [5]
Conclusion [14 marks, application]:
Answer the following using multiple paragraphs rather than in question-answer form
 Does the enzyme in liver and potato catalyze the same reaction as manganese dioxide? Support your
answer with evidence from the lab. Refer specifically to observations recorded on table 1. [2]
 Include in your discussion the chemical equation for the decomposition of hydrogen peroxide.
 Which substance had more catalase: liver or potato? Explain how you made this conclusion. [2]
 Explain the effect observed when more liver was added to tube 4. Support your answer with evidence from
the lab. Use terms like substrate, enzyme, concentration etc. [2]
 Explain the effect observed when more hydrogen peroxide was added to tube 4. Support your answer with
evidence from the lab. Use appropriate terminology. [2]
 Compare the effect of the different temperatures on enzyme activity. Give an explanation for the
observation. [2]
 Compare the effect of the different pH on enzyme activity. Give an explanation for the observation. [2]
 State the ideal conditions for a high reaction rate with catalase. [2]
Sources of error [10 marks, inquiry]
Often when performing a lab experiment, there are inconsistencies in the results / data. These inconsistencies
can often be accounted for by some detail in the procedure and is known as a source of error.
 Describe 3 such sources of errors that could have occurred in this lab and how it would affect the results.
Note: answers that relate to mistakes that could have been corrected are not valid.
 Provide 2 detailed suggestions on how to improve the accuracy of the lab.
Language [5 marks; Communication]
Proper sentence and paragraph structure should be used in this report. It should be written in a past, passive
voice; therefore no personal pronouns should be used. Ideas should flow logically and are prefaced by linking
words. The writing should be clear and concise and there should be no grammar or spelling errors. You should
have a peer edit your report. The editor does not need a science background.
Table 1 - Changes observed on the rate of reaction when different
environmental stresses were performed on the enzyme catalase.
Part
Tube
Contents
1
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0.1 g sand
2 mL H2O2
Negative
Control
2
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0.1 g MnO2
2 mL H2O2
Positive
control
3
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Small piece of potato
2 mL H2O2
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Small piece of liver
2 mL H2O2
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Add another small piece
of liver to tube 4
A
4
5
B
6
7
8
C
Factor being
tested
9
10
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Add another 2 mL H2O2
to tube 4
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Small piece of liver
1 mL dH2O
boiling water for 5 min
2 mL H2O2
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Small piece of liver
1 mL dH2O
37oC water bath for 5 min
2 mL H2O2
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Small piece of liver
1 mL dH2O
ice water bath for 5 min
2 mL H2O2
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Small piece of liver
1 mL NaOH
2 mL H2O2
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Small piece of liver
1 mL HCl
2 mL H2O2
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Small piece of liver
1 mL dH2O
2 mL H2O2
Enzyme
concentration
Substrate
concentration
temperature
pH
Reaction time
Changes observed