SBI 4U
Date:
Enzyme Investigation
Objectives:
 To measure the effects of changes in temperature and pH on the reaction rates of an enzyme catalyzed reaction
in a controlled experiment.
Background:
What would happen to cells if they made a poisonous chemical? One might think that they would die. In fact, cells are
always making poisonous chemicals. They do not die because cells use enzymes to break down these poisonous
chemicals into harmless substances. Enzymes are proteins that speed up the rate of reactions that would otherwise
happen more slowly. The enzyme is not altered by the reaction. Hundreds of different enzymes exist in each cell.
Each of these enzymes is responsible for one particular reaction that occurs in the cell. In this lab, you will study an
enzyme that is found in the cells of many living tissues. The name of the enzyme is catalase, which speeds up a reaction
which breaks down hydrogen peroxide, a toxic chemical, into two harmless substances--water and oxygen.
The reaction is as follows: 2H2O2 ----> 2H2O + O2
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a by-product of many normal cellular
reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die. In this lab, you will
study the catalase found in liver cells. You will be using chicken or beef liver. It might seem strange to use dead cells to
study the function of enzymes. This is possible because when a cell dies, the enzymes remain intact and active for
several weeks, as long as the tissue is kept refrigerated.
Hypotheses: Make a hypothesis about how you think temperature and pH will affect the rate at which the enzyme
peroxidase breaks down hydrogen peroxide. Consider both high and low temperatures and pH. Provide reasoning for
each hypothesis. (2 marks)
Procedure: Examine the list of materials provided below. With your partner, create a detailed procedure to test your
hypotheses. Your experimental design should include controls and test one variable at a time. Determine your
independent and dependent variables. Also consider how you will measure the amount of oxygen produced, and if you
will be collecting qualitative or quantitative data. (5 marks)
Materials:
1 molar HCl solution
1 molar NaOH solution
test tubes
pipette
hot plates
3% hydrogen peroxide
solution
scalpel
scissors and forceps
(tweezers)
thermometers
stirring rod
pH paper
liver
test tube holders
Observations:
Create data tables to record all observations. (4 marks)
any other glassware or
material you may
require
Analysis:
Create one graph showing the relationship between temperature and amount of oxygen produced, and one graph
showing the relationship between pH and oxygen produced. (4 marks)
Discussion:
Answer the following questions in your discussion:
1. What was the control solution in your study? Explain why this is a control. (2 marks)
2. Explain how varying the pH influenced the rate of the catalase reactions. Make specific reference to enzyme structure
in your discussion. (2 marks)
3. Explain how varying the temperature influenced the rate of the catalase reactions. Make specific reference to
enzyme structure in your discussion. ( 2 marks)
4. In class we learned that some enzymes in living systems function optimally at specific temperatures and pH values.
Based on your findings, what are the optimal conditions for beef liver catalase? (2 marks)
5. If an enzyme from a thermophilic bacteria were used in place of beef liver catalase, how would expect your results to
vary? (1 mark)
Error Analysis:
Discuss two errors that could have occurred in this lab and ways to mitigate each. (4 marks)
Purpose:
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Procedure:
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Observations:
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Analysis:
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Conclusion:
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Discussion:
Question 1
Question 2
Question 3
Question 4
Question 5
T/I
/33
C
/10
5