SBI4U
Lab: Factors Influencing Enzyme Activity
Introduction
What would happen to your cells if they made a poisonous chemical? You might think that they
would die. In fact, your cells are always making poisonous chemicals. They do not die because
your 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. You have hundreds of different enzymes in each
of your cells.
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 it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2
harmless substances--water and oxygen.
Hydrogen peroxide
H2O2
catalase
water + oxygen
catalase
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 potato cells.
Lab Checklist
Pre-Lab:
Before we begin the lab you MUST have completed and shown Ms. Taman:
o Hypothesis (pg. 2)
o Materials (pg. 2)
o Procedure for Part B- Effect of Temperature (pg. 3)
o Observation Tables for Part A&B (pg. 4)
Lab Analysis: Due Oct. 26
By this date you must complete and hand-in:
o All pre-lab material listed above
o Graphs for Part A and Part B (on graphing paper)
o Conclusion (on separate lined paper)
o Discussion Questions (on separate lined paper)
Reminders:
 While you are working with partners for the lab you will be marked individually. All work
submitted should be in your own words and original
 Safety is important! While completing the lab you will be required to wear goggles and
follow all laboratory safety procedures!
1
Purpose:
Hypothesis:
Part A:
Part B:
Materials: (Fill in the amounts needed for the whole lab for your group)
Material
3% Hydrogen Peroxide
Potato Extract
10 mL graduated cylinder
50 mL graduated cylinder
Large Beakers
Dropper
Thermometer
Ice
Electric Kettle
Hot Plate
Test tubes
Goggles
Stop Watch
Amount
150 mL
2
2
1
1
Procedure
Part A – Effect of Enzyme Concentration
CAUTION:
1.
2.
3.
4.
5.
6.
Hydrogen peroxide is corrosive. Prevent contact with the eyes and skin. Wear safety goggles
for this lab exercise.
Get 2 small beakers and 2 micropipettes, label them as 3% H2O2 and potato extract.
Measure 8.0 mL of 3% H2O2 into a 10 mL graduated cylinder using the dropper.
Measure 1.0 mL of the potato extract into another 10 mL graduated cylinder using the dropper.
Combine the H2O2 and potato extract into a 50 mL graduated cylinder.
Record the starting volume of hydrogen peroxide and potato extract.
Record the maximum volume (in mL) of the foam produced after 2 minutes.
Maximum volume
of foam and extract
Starting volume of
H2O2 + potato extract
7.
Volume of foam in mL
Note: Do not pick up or
shake your graduated
cylinder once the
reaction has started!!!
Repeat steps 2, 3, 4 and 5 nine times using first 2 mL of potato extract and then 3 mL, 4 mL, etc. up
to 10 mL.
2
Part B: Effect of Temperature
Design a procedure in the space below to determine the effect of temperature on the rate of
catalase activity. You can use any of the supplies listed in the material section above. Be as
specific as possible in your procedure!
3
Observations:
Part A – Effect of Enzyme Concentration
In the space below create a table for your results. Be sure to include: Volume of H2O2 (ml),
volume of potato extract (ml), starting volume of foam + extract (ml), final volume of foam +
extract (ml), volume of foam (ml).
Plot a graph of rate of reaction (final foam volume) vs. enzyme concentration (volume of extract) on
the attached graph paper.
Plot a graph of rate of reaction (final foam volume) vs. enzyme concentration (volume of extract) on
the attached graph paper.
Part B: Effect of Temperature
In the space below create a table for your results.
Plot a graph of rate of reaction (final foam volume) vs. the temperature on graph paper or using
excel
4
Conclusion
On the attached lined paper write brief statements summarizing how the factors you studied in this
lab influence catalase enzyme activity. Also comment on whether your hypothesis was correct.
Discussion
*Complete these questions on lined paper or in excel.
1.
a) For Part A, account for the shape of your graph. Be sure to use 4 technical terms to
account for the conditions under which the enzyme functioned well or did not function well. [4
marks A]
b) What are the independent and dependent variables in Part A? [2 marks A]
c) List two controlled variables in Part A. [2 marks A]
d) Identify two sources of error that may have affected your results. [2 marks T/I]
e) How could this procedure be modified to make this experiment more accurate in a
quantitative way? [2 marks T/I]
2.
For Part B, account for the shape of your graph. Be sure to use 4 technical terms to account
for the conditions under which the enzyme functioned well or did not function well. [4 marks
A]
3.
In a lab, students observed the following: 2mL of diluted potato extract was added to 8.0 mL
of 3% H2O2, a reaction occurred, producing foam for 3.5 minutes, then it stopped. Another
8.0mL of H2O2 was added to this mixture. The reaction proceeded again, producing foam for
approximately 3.6 minutes. Explain these observations. (3 marks T/I)
4.
The following chart provides information obtained for the activity of different digestive
enzymes at various pH levels. Plot graphs of rate of reaction vs. pH for this data. (use graph
paper attached) (4 Marks-A)
pH
Pepsin Reaction Rate (micromoles
of product produced)
1
2
3
4
5
6
7
8
9
10
11
12
13
140
278
136
12
3
0
0
0
0
0
0
0
0
Trypsin Reaction Rate
(micromoles of product
produced)
0
0
0
0
3
42
274
320
135
11
2
0
0
At what pH does each enzyme work the best? Explain why they react best at a certain pH.
Hint: review your notes to see where these enzymes act in the body. [2 marks A, 2 marks T/I]
5
ENZYME LAB EVALUATION
This evaluation sheet should be handed in with your lab.
Please use this to ensure you get the best possible mark.
Lab Report:
Part A Graph (includes: title, labels for axes,
appropriate scale, accurate graphing)
Part B Graph (includes: title, labels for axes,
appropriate scale, accurate graphing)
Conclusion-summarizes how the factors
studied influenced enzyme activity
Discussion Questions
/4 (A)
/4 (A)
/3 (T/I)
/18 (A)
/9 (T/I)
Communication in Lab Report:
Level 1
Level 2
Level 3
Level 4
- demonstrates
limited use of writing
conventions
-uses scientific
vocabulary and terms
with limited
effectiveness
-Charts demonstrate
limited effectiveness
(are poorly organized
and had to
understand)
- demonstrates some
use of writing
conventions
-Uses scientific
vocabulary and terms
with some
effectiveness
-Charts are somewhat
organized, but
sometimes difficult to
understand
- demonstrates
considerable use of
writing conventions
-Uses scientific
vocabulary and terms
with considerable
effectiveness
-Charts are well
organized and easy to
understand
- demonstrates thorough
use of writing
conventions
-Uses scientific
vocabulary and terms
with considerable
effectiveness
-Charts are
exceptionally organized
and easy to understand
Mark (C)
/10
Lab report performance rubric
Level 4
Locates and uses
equipment correctly all
of the time. Pre-lab was
completely finished.
Finished in the time
allowed, stayed on task,
followed all written and
oral instructions.
Follows safety
measures during lab
(goggles, hair tied back
etc.) all of the time.
Level 3
Locates and uses
equipment correctly
most of the time.
Level 2
Locates and uses
equipment correctly
some of the time.
Level 1
Does not use
equipment correctly
during the experiment.
Finished in the time
allowed, stayed on task,
followed all written and
oral instructions.
Required extreme
coaching to finish in the
time allowed and/or did
not follow some written
and oral instructions.
Did not finish in the time
allowed, and/or did not
follow written and oral
instructions.
Follows most safety
measures during lab
(goggles, hair tied back
etc.)
Follows some safety
measures during lab
(goggles, hair tied back
etc.)
Mark (A)
/10
Does not follow safety
measures during lab
(goggles, hair tied back
etc.)
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