Name: __________________________________
Date: _______________
Period: _____
An Investigation of the Enzyme Catalase
Introduction:
Enzymes are catalytic proteins that speed up the rate of chemical reactions that would otherwise happen more slowly.
A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction. Enzymes
bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of
activation energy needed and thus speed up the reaction. Not only do enzymes economize energy usage, but also
provide a variety of other functions. You have hundreds of different enzymes in each of your cells. Each of these
enzymes is responsible for one particular chemical reaction that occurs in the cell.
In this lab you will study catalase, an enzyme that is found in the cells of many living tissues. Cells use the enzyme
catalase to rid itself of a poisonous substance (hydrogen peroxide) by breaking it down into two harmless substances
(water and oxygen). The rate of this reaction can be determined by measuring the amount of oxygen is produced. Filter
paper disks soaked in different catalase solutions react at different speeds. In all cases, however, the catalase reacts
with the hydrogen peroxide and causes it to break down into oxygen and water. The oxygen builds up on the disk,
causing it to float. Depending on the catalase solution some of the reactions will happen faster than others, producing
oxygen faster and the disk will float sooner. In this lab you will measure the time it takes for a disc of filter paper,
soaked with different concentrations of enzyme, to make its way to the top of a plastic vial filled with hydrogen
peroxide. Rate of enzyme activity = distance (depth of hydrogen peroxide in mm)/time (in sec).
Catalase catalyzes the decomposition of hydrogen peroxide into water and oxygen. One molecule of catalase can
break 40 million molecules of hydrogen peroxide each second.
Catalase
2H2O2 -----> 2H2O + O2
You may be surprised to find out that hydrogen peroxide is produced as a waste product in every cell of your body. It is
a byproduct of many normal chemical reactions. If the cells did not break down the hydrogen peroxide, they would be
poisoned and die. In cells, the enzyme catalase works on its substrate (hydrogen peroxide) converting it to harmless
water and oxygen.
Objectives:
 Students will prepare various dilute solutions from a 100% enzyme solution.
 Students will determine how enzyme concentration affects reaction rate.
Materials:
6 medicine cups for dilutions, *catalase stock solution, clear plastic vial, forceps, 18 filter paper disks, Hydrogen
Peroxide (H2O2), paper towel, apron, safety glasses, watch with second hand, marker, metric ruler, calculator
* The enzyme has been prepared for you as follows: 50g of peeled potato was mixed with 50 ml cold distilled water
and crushed ice and homogenized in a blender for 30 seconds. This extract was filtered through cheesecloth and
cold distilled water was added to a total volume of 100 ml. Extract concentration is arbitrarily set at 100 units/ml.
ENZYME SHOULD BE KEPT ON ICE AT ALL TIMES!!
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Procedure:
1.
Make a series of dilutions of the enzyme catalase using the following table.
Final
Quantity
Needed
Concentration of Final Solution
mL of
Catalase
mL of
Water
10 ml
100%
10
0
10 ml
80%
8
2
10 ml
60%
6
4
10 ml
40%
4
6
10 ml
20%
2
8
10 ml
0%
0
10
2. Use a marking pencil or Sharpie and mark the enzyme solutions as follows: 100%, 80%, 60%, 40%, 20%, and 0%.
3. Fill a clear vial with 20 mL of hydrogen peroxide.
4. Using your forceps, pick up one filter paper disk and submerge it in the 100% enzyme solution for 5 seconds.
Continue to hold the disk with the forceps.
5. Remove the disk from the solution and blot it dry, for five seconds, using your paper towel.
6. Drop the disk in the hydrogen peroxide. Measure the time it takes for the disk to sink to its lowest point and
then rise up from the bottom to the surface (in seconds). Begin timing as soon as the disk touches the
surface of the hydrogen peroxide.
7. Use the metric ruler to measure the distance the disk sinks into the hydrogen peroxide. Multiply by two to
determine the entire distance the disk traveled. Enter the time and distance the disk traveled in the column
for Trial 1 in the data table below.
% Catalase
Time in seconds
Trial Trial Trial
1
2
3
Avg.
Distance in millimeters
Trial 1
Trial 2
Trial 3
Reaction Rate mm/s
Avg.
100
80
60
40
20
0
8. Repeat the above steps for the remainder of the solutions. Remember to use clean filter paper each time
you use a different solution. Enter the times and distances for trial 2 and 3 in their appropriate columns.
9. Follow your teacher’s directions for clean-up.
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Analysis & Conclusion:
1.
What was the enzyme in the lab?
2. What type of organic compound is catalase?
3. What was the substrate in the lab?
4. What were the products from the reaction?
5. Which concentration of catalase had the fasted reaction time?
6. Which concentration of catalase had the slowest reaction time?
7. What is catalase and why is it important to cells in your body?
8. How did you know that catalase was present in the above compounds?
9. Graph your data (see #13). Based on the graph and overall slope of the line, what can you conclude
about the effect of enzyme concentration on reaction rate?
10. What were some potential errors?
11. If you were to do this lab again, what could you do differently?
12. What other factors can affect enzyme activity?
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13. Produce a line graph of the above data. Use the enzyme concentration as the independent variable and the
reaction rate as the dependent variable.
Graph Title: __________________________________________________
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