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Biology
Unit 1
Identifying Enzymes
Name :_________Class
Set ____________________
Date:____________
Period:____________
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 (KAT-uh-LAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless
substances--water and oxygen. The reaction is as follows:
2H2O2 --------------------> 2H2O + O2
This reaction is important to cells because hydrogen peroxide (H 2O2) is produced as a byproduct 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.
Objective
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Measure the effects of changes in temperature and pH, on reaction rates of an enzyme-catalyzed reaction in a controlled
experiment.
Explain how environmental factors affect the rate of enzyme-catalyzed reactions.
Materials
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0.1molar HCl solution
0.1molar NaOH solution
6 Test tubes and Test tube holder
40 ml 3% Hydrogen peroxide solution (found in
stores)
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Stirring rod
Potato slush
Scissors and Forceps (tweezers)
10-ml Graduated cylinder
Thermometer
(3) 250 ml Beakers
ruler
Formulate two hypotheses based on Temp and pH of Enzymes.
Procedure (Part A) – The Effect of Temperature on Catalase Activity
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Obtain 6 test tubes. Fill 3 of the test tubes with 2 ml of hydrogen peroxide.
For the remaining 3 test tubes measure 2 ml of water, add to the test tubes. Mark the test tubes where the water line is.
Dump out the water.
In the 3 marked test tubes add potato slurry until it reaches the marked 2ml line.
Place 1 hydrogen peroxide tube & 1 potato tube in a hot water bath (100°C)
Place 1 hydrogen peroxide tube & 1 potato tube in an ice bath (0°C)
Place the remaining 2 test tube in a test tube rack at room temperature.
WAIT 3 MINUTES!!!!
Pour each tube of hydrogen peroxide tube into the corresponding temperature potato test tube.
Measure and record the rate of the reaction in the data table below.
Temperature
Ice Bath (0°C)
Room Temp (24°C-37°C)
Hot Bath (100°C)
Rate of Reaction (Height in
millimeters)
Procedure (Part B) – The Effect of pH on Catalase Activity
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Obtain 1 acidic test tube (pH 3), 1 basic test tube (pH 10), and 1 neutral test tube (pH7) from your teacher with 2 ml of each
solution. CAUTION: Do not let acids or bases contact your skin or clothing.
For the remaining 3 test tubes measure 2 ml of water, add to the test tubes. Mark the test tubes where the water line is.
Dump out the water.
In the 3 marked test tubes add potato slurry until it reaches the marked 2ml line.
WAIT 3 MINUTES!!!!
Pour each tube of hydrogen peroxide tube into the corresponding pH potato test tube.
Measure and record the rate of the reaction in the data table below.
pH
Rate of Reaction (Height in
millimeters)
Acidic (pH 3)
Neutral
Basic (pH 10)
Rubric:
Problem: Purpose written in a question form.
Hypothesis: Educated guess on what you think is going to happen in the experiment. (You
will have two hypotheses.)
Variables:
Independent variable (IV) (You will have two IVs, one for each hypothesis)
Dependent variable (DV)
Control group
Constants (at least 3)
Analysis/Data:
Data Tables
(Which must include an appropriate title which says what the graph/table is showing for
graphs title should include the IV and DV)
Graphs: Make two bar graphs of your data for Part A and Part B.
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Size must be 10cm x 10cm
Pencil and ruler used (keep it neat)
X and Y axis labeled with units included
Trend listed under the graph (discussion of the trend of the data seen in the graph; do
not restate the title)
Must include an appropriate title
Conclusion (CER)
Claim: A short concise answer to your problem
Evidence: Discussion of data (includes specific numbers collected during experiment recorded
in data tables and graphs.)
Reasoning: Justification that links your claim to your evidence. (Look at notes from lecture or
in biology text book)
The following questions need to be answered in complete sentences before your CER.
1. What gas is being released to reveal the dependent variable?
2. What reaction is happening in your test tubes? Be specific.
3. Describe the 3 reactions for pH and temp.
4. What is the optimal temperature for your catalase?
5. Why did some reactions not work? What happen to the catalase during these reactions?
6. What is the optimal pH for your catalase?
7. What is the effect of the low or high pH on the enzyme activity?
8. What would happen if we replaced H202 hydrogen peroxide with water (H20)? Explain your answer. Be specific.
9. What would happen to the cell if it produced too much substrate and not enough catalase? Explain your
answer?
10. If we added more hydrogen peroxide H2O2, theoretically would the reaction occur again? (catalase is an enzyme)
Please Note points can be deducted from the total of any lab grade for the following
infractions (5 points each):
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Not following the order of the lab write up
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Not including Title of the Lab
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Not updating Table of Contents