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Transcript
Name: ____________________
ENZYME FUNCTION
LAB 9
PURPOSE
To explore the role of enzymes in chemical reactions.
INTRODUCTION
Enzymes are some of the most important kinds of molecules found in living cells. Cells could not function
without enzymes. They control the chemical reactions of the cells.
To understand how enzymes work, you will be observing some simple chemical reactions with hydrogen
peroxide. you may have hydrogen peroxide in your medicine cabinet at home. It is commonly used as a
bleaching and disinfecting agent.
Hydrogen peroxide has the chemical formula H2O2. Notice the similarity between this formula and the
formula for water, H2O. Hydrogen peroxide is an unstable compound, which turns into water by the
following reaction:
2H2O2 ─────────────> 2H2O +
Hydrogen peroxide
Water
O2
Oxygen
Hydrogen peroxide is stored in a brown bottle to deep out light, which speeds up this reaction.
Certain chemicals can also dramatically increase the speed at which this reaction takes place.
In this lab you will work with some of them.
Caution: Be careful not to get the hydrogen peroxide on your skin or your clothes. It is
powerful bleach.
Enzymes are proteins that speed up chemical reactions because they have a three-dimensional shape
that accommodates their substrate(s), the reactant(s) in the reaction. This shape, therefore, determines
the specificity of the enzyme and is important to the action of the enzyme. Various factors such as pH
and temperature can denature enzymes and cause them to lose their effectiveness. Today's laboratory
experiments will test the action of enzymes and the factors that affect their activity.
CATALASE
Catalase is an enzyme present in cells that speeds up the breakdown of hydrogen peroxide, a toxic
chemical, to water and oxygen:
2H2O2 ────────────> 2H2O & +
O2
Hydrogen peroxide
water
Oxygen
As the reaction occurs, effervescence develops that is easily observable.
27
For the experiments below, record your results in the following manner:
Results
Record
No effervescence
0
Moderate effervescence
+
Good effervescence
++
Very good effervescence
+++
MATERIALS
LIVER OR POTATO
3 TEST TUBES
TEST TUBE RACK
MORTAR AND PESTAL
EYE DROPPER
PROCEDURE
HYDROGEN PEROXIDE
HYDROCHLORIC ACID
SODIUM HYDROXIDE
SAND
A: : Surface area on Enzyme Activity:
Label and mark off three test tubes at 4 cm. Fill each to the mark with H 2O2. To the first tube, add a
pinch of sand; to the second, add a 1 cm piece of fresh liver or potato and to the third, a macerated cube
of liver/potato. To macerate the liver/potato take a 1 cm piece, place in a mortar, and grind with a pestle;
pour off the contents into the tube of H2O2. Record and explain your results.
Tube
Contents
Results
Explanation
1
2
3
B: Effect of pH on Enzyme Activity
Label and mark off three test tubes at 2 cm and 7 cm. Fill as follows:
Tube 1
Add water to the first mark and one cube of macerated Tissue. Wait 3 minutes. Add H2O2 to the second
mark. Record your results in the chart provided.
Tube 2
Add HCL to the first mark. Add one cube of macerated Tissue. Wait 3 minutes. AFTER WAITING, add
H2O2 to second mark. Record your results.
Tube 3
28
Add NaOH to the first mark. Add one cube of macerated Tissue. Wait 3 minutes.
AFTER WAITING, add H2O2 to the second mark. Record your results.
CAUTION: HCL is a strong caustic acid and NaOH is a strong base. Exercise care in
using these chemicals and follow the instructions of your instructor as to the disposal of
these tubes. If any acid or base should spill on your skin rinse immediately with clear water.
Tube
Contents
Results
Explanation
1
2
3
C: The Effect of Temperature
Design an experiment to test if heating destroys the enzyme catalase.
procedure and observation. Point form is acceptable.
Describe fully your
ANALYSIS
What two products does hydrogen peroxide change into when it breaks down?
What effect does a catalyst have on this chemical reaction?
What do you think causes the bubbling in this reaction?
What is the function of an enzyme?
What enzyme acts on hydrogen peroxide in living organisms?
Would this enzyme act on chemicals other than hydrogen peroxide? Why or why not?
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