Enzyme-Catalyzed Reactions Lab
Name _______________________
Partner: _____________________
Partner: _____________________
Partner: _____________________
Introduction:
Enzymes are proteins that work as biological catalysts. Catalysts are substances that speed up chemical reactions. Enzymes either:
1. Catalyze the breakdown of a substrate molecule into products.
2. Catalyze the assembly of substrate molecules (monomers) into a larger product (polymer)
This lab will use the enzyme catalase and the substrate hydrogen peroxide.
The reaction:
H2O2 + catalase 
H20 + O2 + heat + catalase
Notice that catalase is not changed by the reaction, and that the reaction produces heat. Reactions that produce heat are called
exothermic. Hydrogen peroxide breakdown naturally but very slowly. Catalase makes the reaction thousands of times faster and
causes bubbling.
We will measure the reaction rate visually and assign a qualitative value;
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
All enzymes are proteins with active sites that have a shape that must exactly fit the substrate. Heat and strong acids can destroy the
shape of the active site and make the enzyme nonfunctional. This is called denaturing.
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Part I: Where is Catalase Found?
Hypothesis: If catalase is present in a food item, then the reaction will speed up.
Materials: dropper, potato, carrot, cracker, liver, salt, sugar, onion, well plate, dropper, forceps, H2O2.
Procedure:
Substance
1. Carefully place a small quantity of each material listed above in a well on the well plate.
2. Do not cross contaminate material – WIPE OFF FORCEPS
3. Add 5 drops of H2O2. to each well and record observations.
H2O2
potato
carrot
cracker
Liver
salt
sugar
onion
only
(control)
Reaction rate
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
Was the hypothesis above supported or refuted? Give evidence.
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Part II: What Effect Does Heat Have on Enzyme Function?
Hypothesis: If catalase is heated, then the amount of oxygen bubbles will decrease.
Materials: liver, 2 test tubes, hotplate, 2 beakers, water, grad. cylinder, test tube holder, H 2O2
Procedure:
1. Carefully place a small sized piece of raw liver in each of 2 test tubes.
2. Add 4mL of water (use dropper) to each test tube.
3. Place one test tube in the test tube rack. This is your control at room temperature
(21 degrees C).
4. Place the other test tube in a beaker of boiling water. This is your experimental test
tube (100 degrees C).
5. Let the liver cook in the water for 5 minutes.
6. Drain the water out of each test tube, being careful not to lose the liver pieces. DO NOT CROSS
CONTAMINATE!
7. Equalize the temperature of both test tubes by placing them in a beaker of cold water together for 3 minutes.
3. Add 3 mL of H2O2 to each test tube with the liver and observe.
Group
Control (raw)
Reaction rate
Experimental (cooked)
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
Was the hypothesis above supported or refuted? Give evidence.
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Part III: Does acid (change in pH) destroy an enzyme’s ability to speed up a chemical
reaction?
Hypothesis: If acid is added to catalase, then fewer bubbles of O2 will be produced.
Materials: dropper, liver, 2 test tubes, water, grad. cylinder, thermometer, test tube holder, H 2O2
Procedure:
1. Carefully place a small amount of liver in each of 2 test tubes.
2. Add 5mL of lemon juice (acid) to one tube (experimental)
3. Add 5 mL of water to the other test tube. (control)
4. Swirl both test tubes for 3 minutes.
5. Add 5 mL of hydrogen peroxide to each test tube.
5. Record your observations.
Group
Control (water)
Reaction rate
Experimental (lemon
juice)
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
Was your hypothesis supported or refuted? Give evidence.
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------------------------------------------------------------------------------------------------------------------Part IV: Can an enzyme be used up or reused?
Hypothesis: If an enzyme is used once, then it will have a reaction when used again.
Materials: dropper, liver, test tube, graduated cylinder, test tubes
Procedure:
Test Tube
1. Carefully place a small amount of liver in a test tube
2. Add 5ml of hydrogen peroxide
3. Record reaction rate (0-3).
4. Pour off liquid and leave the liver in the test tube.
5. Add 5 ml of NEW hydrogen peroxide to the same test tube & liver.
6. Record reaction.
Reaction rate
Trial 1
Trail 2
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
Was your hypothesis supported or refuted? Give evidence.
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Questions
1. Where is the enzyme catalase naturally found?
2. What is the function of catalase in living cells?
3. What happens to an enzyme's ability to catalyze a reaction when they are heated?
4. Describe what happens to the active site of enzymes when they are exposed to high temperatures or strong acids.
5. What effect does lemon juice have on catalase enzyme?
6. What is the substrate that catalase bonds with?
7. What is hydrogen peroxide changed into when catalase reacts with it?
8. Is catalase changed during the reaction?
9. What happens to enzymes when they are heated or exposed to acids?
10. Explain why hydrogen peroxide bubbles when you put it on a cut on your skin.