Name:
Period:
Enzymes and Chemical Reactions
Hydrogen peroxide is a chemical that is produced by cells as a metabolic waste. Hydrogen peroxide
is poisonous to living cells. To prevent the small amounts of hydrogen peroxide from building up to
toxic levels, cells must either export the poison or change it into substances, which are not harmful.
Liver cells produce relatively large amounts of an enzyme called catalase, which breaks down
hydrogen peroxide into harmless substances. The chemical formula for hydrogen peroxide is H2O2.
PART ONE
INTRODUCTORY PROCEDURE:
 Obtain 2 beakers. Label each beaker #1 and #2
 Do NOT throw away the materials until instructed.
1. Place 5 ml of water into a small beaker. (BEAKER 1)
2. Add a piece of liver to the water & record your observations. (LIVER 1)
3. Place 5 ml of H2O2 into a different small beaker. (BEAKER 2)
4. Add a piece of liver to the H2O2 & record your observations: (LIVER 2)
Beaker 1 (water and liver)
Beaker 2 (H202 and liver)
INTRODUCTORY QUESTIONS:
1. What is the chemical formula for water?
2. What is the chemical formula for hydrogen peroxide?
3. What happened in the beaker of liver and water?
4. What happened in the beaker of liver and hydrogen peroxide?
5. What are the most likely products of the breakdown of hydrogen peroxide?
(HINT: Reread intro & answers to # 1 & 2 of the intro questions)
DO NOT THROW AWAY ANY OF THE MATERIALS YET!!!
PART TWO:
OBJECTIVE:
PROCEDURE:
 Obtain 3 new beakers Label each beaker #3, #4, and #5
1. Put liver #1 into beaker #3
2. Add 3 ml of fresh H202 & record your observations.
3. Remove liver #1 and place in new beaker #4
4. Add 3 ml of fresh H202 & record your observations.
5. Remove liver #1 and put into beaker #5.
6. Add 3 ml of fresh H202 & record your observations.
Beaker 3
Beaker 4
Do enzymes get “used up?”
Beaker 5
**Clean all glassware w/ soap and water & return to materials station. Put liver in container
marked “LIVER” !! Liquids can be dumped into the SINK.
Don’t make a mess
FOLLOW UP QUESTIONS: Answer in complete sentences.
1. What do you think would happen if we were to add 3 ml of fresh H202 to the same piece of
liver again?
2. What property of enzymes has been illustrated in Part Two?
3. What could you do to take a quantitative measurement of your observations?
4. Define Catalyst:
5. Are enzymes catalysts? Why?
6. How do enzymes do that (in terms of energy?
7. What happens to the enzyme during the reaction?
8. What happens to the substrate during the reaction?
Use the following chart to draw & label how enzymes work:
9. What is the name of the enzyme that breaks down hydrogen peroxide?
10. Where is it located?
11. Why does it need to break it down?
12. What happened when you mixed the liver (enzyme) with water?
13. What happened when you mixed the liver (enzyme) with H2O2?
14. What happened when you added fresh H2O2 to a piece of liver that had already reacted
with H2O2?
15. Explain why & how this happened using your notes & answers from above.
16. How does temperature affect an enzyme’s abilities to perform its “job”? How does pH?
Temperature and Enzyme Activity
PROBLEM:
How do changes in temperature affect the effectiveness of enzymes?
MATERIALS:
Liver
Test tubes (3)
Hydrogen peroxide (12 mL)
Warm water bath (37 oC) CONTROL GROUP
Boiling water bath (100oC)
Ice water (3-4 oC)
Graph Paper
Prediction:
If the temperature of the enzyme increases then the effectiveness of the enzyme will
____________.
If the temperature of the enzyme decreases then the effectiveness of the enzyme will
______.
PROCEDURE:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Measure & place 1 mL of liver juice into test tube one.
Place test tube one into an ice bath.
Measure & place 1 mL of liver juice into test tube two.
Place test tube two into a warm (room temperature) water bath for 1 minute.
Measure & add 4 mL of hydrogen peroxide into test tube two.
Observe & record the height of the bubbles in mm on the data chart in TEST TUBE 2!
Measure & place 1 mL of liver juice into test tube three.
Place test tube two into a boiling bath of water for 1 min. (Wait for the water to reach a full rolling
boil before putting it in) USE TEST TUBE HOLDERS TO AVOID BURNS ON HANDS!!!
Measure & add 4 mL of hydrogen peroxide into test tube three.
Observe & record the height of the bubbles in mm on the data chart (Remember this is TEST TUBE
3!)
Retrieve test tube one from the ice bath.
Measure & add 4 mL of hydrogen peroxide into test tube one.
Observe & record the height of the bubbles in mm on the data chard (Remember this is TEST TUBE
1!)
DATA:
TEAM
TEST TUBE ONE
COLD WATER BATH
Height of bubbles (mm)
TEST TUBE TWO
WARM WATER BATH
Height of bubbles (mm)
TEST TUBE THREE
HOT WATER BATH
Height of bubbles (mm)
1
2
3
4
5
6
7
****Create a bar graph of your team’s data and of the class data on your own graph
paper & attach it to this paper. Use different colors for the different temperatures &
different patters for the different groups.
ANALYSIS and CONCLUSION: (Label as analysis and conclusion & answer on the back or bottom
of your graph paper.)
1. Did temperature effect the enzyme’s functioning? How? How do you know?
2. Discuss how temperature affects an enzyme’s abilities.
3. Discuss how this might affect living organisms.