ENZYME EXPERIMENT
You will investigate enzymatic activity in this experiment. There are two parts in the
experiment. In Part A, you will observe activity of chemical catalyst and biological
catalyst. In Part B, you will investigate the effect of temperature on catalase enzyme
activity. Before you start you should answer the following questions.
Pre-lab Questions:
1. What is a catalyst?
2. What is an enzyme?
3. How do enzymes work?
4. Why is an enzyme’s structure important for its function?
5. How can changes in temperature alter the structure of an enzyme?
6. What role do enzymes play in the body?
Background Information
Enzymes are proteins that act as biological catalysts. They help chemical reactions
proceed more easily in the bodies of organisms. Hydrogen peroxide is produced naturally
in organisms, but is very harmful. Catalase and other enzymes help break hydrogen
peroxide into water and oxygen gas. The bubbling that you may see if you pour hydrogen
peroxide on a cut is the oxygen gas produced from catalase activity. Enzymes, including
1
catalase, have very specific structures that help them bind with their substrate and
complete the chemical reaction. Changes in temperature and other environmental
conditions can alter the structure of a protein. If an enzyme changes its structure, it may
no longer work. In this experiment, the student will work to determine the temperature at
which catalase denatures and is no longer active. Raw potatoes and liver will act as the
tissue samples. Catalase activity will be estimated based on the amount of oxygen
bubbles produced.
H2O2
Catalyst
H2O + O2
PART A:
Aim: To observe chemical catalyst and biological catalyst of hydrogen peroxide.
The teacher will demonstrate Part A. In order to carry out Part B experiment you should
observe teacher’s demonstration very carefully and record your observation.
1- Put 5 ml of drinking water into a test tube and add 2ml of potato solution,
which contains the biological catalyst (catalase) of H2O2. Record your
observation on data table.
2- Put 5 ml of 6 % H2O2 into a test tube and add 2ml of drinking water. Record
your observation on data table.
3- Put 5 ml of 6 % H2O2 into a test tube and add 1gr of MnO2 which is the chemical
catalyst of H2O2. Record your observation on data table.
4- Put 5 ml of 6 % H2O2 into a test tube and add 2ml of potato solution which
contains the biological catalyst (catalase) of H2O2. Record your observation on
the data table.
5- Put 5 ml of 6 % H2O2 into a test tube and add 2ml of chicken liver solution, which
contains the biological catalyst (catalase) of H2O2. Record your observation on
the data table.
Data Table: Part A
Test tubes
1- H2O + potato solution
5pts
Observations
2- H2O2 + H2O
3- H2O2 + MnO2
4- H2O2 + potato solution
5- H2O2 + liver solution
2
Questions of Part A:
1- Is there any reaction in the test Tube 1? Why?
3pts
2- Is there any reaction in the test Tube 2? Why?
3pts
3- Is there any reaction in the test Tube 3? Why?
3pts
4- Is there any reaction in the test Tube 4? Why?
3pts
5- Is there any reaction in the test Tube 5? Why?
3pts
6- Write the name of the substrate and enzyme in the test tube 4 and 5. What are the
products in this reaction?
4pts
3
PART B: Effect of temperature on catalase activity.
Research Question:
Hypothesis:
Independent Variable: ………………………………………..
Dependent variable: …………………………………………….
Control Variables: ……………………………………………….
Materials:
1 large beaker (300 ml)
500 ml beaker for ice bath
thermometer
ice cubes
1 stop watch
1 stand, 1 clamp
1 test tube with stopper and plastic tube
4 plastic pipettes
2 graduated cylinder (10 ml)
300 ml potato solution
200 ml 6 % H2O2
Method:
1- Get one stand, one test tube clamp, one 300 ml beaker, a test tube with stopper,
which is connected by a 20 cm plastic tube.
2- Get 300 ml potato stock solution and 200 ml 6 % H2O2 solution, 4 clean plastic
droppers, two 50 ml graduated cylinders and masking tape/marker to label the
graduated cylinders as H2O2 and potato solution.
3- Measure the room temperature and record it on the data table.
4- Set up the test tube and stand as teacher showed in Part A.
5- Put 250 ml of tap water into 300 ml beaker.
6- Insert the free end of the plastic tube into tap water.
7- Measure the temperature of the room and record it. Measure 5 ml of 6 % H2O2 by
using graduated cylinder labeled as H2O2 and put it into test tube.
8- Measure 2 ml of potato stock solution by using graduated cylinder, which is
labeled as potato solution.
9- Add potato solution on H2O2 in the test tube and close it by rubber stopper
immediately.
10- Wait for 5 second and count the bubbles, which is in the water for 3 minutes.
Record it.
11- Rinse the test tube and repeat steps 7-10 for 2 times.
12- Put the ice cubes and water in a large beaker and make a water bath which is
0-1C0 .
4
13- Measure 5 ml of 6 % H2O2 by using graduated cylinder labeled as H2O2 and put it
into test tube.
14- Measure 2 ml of potato stock solution by using graduated cylinder, which is
labeled as potato solution.
15- Place both potato solution cylinder and H2O2 in the ice water bath and wait for 5
minutes.
16- Add cold potato solution on the cold H2O2 in the test tube and close it by rubber
stopper immediately.
17- Wait for 5 second and count the bubbles, which is in the water for 3 minutes.
Record it.
18- Rinse the test tube and repeat the steps 12-17 for 10 C0, 15 C0, 20 C0.
19- Measure 5 ml of 6 % H2O2 by using graduated cylinder labeled as H2O2 and put it
into test tube.
20- Measure 2 ml of potato stock solution by using graduated cylinder, which is
labeled as potato solution.
21- Adjust the temperature of solutions by using hot water bath which are at 30 C0,
35C0. 40 C0, 45 C0, 50 C0, 55 C0.
22- Wait for 5 second and count the bubbles, which is in the water for 3 minutes.
Record it.
23- Be sure you record all data that you collected.
Data Table:
Temperature
C0
1
10
15
20/ room
25
30
35
40
45
50
55
1st trial
# of bubbles /3min
2nd trial
# of bubbles /3min
Average
# of bubbles /3min
Data Processing.
Conclusion and Evaluation.
5