Dulwich International High School Suzhou
AS Biology Practical
Experiment 1: Effects of pH, temperature (T) and substrate concentration [S] on enzyme
activity.
Student Name: _______________________
Instruction for Teacher:
Please use whole or part of this practical manual to suit with your teaching objectives
and class time.
Please communicate with laboratory technicians to fully prepare and equip the
laboratory before start of the lesson.
Please ensure personal protective equipment (PPE) is available and accessible to all
individuals present during the lesson at all times.
Safety liability is solely borne by the teacher in the laboratory during the lesson.
Instruction for Technician:
Please prepare all materials (see below) in individual sets for all students before the
start of the lesson. Please ask the teacher how many sets are required.
It is your responsibility to share and communicate information of hazardous materials
and safety protocols with the teacher and students.
Please ensure safe handling of materials.
Materials:
Each group is equipped with 1 set of materials consisting of the following contents.
One Potato
One cutting board and two knives
50 ml hydrogen peroxide
Five 50 ml Beakers
100 cm3 measuring beaker
Liquid soap (shared)
One timer
Ten boiling tubes
Cork borers (to make potato cylinders)
One test tube rack
pH solutions (pH 4 and pH 10)
Water bath (shared)
One stop watch
30cm ruler
1|Page
Dulwich International High School Suzhou
AS Biology Practical
Instruction for Student:
Personal protective equipment (PPE) must be worn at all time.
Please read ALL of the practical manual carefully before starting the practical.
Please ensure you have and are able to access all materials on your bench or inside the
laboratory.
Please ensure you are fully aware of the hazards associated with each material before
you start handling them.
Please finish all experimental procedures and collect data within the time given by your
teacher.
Background:
Peroxidase is an enzyme that breaks down Hydrogen Peroxide (H 2O2). All cells create H2O2 as a
by-product of cellular reactions. However, it is a highly toxic compound and must be neutralized
to ensure the cells survival. Living cells produce an enzyme called catalase that quickens the
breakdown of a damaging substance called hydrogen peroxide. The following word equation
summarizes this reaction:
Hydrogen peroxide —> oxygen + water
The activity of catalase can be measured when in a solution because bubbles of oxygen gas are
produced - visible as foam. When the catalase solution is added to the hydrogen peroxide
solution and left for a set period of time (e.g. one minute) the height that the foam reaches in
the test tube can be measured using a ruler.
2|Page
Dulwich International High School Suzhou
AS Biology Practical
Methods:
Carry out the following steps for either different pH or temperature or hydrogen peroxide
concentration as assigned by your teacher at the start of the lesson.
1. Make a 1cm long potato cylinder.
2. Set up the measuring cylinder with 5cm3 of H2O2.
3. Add a drop of liquid soap into the H2O2 and mix GENTLY!!
4. Add one potato piece to the H2O2/soap mixture and time for 30 seconds.
5. Record the level of foam produced within 30 seconds using a stop watch.
6. Repeat 4-5 with the two other pieces of potato to get 3 results.
7. Calculate the average height and Rate of Reaction
8. Repeat steps 1-10 for four other sizes.
9. CLEAN UP!
Results:
Create an appropriate table to collect your data (THIS IS ALWAYS IN THE P3 EXAM, SO THINK
CAREFULLY!)
3|Page
Dulwich International High School Suzhou
AS Biology Practical
Design and draw an appropriate graph of your results with the graph paper below:
Discussions: (Describe your results and explain what they tell you here)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4|Page
Dulwich International High School Suzhou
AS Biology Practical
Describe anything you observed that was unusual or that you found different.
What could you do to improve the reliability of the results?
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exam-type question:
The enzyme, catechol oxidase, causes a brown color to develop when slices of many fruits, such
as apples, are exposed to air.
The enzyme catalyzes the following reaction:
Catechol + oxygen → quinone + water
Quinone is then immediately further oxidized in air to a brown-colored substance. Catechol and
quinone are colorless.
1. A student investigated the rate of this reaction under different conditions. Suggest how
the student could follow the progress of this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. Lemon juice contains citric acid. Adding a small amount of diluted lemon juice to apple
slices slows the appearance of the brown color. Suggest an explanation for this
observation.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5|Page