Enzymes
Practical 1
Introduction
Hydrogen Peroxide
o____________________
will break down into water and
oxygen very slowly at room temperature
Manganese dioxide
 ____________________
catalyst
is a _________
which
speeds up the breakdown of Hydrogen peroxide
Biological catalyst which
o____________
Catalase is a _________________
speeds up the breakdown of hydrogen peroxide.
Catalase is present in all living cells.
 To
show the effect of heating and catalysts
on the breakdown of hydrogen peroxide
 Set
up the apparatus shown in the diagram
Hydrogen
Peroxide

Hydrogen
Peroxide
+ Yeast
(catalase)
Water bath at 30o C
Hydrogen
Peroxide +
Manganese
dioxide
Hydrogen
Peroxide
Water bath at 90o C
 Note
the quantity of bubbles in each test
tube
 Record
table
your observations in your results
Tube
Contents
A
Hydrogen Peroxide
B
Hydrogen peroxide +
Catalase
C
Hydrogen Peroxide +
Manganese dioxide
D
Hydrogen Peroxide
Observation
No Bubbles
Many bubbles
Many Bubbles
Few Bubbles
 Which
two tubes are compared to show that high
temperatures speed up the breakdown of hydrogen
peroxide?
 ______________________________________
Tubes A and D
 Which
two tubes are compared to show that
catalysts speed up the breakdown of hydrogen
peroxide?
 _____________________________________
Tubes A and C
oWhich two tubes are compared to show that
biological catalysts speed up the breakdown of
hydrogen peroxide?
Tubes A and B
__________________________________________
 What
name is give to an experimental set up
which acts as a comparison
A control
 ________________________________
 Which
tube is used as a comparison in this
experiment
Tube A
 ___________________________________
Practical 2
 Learning

objectives:
By the end of the lesson you should be able to:


Explain that enzymes are specific to their substrate.
Describe why enzymes are specific to their substrate.
Specific
are _____________.
This means that
each enzyme can act on
Only one particular
_______________________.
substrate
Catalase
pepsin
 ______________
and _____________
are types
of enzyme.
 Enzymes
Egg white suspension is cloudy because it
o__________
Has large protein molecules
___________________________floating
in it
 To
show that enzymes are specific to
particular substrate
 Label
four test tubes A, B, C, and D and
prepare as below using SEPARATE DROPPERS
for each substance
 Tube A-5 cm3 hydrogen peroxide solution and
1 cm3 of catalase
 Tube B -5 cm3 hydrogen peroxide solution
and 1 cm3 of pepsin
 Tube C -5 cm3 egg white suspension and 1
cm3 of catalase
 Tube D- -5 cm3 egg white suspension and 1
cm3 of pepsin
 Place
your tubes in the water bath at 37oC
Examine the contents of the tubes A and
B for the presence of bubbles
Check the contents of tubes C and D to
see if they are cloudy or clear
Record your results in the table
Tube
Contents
Observation
A
Hydrogen peroxide + catalase
Bubbles
B
Hydrogen Peroxide and Pepsin
No bubbles
C
Egg white and Catalase
D
Egg white and pepsin
Cloudy
Clear
 Interpretation
 Which
substrate is acted on by catalase?
Hydrogen Peroxide
 _________________________
Which substrate is acted on by pepsin?
Egg White
___________________________________
 What
do these results suggest about the
specificity of enzymes?
Enzymes act on only one substrate , so are said to be specific
 ________________________________
 Name
2 of the variables which are
controlled to make the experiment valid?
Volume of enzyme
Volume of substrate
 _____________________________________
Temperature
Time
 ____________________________
Practical 3
 Learning


objectives:
By the end of the lesson you should be able to:
Describe how temperature effects enzyme
activity
 Enzymes
Are made of protein
_______________________
o The enzyme ______________
Catalase
is found in all living
tissue. It catalyses the reaction
If a little detergent is added to the hydrogen
peroxide solution a foam is formed by the oxygen
gas given off during the reaction.
height of the foam gives
 The ___________________an
indication of
Enzyme activity
____________

o Egg white contains protein molecules which are
affected by temperature
 To
show the influence of temperature on
enzyme activity.
 You
will be split into groups with each
group carrying out the experiment at
different temperatures and the results will
be pooled.
1
Label 3 test tubes A, B and C and
prepare as below



Tube A Tube B Tube C -
3cm3 egg white
5cm3 hydrogen peroxide
Piece of potato tissue
3 Set up a beaker water bath (Your teacher will tell
you the temperature) and place all three tubes in
the water bath. You must keep the temperature
constant throughout the experiment.
4 Leave for 10 minutes
5 Carefully add the hydrogen peroxide to the test
tube containing the potato tissue.
6 Leave for a further 10 minutes
7 Note the appearance of tube A and measure the
height of the foam above the liquid in tube C.
8 Pool the results from all groups in the table.
Temperature (oC)
Height of foam (mm)
Egg white
appearance
0
10
Clear
34
21
clear
79
4.5
cooked
 Draw
a line graph of results
Height of
foam
(mm)
Temperature (oC)
 What
is the relationship between the
enzyme activity and temperature.
40 oC
 As the temperature rises to ____
enzyme activity increases.
40 oC enzyme activity decreases
Above ____
 The
optimum temperature for the enzyme
40 oC
is ___
 Why
are the hydrogen peroxide and
potato left in the water bath for ten
minutes before being added together?
 To
allow them to reach the experimental
temperature
Practical 4
 Learning


objectives:
By the end of the lesson you should be able to:
Describe how pH effects enzyme activity
 Introduction
pH values
 ________
indicate the level of acidity and
alkalinity of a solution
 When
universal indicator is added to a solution
Changes colour indicating the pH value
it _____________________________________
Red
0
Orange/Yellow
Green
3 4 5 6
7
1 2
Acid
Neutral
Grey
Blue
8 9 10 11 12
Alkali
13 14
 Pepsin
is an enzyme found in the human
stomach which catalyses the reaction
Protein
Pepsin
Peptides
Source of protein It is
white is a ______________.
cloudy because of the large protein
molecules floating in it.
 Egg
To
show the influence of pH on
enzyme activity
 1.
Label three test tubes A, B, C
 2. Using separate droppers, add to each
tube 3 cm3 egg white and 3 cm3 pepsin
solution.
 3. Use separate droppers to now add
 4. Place the tubes in a water bath at 37oC
for 20 minutes.
1 cm3 of acid to A
 1 cm3 of water to B
 1 cm3 of alkali to C

 5.
Note the appearance of each tube and
then determine the pH by adding a few
drops of universal indicator.
Tube
pH
Egg white
appearance
A
Acid
CLEAR
B
Neutral
CLOUDY
C
Alkaline
CLOUDY
 Under
which pH conditions is pepsin
active?
Acid conditions only
 _______________________________
 How
could you improve this experiment to
find the optimum pH for the enzyme
pepsin? (Hint: Is pepsin equally active at
all pH values?)
 Set
up a similar experiment using a
range of pH values
Practical 5
 Learning

objectives:
By the end of the lesson you should be able to:

Explain that enzymes can be involved in making
substances.
 Phosphorylase
is an enzyme found in potato
tubers which catalyses the build up of starch
from glucose-1-phosphate
Glucose-1phosphate
phosphorylase
Starch
 Potato
extract is liquid from the potato tuber
Contains the enzyme but no starch
which ________________________
Iodine
for the presence of starch
o______solution
is used to Test
____________
Black
oIt turns _____________
when starch is present
 To
demonstrate the action of the enzyme
phosphorylase
 Your
teacher will set up a dimple tile as
shown in the diagram
Column 1
Column 2
Column 3
Column 4
Row A
g-1-p
P
g-1-p
P
g-1-p
P
g-1-p
P
Row B
g-1-p
DW
g-1-p
DW
g-1-p
DW
g-1-p
DW
Row C
P
DW
P
DW
P
DW
P
DW
Glucose -1phosphate = g1-p
Distilled water =
DW
Phosphorylase = P
Add iodine to each dimple as follows
Column 1 after 5 minutes
Column 2 after 10 minutes
Column 3 after 15 minutes
Column 4 after 20 minutes
 What
is produced in row A?
Starch
 ______________
 What
two substances are present where
this is produced?
The enzyme phosphorylase
 ___________________________________
The substrate
Glucose-1-phosphate
 ____________________________________
 Why
is row B set up?
 _____________________________________
As a control to show that glucose-1phosphate can not produce starch on its own
_________________________________________
 Why
is row C set up?
As
_____________________________________
a control to show that phosphorylase can not
produce starch on its own
________________________________________