Year 12 Induction
WALT…
 …you will be doing an activity based on a previous
AS Biology ISA
 This will be a realistic “taste” of what your year
12 lessons will be like.
 You should take today seriously…
 …just like you should take your AS lessons
seriously.
WILF…
 Based on today’s session, you will be given an
assignment to do before you return in September.
See slide 13
 Please bring your completed assignment with you to
the Induction Day in September
 Sensible students will complete this at the earliest
opportunity!
 Beware: failure to hand in this assignment on 4th
September may count against you…
 …You may as a consequence be refused entry onto
the AS Biology course…
You will be investigating…
 The effect of substrate concentration on the
rate of an enzyme-controlled reaction
 Catalase is an enzyme found in many tissues. It
catalyses the reaction in which hydrogen peroxide
breaks down into water and oxygen. The oxygen is
given off as a gas.
catalase
hydrogen peroxide

water + oxygen
 In this task you will investigate the effect of different
concentrations of hydrogen peroxide on the rate of
this reaction.
Materials: Check list…
 Hydrogen peroxide
 100cm3 of water
 5 cm3 of plant extract
(catalase)
 Pipettes or measuring
cylinders
 Five boiling tubes and a
rack
 Marker or chinagraph
pencil
 Forceps
 Stopwatch
 Glass rod
 Petri dish or lid for
waste
 25 pieces of absorbent
card
20 second Round Robin:
As a group, repeat from memory your materials…
Method 1: Making dilutions…
 Make up five boiling tubes each containing 40cm3 of a different
concentration of hydrogen peroxide.
 The table shows the volume of hydrogen peroxide and the
volume of water to add to each tube.
Percentage
concentration of
hydrogen peroxide
Volume of
hydrogen
peroxide / cm3
Volume of water
/cm3
100
40
0
80
32
8
60
24
16
40
16
24
20
8
32
Method 2: Run the reaction…
1. Use the forceps to dip a piece of card into the
extract containing the enzyme. Watch the card go
darker as the extract soaks in.
2. Remove the card from the extract and shake off any
surplus liquid.
3. Drop the card into the boiling tube containing 100%
hydrogen peroxide. It should fall to the bottom of
the tube.
4. As soon as the card is at the bottom of the boiling
tube start your stopwatch. Record on your table the
time taken for the card to rise to the surface.
Magic? Why does the disc rise to the surface?
Method 3: Repeats…
5. Remove the card and put it in an empty Petri dish.
6. Repeat once more with 100% H2O2
7. Repeat steps 1 to 6 for each of the other four
concentrations of hydrogen peroxide.
Normally you would decide for yourself how
many times to repeat the experiment at each
concentration of hydrogen peroxide.
How many times should you repeat a
measurement like this? Discuss…
Note: “One repeat” means do it twice!
Results table…
Percentage of
H2O2 (%)
Time taken for disc to rise to the
surface (seconds)
First run
Should you do a
third (or
fourth…) repeat?
First repeat
100
80
60
40
20
Once you have the correct number of results for
each concentration, what would you do next…?
How would you handle anomalous results…?
Graph: On white boards…
Draw and label axes for the IV & the DV, with units.
Using the values below, include approximate scales
Plot the values
Draw a line of best fit
(4 marks)
Percentage of
H2O2 (%)
Mean time taken for
disc to rise to the
surface (seconds)
100
18
80
40
60
64
40
79
20
107
You
should
have
something
like this…
All write…
Describe
and explain
this graph
(5 marks)
AfL: Swap and peer assess…
 As the concentration of hydrogen peroxide
increases, the time taken for the disc to rise to the
surface decreases
 This is an inversely proportional relationship
 This is because as the amount of H2O2 (substrate)
increases, oxygen (product) is produced more
quickly
 The oxygen gas collects more quickly on the disc
 Causing the disc to rise to the surface in less time
Assignment…
Using the websites below, create an illustrated fact sheet
(preferably A3) on Enzymes.
 http://www.spolem.co.uk
 http://www.biologymad.com
 www.kscience.co.uk/resources/ks5/as/enzymes/enzyme
s.doc
 http://kingsfieldbiology.wikispaces.com/file/detail/Enzym
es+KS5.ppt
 http://www.biology-innovation.co.uk/
Remember you are to hand this in on your next Induction Day in
September
Thank you
and see you in
September!