Photosynthesis
Practical sheets
Photosynthesis

Learning objectives:
◦ By the end of the lesson you should be able
to:
 Describe what the glucose made during
photosynthesis is converted to.
Practical 1
Testing a leaf for starch
Introduction

Glucose
___________
made in green plants by photosynthesis is
Starch
stored in the form of _____________
Testing a leaf for starch is used to show whether of not
Photosynthesis
________________
has taken place
Black
The leaf will turn ___________
if starch is present.
Brown
If starch is absent the leaf will turn _____________
Leaves need special treatment before this test can be carried
out.
Aim

To carry out a starch test on a leaf
Method (a ) Leaf treatment
Step
Reason
Boil leaf in
water for 5 minutes
Heat destroys cell membranes and so
allows iodine solution in.
Use forceps to transfer
leaf to a boiling tube
containing alcohol
Alcohol removes:
Green chlorophyll, Waxy cuticle
To let iodine in
TURN OFF BUNSEN
Alcohol is flammable
Place tube in the beaker
of hot water.
Leave until the leaf is
discoloured.
To boil the alcohol
Starch test colour change will now be more
visible.
Remove the leaf and
rinse in the beaker of
hot water for 10 seconds
Softens that the leaf can be spread out.
Place leaf on a white tile
and cover with iodine solution.
The leaf will turn black if starch is present
Results
What colour does the leaf turn?
The leaf turns a black/brown colour
 ________________________________

Conclusion
What does the result show?
 ______________________________
That starch is present

Evaluation
What safety precautions are taken in this
experiment and why?
 Eye
__________________________________
protection is worn as liquids are being boiled

 __________________________________
Lit bunsen burners and ethanol are kept well
apart as ethanol is flammable
____________________________________
Practical 2
REQUIREMENT FOR
PHOTOSYNTHESIS
Photosynthesis

Learning objectives:
◦ By the end of the lesson you should be able
to:
 State the raw materials required for photosynthesis.
 Describe how the raw materials get into the plant
mentioning diffusion.
 Write a word equation for photosynthesis.
Introduction

Co2

The equation for photosynthesis is:
Water
Light
Energy
Chlorophyll
Glucose
Oxygen
Enzymes
starch
Glucose is stored in leaves as ________.
•If any one of the rawphotosynthesis
materials or requirements is
missing, then ___________ cannot occur and
________
starch cannot be made

A variegated leaf has some white parts which
Chlorophyll
lack ________________
Aim

To show that chlorophyll, Co2 and light are
essential for photosynthesis to occur.
Method
1.Your teacher will give you three leaves
 A – variegated and kept in the light
 B – kept in the light but without CO2
C – kept in the dark
 Draw an outline of each leaf in the “Before”
column in your results table and label
◦ The green areas of leaf A
3. Test all the leaves using the method outlined in
practical 1
4. Draw an outline of each leaf in the “After”
column and label the areas of the leaf that have
turned black
Results
Leaf
Appearance
Before
Appearance
After
A
B (No Co2)
C (No light)
Interpretation
 Which leaf shows that for starch to be made by photosynthesis.
a) light is necessary
Leaf C
__________________
b) Co2 is necessary
Leaf B
_________________
c) Chlorophyll
is necessary
Leaf A
______________________________

Conclusion
What requirements does this experiment show
are needed for photosynthesis to occur?
___________________________________

Light, Co2 and Chlorophyll
Evaluation
•What is possible source of error in this
experiment?
_______________________________
Keeping a leaf in a bell jar may also
prevent CO2 reaching the leaf
_______________________________