1. 4.1 Sunlight and Starch Production
Today’s Learning Objectives:
 State the difference by which animals and plants
obtain food.
 State the source of energy used by plants to make
food.
 Define the term ‘photosynthesis’.
 Define the term ‘producer’.
 Define the term ‘carbohydrate’.
 Describe how to test a leaf for the presence of
starch.
 Compare photosynthesis in light and dark conditions
 Show how starch production varies over a normal
24-hour period.

2. Green plants as producers
Producers are green plants which make food
by photosynthesis.
Carbohydrates are molecules containing
carbon, hydrogen and oxygen.
Photosynthesis is a process in which green
plants make carbohydrate from raw
materials using energy from sunlight.

3. Raw materials from
environment
H2O CO2
Green plants
make
carbohydrate
Animals eat
plants
containing
carbohydrate

4. Investigation of the Requirements for
Photosynthesis
Light is required
for
photosynthesis
Uncovered areas turn
blue black in the
presence of iodine
Covered areas turn
brown in the
presence of iodine
Light
ConclusionResultExperimentRequirements
of
photosynthesis

5. 4.2 The Role of Chlorophyll
Today’s Learning Objectives:
 Name the green substance in plants needed for
photosynthesis.
 What is meant by a variegated leaf?
 Describe an experiment that shows that chlorophyll
is needed for photosynthesis.
 Name and describe the structures in a cell which
contain chlorophyll.
 State the role of chlorophyll in photosynthesis.
 State the energy change which takes place in
photosynthesis.
 Name the compounds in which the energy absorbed
during photosynthesis ends up.

6. Looking at Plant Cells
Pond weed cells Plant leaf cells packed
with chloroplasts
Chloroplasts contain the pigment CHLOROPHYLL

7. Investigation of the Requirements for
Photosynthesis
Chlorophyll is
required for
photosynthesis
Green areas turn blue
black in the presence
of iodine White
areas turn brown in
the presence of
iodine
Chlorophyll
Light is required
for
photosynthesis
Uncovered areas turn
blue black in the
presence of iodine
Covered areas turn
brown in the
presence of iodine
Light
ConclusionResultExperimentRequirements
of
photosynthesis

8. 4.3 Raw Materials and Products
Today’s Learning Objectives:
 Name the raw materials for photosynthesis.
 State the source of these raw materials.
 State what glucose is converted to for storage.
 Describe an experiment to show that carbon
dioxide is necessary for photosynthesis.
 Name the products of photosynthesis.
 Describe how green plants affect the composition
of gases in the atmosphere.
 Write a summary equation for photosynthesis.

9. Investigation of the Requirements for
Photosynthesis
CO2 is required
for
photosynthesis
No CO2 – brown in
the presence of
iodine
CO2 - black
Carbon Dioxide
Chlorophyll is
required for
photosynthesis
Green areas turn blue
black in the presence
of iodine White
areas turn brown in
the presence of
iodine
Chlorophyll
Light is required
for
photosynthesis
Uncovered areas turn
blue black in the
presence of iodine
Covered areas turn
brown in the
presence of iodine
Light
ConclusionResultExperimentRequirements
of
photosynthesis
CO2 No CO2

10. Summary Equation for Photosynthesis
Carbon dioxide
Water
+
Chlorophyll
Light Glucose
Oxygen
Raw materials Conditions Products

11. 4.4 Two Stages of Photosynthesis
Today’s Learning Objectives:
 Explain the term ‘photolysis’.
 Name the raw materials and products of photolysis.
 State the energy conversion which accompanies
photolysis.
 State what happens to the products of photolysis.
 Name the molecule which transfers energy to the
carbon fixation stage.
 Explain the term ‘carbon fixation’ and state where
the starting materials come from.
 State how carbon fixation is controlled and how the
energy needed is supplied.

12. Photosynthesis is more complicated than
the summary equation suggests…
The whole reaction has two separate
stages:
• Photolysis Stage
• Carbon fixation stage

13. 1. Photolysis stage
Photolysis is the process by which energy from sunlight
splits water molecules into hydrogen and oxygen
Light Energy
Chlorophyll
Chemical Energy
ADP + Pi
ATP
Water (H2O)
Hydrogen
Oxygen
+
Used in
stage 2
Used in
stage 2
Released
to air

14. 2. Carbon fixation stage
The process by which carbon dioxide is combined
with hydrogen to make glucose.
Glucose
Enzyme controlled
reactions
Hydrogen
From
stage 1
ADP + PiATP
From
stage 1
Carbon dioxide
From Air

15. 4.5 Starch and Cellulose
Today’s Learning Objectives:
 Name the small molecules that link together to
make starch and cellulose.
 State the function of starch in plant cells.
 State two properties of starch which make it
suitable for this.
 State the function of cellulose in plant cells.
 State two properties of cellulose which make it
suitable for this.
 Describe how starch is stored in cells.
 Describe the arrangement of cellulose fibres in cell
walls.
 Explain two properties of cell walls resulting from
the arrangement of cellulose fibres.

16. Potato cell with
starch granules
X 1100 magnification
Potato
starch grains
X 1000 magnification

17. Cellulose fibres in a cell wall

18. 4.6 Limiting Factors in Photosynthesis
Today’s Learning Objectives:
 Define the term ‘limiting factor’ in the context of
photosynthesis.
 Give three possible limiting factors in
photosynthesis.
 Describe a method of measuring rate of
photosynthesis in a green plant.
 Describe how increasing light intensity affects rate
of photosynthesis.
 Describe how increasing concentration of carbon
dioxide affects rate of photosynthesis.
 Describe how increasing temperature affects rate
of photosynthesis.
 Explain why very high temperatures causes rate of
photosynthesis to drop to zero.

19. 4.7 Photosynthesis and Horticulture
Today’s Learning Objectives:
 Explain the term ‘supplementary lighting’.
 Describe how heating and carbon dioxide enrichment
is provided.
 State two effects of supplementary lighting, CO2
enrichment and heating on the harvest of crops.
 What is a disadvantage of providing supplementary
lighting, CO2 enrichment and heating in horticulture.