1. Photosynthesis

2. What is photosynthesis?
Write a sentence or two to describe what photosynthesis is. Use the
keywords: light energy, carbon dioxide, water, oxygen, chlorophyll,
chemical energy, photosynthesis.
Plants use photosynthesis to convert carbon dioxide and water,
in the presence of chlorophyll and light energy, to make glucose and
oxygen. Photosynthesis is important in converting light energy to
chemical energy.

3. carbon dioxide + water glucose + oxygen 6CO2 6H20 C6H12O6 602 Photosynthesis is an important process because it converts light energy to chemical energy, which is stored in glucose. The chemical energy is released when glucose is broken down during respiration.
light
chlorophyll

4. Cross-section of a leaf

5. upper epidermis
Palisade cell
vascular bundle
spongy mesophyll
layer
air space
guard cells
stoma

7. Exam question
(c) The leaves produce glucose by photosynthesis. (i) Write the word equation for photosynthesis (2) (ii) Describe how the structure of the leaf is adapted to help obtain the gas required for photosynthesis (2)

8. Exam question
(c) The leaves produce glucose by photosynthesis. (i) Write the word equation for photosynthesis. carbon dioxide + water  glucose + oxygen (2) (ii) Describe how the structure of the leaf is adapted to help obtain the gas required for photosynthesis. thin; large surface area; stomata; air spaces / spongy (mesophyll); (2)

9. How can we test that photosynthesis has occurred in plants?
What is the evidence for photosynthesis?
How can we test for starch?

10. How can we test that photosynthesis is occurring in plants?
Presence/ absence of light
oxygen given off
How can we test that photosynthesis is occurring in plants?
Presence/
absence
of CO2
starch produced
Presence / absence of chlorophyll

11. Pondweed experiments

12. Investigating the requirements for starch production
Why destarch the plants before setting up each investigation?
Light
Set up and leave in sunlight for 24 hours

13. 2. Carbon dioxide light Spot the difference!
soda lime
Spot the difference!
What’s the purpose of adding soda lime?

14. 2. Carbon dioxide

15. 3. Chlorophyll
Predict the results of the starch test.
Take a variegated plant which has been under bright light for 24hours and remove one of the leaves.
Make a sketch of the leaf showing approximately where the green and non green areas are.

16. Testing Leaves for Starch
Dunk the leaf in a 90oC water bath using forceps until it is soft (2 minutes).
Transfer leaf to a boiling tube of ethanol and place in 90oC water bath until the leaf turns white (5 minutes).
Wash the leaf in water.
Place the leaf on a Petri dish and flood with iodine solution.

17. Starch Test (diagrams)
Results
Write up results and include diagrams.
Condition
Treatment
Starch Test (diagrams)
Before
After
Light
Carbon dioxide
Chlorophyll

18. Conclusions What do your results tell you about photosynthesis and …
a. light?
b. carbon dioxide?
c. chlorophyll?
What was the control for each experiment?
It is difficult to set up an experiment to prove that water is needed for photosynthesis. Explain why it is difficult.

19. Light and starch production
Take a finely sliced piece of potato and place on a glass slide
add two drops of iodine solution and place a coverslip on top
view under the microscope.
What can you see?
summary