1. Photosynthesis

2. Lesson Starter (in your jotter)
Write down the equation for photosynthesis
What would happen if one of the RAW MATERIALS for photosynthesis wasn’t present?
What happens to the OXYGEN which is produced during photosynthesis?

3. Today we are going to:
Discuss what happens to the products of photosynthesis
Learn how to test for starch
Carry out the “testing for starch” experiment

4. During photosynthesis..
Plants make OXYGEN and GLUCOSE.
Oxygen leaves the cell
What does the glucose do?

5. The plant converts the glucose into the STORAGE molecule called STARCH

6. Testing for Starch
We can test whether a plant has been PHOTOSYNTHESISING by testing for the presence of STARCH
We use IODINE to test for starch.

7. Before we test the leaf..
Plant cells are WATERPROOF and their CELL WALL makes it difficult for the chemical (IODINE) to get through
We need to PROCESS the leave before we can do a starch test

8. EXPERIMENT Boil the leaf in water for two minutes
(this kills the cell and softens the cell wall)

9. EXPERIMENT
Make sure the Bunsen burner is turned off- ethanol is extremely flamable
Use the heat from the boiling water to heat the leaf in a test tube of ethanol
This removes the chlorophyll- you will notice the ethanol turning green

10. EXPERIMENT The leaf should now be pale in colour
Rinse it in the boiling water
Spread the leaf on the white tile and add a few drops of iodine to it
What do you see happening?

11. Instructions- work in pairs
Set up a tripod stand, Bunsen burner and a beaker filled with 100 mls of water and place the leaf in the water- I will come and light the Bunsen
Boil the leaf in the water for 2 minutes
TURN THE BUNSEN BURNER OFF
Place the leaf in a test tube of ethanol then place the test tube in the beaker of boiling water- you will notice the ethanol starting to go green
Take the leaf out of the ethanol and spread it across the white tile
Add a few drops of iodine
What do you notice?

12. Iodine
In the presence of STARCH, IODINE will turn from yellow/orange to a blue/black colour
Iodine remains yellow
No Starch present
NO PHOTOSYNTHESIS
Iodine turns blue/black
Starch present
PHOTOSYNTHESIS has taken place

13. Complete page 7 in your photosynthesis booklet

14. Complete homework task on page 4 for me to collect in and check tomorrow (Tuesday 1st of September)