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Photosynthesis, Photosynthesis 2, photosynthesis 3, photosynthesis 4,…
Photosynthesis
The requirenents for photosynthesis
Chlorophyll
--> absorbs the energy from light
--> is the chloroplasts of the leaf
Carbon dioxide
--> diffuses into the leaves from the air
Light
--> provides energy for the proces
Water
--> absorbed by the plants roots from the soil
De-starching
We must make sure that the leaves have no starch
Leave the plant in the dark for 48 hours
Balance chemical equation
6CO2 + 6H2O → C6H12O6 + 6O2
Light energy absorbed by chlorophyll
Chemical energy to drive the reactions that from carbohydrates from water and carbon dioxide
Energy used to split water into
hydrogen ions
and oxygen
Reduce carbon dioxide to carbohydrates
Provides energy for plants and for other organisms
Feed on plants directly or incirectly
Plant may use oxygen:
Own respiration
Diffuse out into the atmosphere
Tests
Leaf for starch
1) Sumerge a leaf in boiling water for one minute (easier to extract the chlorophyll)
2) Turn off the Bunsen burners
3) Put the leaf into a test-tube --> chlorophyll extracted by dissolving into the ethanol
4) Stan the test-tube down hot water for 10 minutes
5) Wash the leaf in cold water (removes the ethanol and rehydrates the leaf)
6) Spread the leaf out on a flat/white surface and put some drops of iodine solution
7) leaf goes :
blue/black starch is present
red/brown no starch
Showing that carbon dioxide is needed for photosynthesis
1) Take a de-starched plant, Enclose it in a plastic bag with a chemical that absorbs carbon dioxide (ex: soda lime)
2) Leave the plant in the light for a few hours. Test a leaf for starch.
The leaf should show a negative result for the starch test- Deprived of carbon dioxide the lead is unable to photosynthesise and make starch.
Showing that light is needed for photosynthesis
1) Take a de-starched plant. Cover part of the leaf with some aluminium foil to prevent light getting through.
2) Leave the plant in the light for a few hours
3) Test the leaf for starch.
The parts of the leaf that were left uncovered go blue/black
The parts of the leaf that were covered did not receive light and could not carry out photosynthesis --> could not make starch
Showing that chlorophyll is needed for photosynthesis
1) Take a de-starched, variegated (white parts in a leaf because there is no chlorophyll there) plant.
2) Place it in sunlight for six hours
Only green parts of the leaf goes blue/black (they have chlorophyll to make starch)
3) Test the variegated leaf for starch
White parts contain no chlorophyll --> photosynthesis occurs there
What is it?
Green plants use light energy to convert carbon dioxide and water into simple sugars
Plants make carbohydrates from raw materials using light energy
carbon dioxide + water
light and chlorophyll
glucose + oxygen
