c astlehead h igh s chool photosynthesis intermediate 2 how plants make food
TRANSCRIPT
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What is photosynthesis?What is photosynthesis?
The word The word photophoto means means light and light and synthesissynthesis means to build upmeans to build up
Photosynthesis is the Photosynthesis is the process whereby green process whereby green plants make glucoseplants make glucose
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What does the plant need ?What does the plant need ?
For photosynthesis to take For photosynthesis to take place a plant needs place a plant needs
Carbon dioxide Carbon dioxide from the airfrom the air
LightLight from the sun from the sun
Water Water from the soilfrom the soil
ChlorophyllChlorophyll from the from the leaves leaves
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Testing for photosynthesisTesting for photosynthesis
We can check for evidence of We can check for evidence of photosynthesis by testing a leaf for starch.photosynthesis by testing a leaf for starch.
1.1. Boil the leaf in water (bursts cells)Boil the leaf in water (bursts cells)
2.2. Boil the leaf in alcohol (removes chlorophyll)Boil the leaf in alcohol (removes chlorophyll)
3.3. Dip leaf in hot water (softens the leaf)Dip leaf in hot water (softens the leaf)
4.4. Put leaf in iodine solution (turns blue black if Put leaf in iodine solution (turns blue black if starch is present)starch is present)
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Test for Starch
Boil for 1 Minute Warm in Ethanol
Testing a leaf for StarchTesting a leaf for StarchWash in Water
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Testing your knowledgeTesting your knowledge A variegated leaf is covered with a strip of A variegated leaf is covered with a strip of
metal foil then the leaf is tested for starch. metal foil then the leaf is tested for starch. Which diagram shows the correct result.Which diagram shows the correct result.
Metal foil
Blue Black Starch present
Orange No Starch present
A B C D
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Word Equation for Word Equation for PhotosynthesisPhotosynthesis
CarbonDioxide
+ Water Glucose + Oxygen
CO2 H2O C6H12O6 O2
Light energy
Raw Materials Products
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Stages of PhotosynthesisStages of Photosynthesis
1st Stage - 1st Stage - PHOTOLYSISPHOTOLYSIS
Light energy
Absorbed by Chlorophyll
WATER
ADP + Pi
ATP
HYDROGEN + OXYGEN
Only HYDROGEN and ATP go on to the second stage
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22ndnd Stage Carbon Fixation Stage Carbon Fixation
HYDROGEN
ATP
ADP + Pi
GLUCOSE
Starch
Cellulose
+ CARBON DIOXIDE (from the air)
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Glucose
What happens to the glucose?What happens to the glucose?
Cellulose made up of parallel chains of glucose to form tough fibres used to make cell walls
For energyin respiration
Starch made up of coiled chains of glucose to form starch grains.
Can be converted back when glucose is needed byplant.
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Limiting FactorsLimiting Factors Carbon Dioxide Concentration - Carbon Dioxide Concentration - Less Carbon
Dioxide means less glucose can be made.
Light Intensity - More light means more energy
Temperature -Temperature - Warmth increases the rate that enzymes work, however, high temperature denatures enzymes. Low temperatures slow reactions.
If any of these are in short supply, they cut down or LIMIT the rate of photosynthesis.
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Rate of PhotosynthesisRate of Photosynthesis
If we move If we move the lamp the lamp back and back and forwards we forwards we can change can change the light the light intensityintensity
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Light IntensityLight IntensityR
ate
of P
hoto
synt
hesi
s
Light Intensity
CO2 readily availableand warmth
If light is increased photosynthesis will increase up to a certain point.After this something else becomes the limiting factor e.g. CO2
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Limiting FactorsLimiting Factors
Level of CO2
What is the limiting factor at point X?
What is the limiting factor at point Y?X
Y
Rat
e of
Pho
tosy
nthe
sis
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More to do!More to do! Go to Go to http://lgfl.skoool.co.uk/keystage3.aspx?id=63http://lgfl.skoool.co.uk/keystage3.aspx?id=63
and do lesson numbersand do lesson numbers
49. Photosynthesis49. Photosynthesis50. The Role of the Leaf in Photosynthesis50. The Role of the Leaf in Photosynthesis51. Rate of Photosynthesis51. Rate of Photosynthesis52. Testing a Leaf for Starch52. Testing a Leaf for Starch53. Experiments to see if Chlorophyll and 53. Experiments to see if Chlorophyll and
Light are Needed to Make StarchLight are Needed to Make Starch54. The Uses of Glucose 54. The Uses of Glucose