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Photosynthesis
Using Light Energy to Make Food
Photosynthesis
Plants use energy to change carbon dioxide and water into glucose and oxygen (waste product)
Who performs Photosynthesis?
Plants and a few bacteriaThese are called autotrophs
Three major events take place in two stages:– Absorption of light energy– Conversion of light energy into
chemical energy (ATP and NADPH)– Storage of energy in the form of
carbohydrates
Where does it happen?
Chloroplasts:– Thylakoids (a single
pancake) Contain chlorophyll
– Grana (stacks) Granum is one stack.
– Stroma (thick fluid that surrounds the grana)
omega.dawsoncollege.qc.ca/ ray/cell/401cell.htm
Light Dependent Reaction– Temperature
independent– Light Reaction
Light Independent Reaction– Calvin-Benson Cycle– Dark Reaction
www.emc.maricopa.edu/faculty/ farabee/BIOBK/BioBookPS.html
Light Reaction
Requires direct light energy Occurs in the thylakoids of chloroplasts 2 steps occur here:
1. Absorption of light by pigments
2. Splitting of water
Electron carriers
Light dependent reaction They gain tons of energy! Cells use electron carriers to transport this energy
to other molecules– Called electron transport (name of process)
2 types in photosynthesis– NADP+
Carriers 2 high energy electrons and hydrogen ions Create NADPH
– ATP
Light Dependent Reaction (depends on light)
Inputs=sun and waterProducts formed
– Oxygen gas-formed by splitting water– Electrons transported to create
NADPH and ATPused in the Calvin-Benson cycle
Calvin Cycle
Occurs in the stroma (filler in chloroplasts)Also called the dark reaction
– Carbon dioxide is the input and the NADPH and ATP from the light reaction
The output is glucose– It is used for food and energy.– Formula for glucose
C6H12O6
The Equation
Sunlight+ 6CO2 + 6H20
---->C6H12O6 + 6 02
Factors that effect the rate of photosynthesis
Temperature Enzymes are important for photosynthesis to work.
– Enzymes work best in certain temperatures.– If the temp is too low or too high, it can decrease it or stop
photosynthesis.
Light intensity– Increase light will increase photosynthesis to a point.
Amount of Carbon Dioxide Amount of water
http://www.brainpop.com/science/cellularlifeandgenetics/photosynthesis/
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