Download KA 7 Summary sheet

Biology: Key Area 7
Summary Sheet
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The overall word equation for photosynthesis is:
Carbon dioxide + water
Raw materials
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Light energy
Chlorophyll
glucose + oxygen
Products
Photosynthesis is a two stage process.
The first stage of photosynthesis is called the Light Reaction and
depends on light energy.
During the Light Reaction, light energy from the sun is trapped by
chlorophyll (the green pigment in chloroplasts) and is converted
into chemical energy in the form of ATP.
ATP is used to split water into hydrogen and oxygen.
Excess oxygen diffuses out of the cell.
Hydrogen attaches to hydrogen acceptor molecules and is carried
to stage 2.
ATP made in the Light Reaction is also used in stage 2.
The second stage of photosynthesis is called carbon fixation.
The second stage is called carbon fixation and is a series of
enzyme controlled reactions.
Hydrogen and ATP produced by the Light Reaction (stage 1) are
used.
ATP is used as the energy source.
The hydrogen combines with carbon dioxide from the atmosphere
to produce a sugar called glucose.
The chemical energy in the glucose is available to use in a process
called respiration.
The glucose can also be converted into a starch or cellulose.
Starch is a large and insoluble storage carbohydrate.
Cellulose is a structural carbohydrate that is used to build the
plant cell wall.
Limiting factors of photosynthesis are carbon dioxide
concentration, light intensity and temperature.
If in short supply, limiting factors limit the rate of photosynthesis
and therefore, plant growth.
To measure the rate of photosynthesis in a green plant, count the
number of oxygen bubbles released per unit of time.