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Energy and Life
 Autotrophs- Organisms that
make their own food using sun’s
energy
 Heterotrophs- Organisms which
obtain energy form foods they
consume
ATP
Adenosine triphosphate
Chemical fuel which
powers cells
Photosynthesis
What happens?
 Plants combine water and carbon dioxide
to make sugar (glucose) and oxygen
 Chlorophyll is needed
 Sunlight provides the energy
 6 CO2 + 6 H2O C6H12O6 + 6 O2
 Water enters the roots and move to the
leaves through xylem
 CO2 enters through small openings in
the leaves called stomata
 Center of leaves have cells with
chloroplasts
 Contain chlorophyll
 Capture light energy
Photosynthesis occurs in
2 main stages
Light-Dependent
Reactions:
1) Sunlight is captured by
chlorophyll
2) Water molecules are
split – produce O2
3) Energy molecules are
made:
a) ATP
b) NADPH
Light-Independent
Reactions
1) Powered by
energy from ATP
and NADPH
2) CO2 comes in
3) Glucose is
produced
These reactions occur in
chloroplasts
 Once sugar is made it can either be:
 Used by plant for energy
 Carried by phloem to roots or stem for
storage
 Oxygen made in the light reactions
leaves the leaf through stomata
Why is Photosynthesis
Important?
 Starts most food chains
 Most autotrophs use photosynthesis to
make food
 Removes CO2 from atmosphere
 Build up of CO2 contributes to Global
Warming