8.2: Photosynthesis
involves the use of light energy
to change water (H20) &
carbon dioxide (CO2)
into oxygen (O2) &
glucose (C6H12O6 )
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Plants!
Photosynthesis mainly occurs in the
leaves.
chloroplast
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Photosynthesis requires
pigments.
Different pigments absorb
different wavelengths of light.
Chlorophyll is the primary lightabsorbing pigment.
Plants are green because the
green wavelength of light is
reflected, not absorbed.
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Plants also contain other pigments
called carotenoids.
These pigments are red, orange or
yellow and give plants their fall
colors.
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Chlorophyll is found inside a
chloroplast – the organelle where
photosynthesis takes place.
Outer Membrane
Inner Membrane
Thylakoid
Thylakoids contain clusters of chlorophyll
molecules.
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The Photosynthesis Equation
In symbols:
6 CO2 + 6 H2O  C6H12O6 + 6 O2
In words:
Glucose!
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Parts of
Photosynthesis
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Photosynthesis Begins!
Stage 1: Pigments absorbs light
energy & excite electrons of
chlorophyll
Electrons are passed to the electron
transport chain.
Lost electrons are replaced from the
splitting of water.
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Stage 2: Light-Dependent
Reactions (Light Reactions)
Produces cellular energy from
light energy in the form of
ATP and NADPH.
SUN
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Occurs across the thylakoid
membranes.
Uses light energy.
Produce oxygen from water.
Produces ATP & NADPH.
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Light-Dependent Summary
Reactants:
• light energy
• water
Energy Products:
• ATP
• NADPH
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Light Dependent Reaction
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Stage 3: Light - Independent
Reactions (Dark Reactions )
Uses energy (ATP and NADPH)
from light reactions to make
sugar (glucose).
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ATP & NADPH from light
reactions used as energy
Atmospheric C02 is used to
make sugars (glucose)
Sugar (glucose) is made during
the Calvin cycle.
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Light-Independent Summary
Reactants:
• CO2
• ATP & NADPH
Energy Products:
• Glucose (C6H12O6)
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Photosynthesis Overview
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Factors Affecting the Rate of
Photosynthesis
Amount of available
water & carbon
dioxide
Temperature
Amount of available
light energy
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