Opportunities multiply as they are seized'

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"Opportunities multiply as they are seized."
Sun Tzu
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Photosynthesis
Photosynthesis capture light energy from the sun
and convert it into chemical energy stored in
organic molecules 6CO2 6H2O light ? C6H12O6
6O2 Photoautotrophs C CO2
Photoheterotrophs C organic carbon
Foundation of energy for most ecosystems Source
of oxygen
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Anoxygenic dont form oxygen as a product of
photosynthesis Oxygenic (our focus) form oxygen
as a product of photosynthesis (ex. Cyanobacteria
and plants)
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Solar energy and light
The electromagnetic spectrum
Pigment molecules absorb some wavelengths of
light reflect others Chlorophyll a green
photosynthetic pigment associated with membranes
and chloroplasts
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When a molecule absorbs a photon, one of that
molecules electrons is elevated to an orbital
with more potential energy
Excited electrons are unstable they drop to
their ground state in a billionth of a second
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• In the thylakoid membrane, chlorophyll is
  organized along with proteins into photosystems

A photosystem acts like a light-gathering
antenna complex consisting of a few hundred
chlorophyll
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Light dependent reaction of P.S.
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Potential energy
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Chemiosmosis
At the end of the light dependent Rx we end up
with ATP and NADPH
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Fig. 10.4
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The Calvin cycle uses ATP and NADPH to convert
CO2 into sugar
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Each CO2 molecule is attached to a five-carbon
sugar, ribulose bisphosphate (RuBP) by rubisco
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The six-carbon intermediate splits in half to
form two molecules of 3-phosphoglycerate per CO2
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Each 3-phosphoglycerate receives another
phosphate group from ATP to form 1,3
bisphosphoglycerate
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A pair of electrons from NADPH reduces each 1,3
bisphosphoglycerate to G3P
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If our goal was to produce one G3P net, we would
start with 3 CO2 (3C) and 3 RuBP (15C) We would
have six molecules of G3P (18C) 1 G3P (3C) is a
net gain of carbohydrate can exit the cycle
The other 5 G3P (15C) must remain in the cycle
to regenerate three RuBP These 5 G3P molecules
are rearranged to form 3 RuBP molecules
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