Bioenergetics

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Bioenergetics Lecture 5
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Lecture 5

• Detail of Light Reactions
• Detail of Calvin Cycle
• Photorespiration and C4 and CAM plants
• Greenhouse Effect
• Ozone Depletion

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Light is a type of Energy
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A variety of pigments are involved in absorbing
light of different wavelengths
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Light also behaves as discrete packages of
energy called photons
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You can see this phenomena in the vitro
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Within the thylakoid membranes, many pigment
molecules are grouped with associated proteins
into an antenna assembly, but only one
chlorophyll a molecule acts as the reaction center
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Light Reactions
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Electron transport chain generates ATP, NADPH and
O2
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Chemiosmosis powers ATP synthesis in the light
reactions
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The Calvin Cycle converts CO2 to sugar
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Photosynthesis Review
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Photorespiration
Plants that only use the Calvin Cycle to fix
carbon are know as C3 plants. Under bright, hot,
and/or dry conditions these plants can have a
problem due to photorespiration
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C4 Plants
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CAM Plants
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Human activity causes global warming
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Mario Molina was one of the first scientist to
write about the depletion of the ozone He
proposed a model for how the earths protective
ozone layer was being depleted Predicted many
long-term environmental and economic costs for
not dealing with the problem
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Ozone Depletion
In the upper atmosphere O2 is converted into O3
(ozone) by high energy solar radiation. The
ozone layer protects the earth from UV radiation.
UV radiation is damaging to life.
Chlorofluorocarbons are human made chemicals that
were used as refrigerants and propellants. These
CFCs deplete ozone and result in increased UV
radiation reaching the earths surface. CFC
production has now been banned in developed
countries but it will take atleast 50 years for
the ozone layer to begin to recover.