4.1 Chemical Energy & ATP 4.2 Overview of Photosynthesis 4.3 Photosynthesis in Detail CELL ENERGY.
Photosynthesis Ch. 10. Photosynthesis has two stages: Light reactions energy from the sun is...
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Transcript of Photosynthesis Ch. 10. Photosynthesis has two stages: Light reactions energy from the sun is...
Photosynthesis
Ch. 10
Photosynthesis has two stages:
Light reactionsenergy from the sun is absorbed and converted into
ATPWater molecules are split and NADP+ picks up the free
hydrogen and electrons to make NADPHTakes place in the thylakoid membrane system
Calvin CycleATP gives energy to sites where glucose (C6H12O6) is
formedNADPH delivers hydrogenCO2 donates carbon and oxygenTakes place in the stroma
Photoautotrophs can only harness the wavelengths between 400 and 750 nanometers. This is also the range of visible light.
Pigments are the “molecular bridge” Absorb wavelengths of light and organisms use them
Chlorophylls are the main pigments of photosynthesis Absorb all wavelengths except very little of the green
and yellow-green ones
How do pigments work?
Each pigment has a light-catching set of atoms Electrons of a pigment’s light-catching area absorb
photons (packets of light energy) Electrons move to higher energy level, then back
down releasing energy The energy is passed on to “neighbors” called a
photosystem Energy is passed on and on until it reaches the
“reaction center”
SUMMARY 3 Things happen in light reactions
Pigments of photosystems absorb photon energy and give up excited electrons
Transfers of electrons and hydrogen through electron transport systems leads to ATP and NADPH formation
Pigments that gave up electrons get electron replacements
Noncyclic Photophosphorylation
Cyclic Photophosphorylation
Calvin Cycle
“Synthesis” part of photosynthesis ATP provides energy for the reactions NADPH supplies the hydrogen and electrons CO2 provides the carbon and oxygen
RESULT: sugar
C4 Plants
Modified for DRY environments Thrive in hot/sunny environments
Modified anatomy that allows them to minimize excess water loss and maximize sugar production
Pump CO2 deep into leaf in bundle-sheath cells before going though Calvin Cycle
This way, oxygen doesn't inhibit the Calvin Cycle Get away with having smaller stomata, thus losing less
water
CAM Plants
Also adapted to dry conditions Keep stomates closed during the day and open at night This is the reverse of how most plants behave Fixes CO2 at night and stores materials to use for
photosynthesis the next day (when stomata close)