1. Photosynthesis Plants and Oxygen Plant Respiration Parts of Photosynthesis Light Reactions
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Transcript of 1. Photosynthesis Plants and Oxygen Plant Respiration Parts of Photosynthesis Light Reactions
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1. Photosynthesis •Plants and Oxygen•Plant Respiration•Parts of Photosynthesis•Light Reactions
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Photosynthesis
Photosynthesis is essential to all life on earth; both plants and animals depend on it. It is the only biological process that can capture energy that originates in outer space (sunlight) and convert it into chemical compounds (carbohydrates) that every organism uses to power its metabolism.
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Photosynthesis Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere.
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The Plant CellNucleus
Cell Wall
Central Vacuole
Chloroplasts
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Plants and Oxygen Production• Cyanobacteria, like these in
Yellowstone National Park, were the world’s first Oxygen Producers.
• This Oxygen Revolution transformed early earth’s atmosphere.
• It was good for some (allowing for increased efficiency with O2 respiration) but bad for others (in the form of mass extinction of anaerobes)
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StromatolitesStromatolites are special rock-like structures that form in shallow water.
• They are formed by cyanobacteria that use water, carbon dioxide, and sunlight to create their food, and put out oxygen as a by-product.
• The Earliest Evidence of Stromatolites: 3.5 BYA!
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This world map shows Earth’s distribution of photosynthesis as seen via chlorophyll a concentrations. On land, this is evident via terrestrial plants, and in oceanic zones, via phytoplankton.
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Percentage of Earth's Surface Area
Open Ocean
Continental Shelf
Extreme Desert, Rock, Sand, Ice
Tropical Rainforest
Savanna
Cultivated land
Boreal forest
Temperate grassland
Woodland and shrubland
Tundra
Tropical seasonal forest
Temperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Lake and stream
Estuaryu
Algal beds and reefs
Upwelling zones
0 10 20 30 40 50 60 70
Pretty Big!
HUGE!
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Open OceanContinental Shelf
Extreme Desert, Rock, Sand, IceTropical Rainforest
SavannaCultivated land
Boreal forestTemperate grassland
Woodland and shrublandTundra
Tropical seasonal forestTemperate deciduous forestTemperate evergreen forest
Swamp and marshLake and stream
EstuaryuAlgal beds and reefs
Upwelling zones
0 500 1000 1500 2000 2500 3000
Average net primary production (g/m2/yr)
Low Productivity!
High Productivity!
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Open OceanContinental Shelf
Extreme Desert, Rock, Sand, IceTropical Rainforest
SavannaCultivated land
Boreal forestTemperate grassland
Woodland and shrublandTundra
Tropical seasonal forestTemperate deciduous forestTemperate evergreen forest
Swamp and marshLake and stream
EstuaryuAlgal beds and reefs
Upwelling zones
0 5 10 15 20 25 30
Percentage of Earth's net primary production
Way higher than the others!
Oceans and Rainforest are vital to oxygen production on Earth! What will happen if they aren’t protected?
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Photosynthesis/Respiration
Photosynthesis:• Plants use H2O and
carbon dioxide and produce starch and oxygen
H2O + CO2 = Starch/sugar + O2
Respiration• Animals use
starch/sugar and oxygen, and produce H2O and carbon dioxide
Starch/sugar + O2 = H2O + CO2
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Photosynthesis is a multi-step process that requires sunlight, carbon dioxide (low in energy) and water as substrates.
Photosynthesis releases oxygen and produces simple carbohydrate molecules (which are high in energy) that can subsequently be converted dozens of other sugar molecules.
These sugar molecules contain energy and the energized carbon that all living things need to survive.
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Stomata on the underside of a leaf
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An open (left) and closed (right) stoma of a spider plant (Chlorophytum colosum) leaf. When guard cells are turgid, the stoma is open (left).
Stomata on the underside of a leaf
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The Chloroplast• Most of the living world
depends on chloroplasts for its energy!
• Two membranes on outside• Complex membrane structure
on inside
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Photosynthesis Summary
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Photosynthesis SummaryPhotosynthesis takes place in two sequential stages
In the light-independent reactions, the chemical energy harvested during the light-dependent reactions drive the assembly of sugar molecules from carbon dioxide.
In the light-dependent reactions, energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy.
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Absorbed and Reflected Light
Absorbed Light
Reflected Light
Transmitted Light
Plants are green because chlorophyll reflects green light.
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Photosystem
Excited electrons are the key to photosynthesis.
Grannum (stack of thylakoids)
Within the membrane of each thylakoid arecountless clusters of pigments. These pigments are inside Photosystems.
The pigments act as antenna, bouncing photons towards the Primary Electron Receptor
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A photosystem consists of a light-harvesting complex and a reaction center. The first photosystem of photosynthesis is called photosystem 2.
Light harvesting complex
Reaction Center
Photosystem 2
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Pigments in the light-harvesting complex pass light energy (in the form of photons) to two special chlorophyll a molecules in the reaction center.
Chlorophyll a molecules
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The light excites an electron from the chlorophyll a pair, which passes to the primary electron acceptor.
Primary Electron Acceptor
Photosystem 2
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The chlorophyll molecule must get a new electron from somewhere! It’s electron is replaced by the splitting of a water molecule. When a molecule of water is split energy (and oxygen) is released.
OH H
OH H
e-
For every two water molecules that are split, one molecule of O2, the oxygen we breathe, is produced.
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Meanwhile, the excited electron that was raised to the primary electron acceptor is transferred to a mobile carrier protein, that moves it along the electron transfer chain.
As it moves along the electron transfer chain it releases ‘works’ to produce ATP, the currency of energy, that a cell uses. However, as it produces ATP becomes less and less excited.
ATP ATP ATP
Photosystem 2
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ATP ATP ATP
At the end of the Electron Transfer Chain, the electron is no longer excited. It enter Photosystem 1 and is excited again by the photons boosting it back into it’s high energy state.
e-
Photosystem 1 Photosystem 2
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ATP ATP ATP
The re-excited electron is again transferred to a mobile carrier protein, that moves it along the electron transfer chain, however this time it is combined with another electron, one proton, and a molecule of NADP+ to create a molecule of NADPH.
NADP+
H
NADPH
Photosystem 1
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Active Transport: Proton pumps
The ATP released during the ETC transfer is used to drive proton pumps which sets up a concentration gradient of high H+ inside the thylakoid (lumen) and a low H+ outside the thylakoid (stroma)
H
H
Inside of Thylakoid
Outside of Thylakoid
ATP
ATP
H
HHH
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ATPase Activity
H
Inside of Thylakoid
Outside of Thylakoid
ADP
Protons (H+) flow down concentration gradient through ATPase, an enzyme that synthesizes ATP.
PH
HHH
HHH
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Light Reactions• Light boosts electrons in Photosystem II, high energy
electrons passed along chain of carriers • Electrons replaced by splitting water• Passage of electrons down chain releases energy
used to fuel proton pumps to generate ATP• Chain ends in Photosystem I, electron energy
boosted again, passed on to NADPH• ATP, NADPH (fuel) produced by light reactions
provide energy to power Calvin Cycle (making sugar)
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