9/13/2015 1 PHOTOSYNTHESIS: THE LIGHT REACTIONS ECOSYSTEM Photosynthesis Organic molecules Cellular respiration in mitochondria CO 2 +H 2 O +O 2
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PHOTOSYNTHESIS:THE LIGHT REACTIONS
ECOSYSTEM
Photosynthesis
Organicmolecules
Cellularrespiration inmitochondria
CO2 + H2O + O2
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PHOTOAUTOTROPHSThe producers of the biosphere
AUTOTROPH means
“self feeder”
20% of the world’s oxygen is produced
in rain forests
PHOTOAUTOTROPHSNot just plants!
Giant kelp (a eukaryote) can grow up
to 2ft each day
Marine alga produce 70‐80% of the world’s oxygen
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PHOTOAUTOTROPHSNot just plants and protists
Cyanobacteria are single celled prokaryotes that are
also photoautotrophs
CHLOROPLASTSUse sunlight to convert water and CO2 to glucose
Collection of enzymes and pigments
Prokaryotes (like cyanobacteria) have similar parts that are NOTbound by membranes.
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LEAVESAre made of millions of plant cells filled with chloroplasts
Leaves have many stoma (stomata = singlular) which means “mouth”
Stoma allow CO2 to enter the leaf and O2 to exit
MESOPHYLL CELLSEach contain 30 – 40 chloroplasts. Important for photosynthesis!
Leaf Cross Section
Leaf
Vein transports materials through plant
Mesophyll Cell
CO2O2
Stoma
Chloroplast
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MESOPHYLL CELLSPlant cells that contain 30‐40 chloroplasts
Mesophyll Cell
Chloroplast
Inner and outermembranes
CHLOROPLASTSPhotosynthetic machinery covered by an inner and outer membrane
Note: prokaryotes can have similar structures but they are NOT bound by membranes
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CHLOROPLASTSPhotosynthetic machinery covered by an inner and outer membrane
Chloroplast
Granum
Thylakoid
Thylakoid spaceStroma
THYLAKOIDS:membrane that forms interconnected sacs where light energy is converted to chemical energy
THYLAKOID SPACE:Space on the inside of the thylakoid membranes where H+ ions are pumped to create a gradient
Lightenergy
Carbon dioxide Water
Photosynthesis
Sugar 6 O26 CO2 6 H2O
PHOTOSYNTHESISUse light energy to convert CO2 and water to sugar and O2
Another REDOX process! Yay! Our FAVORITE!
Thylakoid
Thylakoid space
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SOLAR ENERGYSolar energy is a type of electromagnetic energy (radiation) from the sun
PIGMENTS HARVEST SOLAR ENERGYPigments are molecules that absorb light
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PIGMENTS IN CHLOROPHLASTSChlorophyll a, chlorophyll b, carotenoids
PIGMENTS ABSORB LIGHT ENERGYEnergy from the sun “excites” electrons in pigments and increases their potential energy
Excited state
HeatPhotonof light
Chlorophyllmolecule
Ground state
Photon(fluorescence)
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Light
STROMAPrimary electronacceptor
THYLAKOIDSPACE Transfer
of energyPair of
chlorophyll amolecules
Pigmentmolecules
Th
ylak
oid
mem
bra
ne
PHOTOSYSTEM II
Pigments are organized into photosystems that capture and convert solar energy
PHOTOSYSTEM IIIn the thylakoid membrane of a chloroplast of a mesophyll plant cell and we are passing energy from pigment to pigment
Light
THYLAKOIDSPACE
Th
ylak
oid
m
emb
ran
e
An electron is transferred at the end of the energy chain
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Light
H2O½ o2 + 2H+
Electrontransport chain
H+
H+
H+H+
Photosystem II
PHOTOSYSTEM IIUse light energy to transport electrons from water molecules
PHOTOSYSTEM IExcite electrons further, reduce NADP+ to NADPH
Electron transport chain
NADP+NADPH
H+
H+
H+
H+H+
H+
H+
H+
Light
H+
H+
H+
H+
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Light
PhotosystemII
H2OO2 + 2 H+1
21
Electrontransport chain
H+
H+
H+
H+
H+
H+
H+
H+
LightPhotosystem
I
H+
H+H+
H+
H+NADP+
NADPH
To CalvinCycle
H+
H+
THYLAKOID SPACE
STROMA
Thylakoid membrane
H+
ATP synthase
H+
H+
H+
H+
H+
H+H+
H+
H+ H+
H+
P ATPADP +
THE LIGHT REACTIONSTale place on the membrane of the thylakoid
PHOTOSYSTEM II• Electrons are excited and transferred to transport chain using light
energy• Enzymes split water, replenish electrons and build a H+ gradient• Oxygen is formed and released
PHOTOSYSTEM II• Electrons are excited and transferred to NADP+ using light energy• NADP+ is reduced to NADPH for use in the Calvin Cycle• ATP synthase converts ADP + P used in the Calvin Cycle to ATP to be
used again by the Calvin Cycle
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Light
PhotosystemII
H2OO2 + 2 H+1
21
Electrontransport chain
H+
H+
H+
H+
H+
H+
H+
H+
LightPhotosystem
I
H+
H+H+
H+
H+NADP+
NADPH
To CalvinCycle
H+
H+
THYLAKOID SPACE
STROMA
Thylakoid membrane
H+
ATP synthase
H+
H+
H+
H+
H+
H+H+
H+
H+ H+
H+
P ATPADP +
REQUIRED VIDEOSThis core concepts of this material is fair game for our next check‐in
“The simple story of photosynthesis and food”See link on the course website
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