Photosynthesis ppt by Lalit Kumar
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Transcript of Photosynthesis ppt by Lalit Kumar
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PHOTOSYNTHESIPHOTOSYNTHESISS
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PhotosynthesisPhotosynthesis• AnabolicAnabolic (small molecules combined) (small molecules combined)• EndergonicEndergonic (stores energy) (stores energy)• Carbon dioxide (COCarbon dioxide (CO22)) requiring requiring
process that uses process that uses light energy light energy (photons)(photons) and and water (Hwater (H22O)O) to produce to produce organic macromolecules (glucose).organic macromolecules (glucose).
6CO2 + 6H2O C6H12O6 + 6O2
glucoseglucose
SUNphotonsphotons
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Question:Question:
Where does Where does photosynthesiphotosynthesis take place?s take place?
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PlantsPlants• Autotrophs Autotrophs – produce their own – produce their own
food food (glucose)(glucose)• Process called Process called photosynthesisphotosynthesis• Mainly occurs in the Mainly occurs in the leaves:leaves:
a.a.stoma - poresstoma - poresb.b.mesophyll cellsmesophyll cells
StomaMesophyllCell
Chloroplast
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Stomata (stoma)Stomata (stoma)PoresPores in a plant’s cuticle in a plant’s cuticle
through which through which water vaporwater vapor and and gasesgases (CO(CO22 & O & O22)) are are exchanged between the plant exchanged between the plant and the atmosphere.and the atmosphere.
Guard CellGuard CellCarbon Dioxide (CO2)
Oxygen (O2)
Found on the underside of Found on the underside of leavesleaves
StomStomaa
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Mesophyll Cell of LeafMesophyll Cell of Leaf
Cell WallNucleusNucleus
Chloroplast
Central Vacuole
Photosynthesis occurs in these Photosynthesis occurs in these cells!cells!
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ChloroplastChloroplastOrganelleOrganelle where
photosynthesisphotosynthesis takes place.
GranumThylakoidStroma
Outer MembraneInner Membrane
Thylakoid stacks are connected Thylakoid stacks are connected togethertogether
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ThylakoidThylakoid
Thylakoid Membrane
Thylakoid SpaceGranum
Grana make up the inner Grana make up the inner membranemembrane
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Question:Question:
Why are Why are plants plants green?green?
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Chlorophyll MoleculesChlorophyll Molecules• Located in the Located in the thylakoid membranesthylakoid membranes• Chlorophyll have Chlorophyll have MgMg++ in the center in the center• Chlorophyll pigments Chlorophyll pigments harvest energy harvest energy
(photons)(photons) by absorbing certain by absorbing certain wavelengths wavelengths (blue-420 nm and red-(blue-420 nm and red-660 nm660 nm are most important) are most important)
• Plants are Plants are greengreen because the because the green green wavelength is reflectedwavelength is reflected, not absorbed, not absorbed.
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Wavelength of Light (nm)Wavelength of Light (nm)
400 500 600 700
Short wave Long wave(more energy) (less energy)
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Absorption of Light by Absorption of Light by ChlorophyllChlorophyll
wavelengthwavelength
Absorption
violet blue green yellow orange red
Chlorophyll absorbs blue-violet & red Chlorophyll absorbs blue-violet & red light bestlight best
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Question:Question:
During the fall, During the fall, what causes what causes the leaves to the leaves to
change colors?change colors?
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Fall ColorsFall Colors• In addition to the chlorophyll In addition to the chlorophyll
pigments, there are pigments, there are other other pigmentspigments present present
• During the fall, the During the fall, the green green chlorophyll pigments are greatly chlorophyll pigments are greatly reducedreduced revealing the other revealing the other pigmentspigments
• CarotenoidsCarotenoids are pigments that are pigments that are either are either redred, , orangeorange, or , or yellowyellow
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Redox ReactionRedox ReactionThe The transfertransfer of one or more of one or more
electronselectrons from one reactant from one reactant to anotherto another
Two types:Two types:1.1. Oxidation is the Oxidation is the lossloss of e of e--
2.2. Reduction is the Reduction is the gaingain of of ee--
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Oxidation ReactionOxidation ReactionThe The loss of electronsloss of electrons from a from a
substance or the substance or the gain of gain of oxygen.oxygen.
glucoseglucose6CO2 + 6H2O C6H12O6 + 6O2
OxidationOxidation
Carbon Carbon dioxidedioxide WaterWater OxygenOxygen
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Reduction ReactionReduction ReactionThe The gain of electronsgain of electrons to a to a
substance or the substance or the loss of loss of oxygen.oxygen.
glucoseglucose6CO2 + 6H2O C6H12O6 + 6O2
ReductionReduction
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Question:Question:
Why do Why do cells use cells use
for for energy?energy?
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Energy for Life on EarthEnergy for Life on Earth•Sunlight is the ULTIMATE
energy for all life on Earth•Plants store energy in the
chemical bonds of sugars•Chemical energy is
released as ATP during cellular respiration
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Structure of ATPStructure of ATP• ATP stands for adenosine
triphosphate• It is composed of the nitrogen
base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups
• The LAST phosphate group is bonded with a HIGH ENERGY chemical bond
• This bond can be BROKEN to release ENERGY for CELLS to use
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Removing a Phosphate from Removing a Phosphate from ATPATP
Breaking the LAST PHOSPHATE bond from ATP, will ---– Release ENERGY for cells to use– Form ADP– Produce a FREE PHOSPHATE
GROUP
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High Energy Phosphate High Energy Phosphate BondBond
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FREE PHOSPHATE can be re-FREE PHOSPHATE can be re-attached to ADP reforming ATPattached to ADP reforming ATPProcess called Process called PhosphorylationPhosphorylation
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PhosphorylationPhosphorylation
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Parts of Parts of PhotosynthesisPhotosynthesis
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Two Parts of Two Parts of PhotosynthesisPhotosynthesis
Two reactions make up Two reactions make up photosynthesis:photosynthesis:
1.1.Light Reaction or Light Light Reaction or Light Dependent ReactionDependent Reaction - - Produces energy from solar Produces energy from solar power (photons) in the form power (photons) in the form of ATP and NADPH.of ATP and NADPH.
SUNSUN
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Two Parts of Two Parts of PhotosynthesisPhotosynthesis
2. 2. Calvin Cycle or Light Calvin Cycle or Light Independent Independent ReactionReaction
• Also called Also called Carbon FixationCarbon Fixation or or CC33 Fixation Fixation
• Uses energy (Uses energy (ATP and ATP and NADPHNADPH) from light reaction ) from light reaction to make sugar to make sugar (glucose).(glucose).
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Light Reaction (Electron Light Reaction (Electron Flow)Flow)
• Occurs in the Occurs in the Thylakoid Thylakoid membranesmembranes
• During the During the light reactionlight reaction, , there are there are twotwo possible routes possible routes for electron flow:for electron flow:A.A. Cyclic Electron FlowCyclic Electron FlowB.B. Noncyclic Electron FlowNoncyclic Electron Flow
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Cyclic Electron FlowCyclic Electron Flow• Occurs in the Occurs in the thylakoidthylakoid membrane. membrane.• Uses Uses Photosystem I onlyPhotosystem I only• P700P700 reaction center- chlorophyll reaction center- chlorophyll
a a • Uses Electron Transport Chain Uses Electron Transport Chain
(ETC)(ETC)• Generates Generates ATP onlyATP only
ADP + ADP + ATP ATPP
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Cyclic Electron FlowCyclic Electron Flow
P700
PrimaryElectronAcceptor
e-
e-
e-
e-
ATPATPproducedby ETC
Photosystem I
AccessoryPigments
SUN
Photons
Pigments absorb light energy & excite Pigments absorb light energy & excite e- of Chlorophyll a to produce ATP e- of Chlorophyll a to produce ATP
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Noncyclic Electron FlowNoncyclic Electron Flow• Occurs in the Occurs in the thylakoidthylakoid membrane membrane• Uses Uses Photosystem II Photosystem II and and
Photosystem IPhotosystem I• P680 P680 reaction center reaction center (PSII)(PSII) - -
chlorophyll achlorophyll a• P700P700 reaction center reaction center (PS I)(PS I) - -
chlorophyll achlorophyll a• Uses Electron Transport Chain Uses Electron Transport Chain
(ETC)(ETC)• Generates Generates OO22, ATP and NADPH, ATP and NADPH
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Noncyclic Electron FlowNoncyclic Electron Flow
P700
Photosystem IP680
Photosystem II
PrimaryElectronAcceptor
PrimaryElectronAcceptor
ETC
EnzymeReaction
H2O
1/2O1/2O22 + 2H+
ATPATP
NADPHNADPHPhoton
2e-
2e-
2e-
2e-
2e-
SUN
Photon
HH22O is split in PSII & ATP is made, while the energy carrier O is split in PSII & ATP is made, while the energy carrier NADPH is made in PSINADPH is made in PSI
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Noncyclic Electron FlowNoncyclic Electron Flow
• ADP +ADP + ATPATP• NADPNADP++ + H + H NADPHNADPH• OxygenOxygen comes from the comes from the
splitting of Hsplitting of H22O, not COO, not CO22
HH22O O 1/2 O 1/2 O22 + 2H + 2H++
PP
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ChemiosmosisChemiosmosis• Powers Powers ATP synthesisATP synthesis• Takes place across the thylakoid Takes place across the thylakoid
membranemembrane• Uses Uses ETCETC and and ATP synthase ATP synthase
(enzyme)(enzyme)• H+H+ move down their move down their
concentration gradient through concentration gradient through channels of ATP synthasechannels of ATP synthase forming forming ATP from ADPATP from ADP
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ChemiosmosisChemiosmosisH+ H+
ATP Synthase
H+ H+ H+ H+
H+ H+ high Hhigh H++
concentrationconcentration
H+ADP + P ATP
PS II PS IE
TC
low Hlow H++
concentrationconcentration
H+ThylakoidThylakoidSpaceSpace
ThylakoidThylakoid
SUN (Proton Pumping)
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Calvin CycleCalvin Cycle• Carbon Fixation Carbon Fixation (light independent (light independent
reaction)reaction)• CC33 plants (80% of plants on earth) plants (80% of plants on earth)• Occurs in the Occurs in the stromastroma• Uses Uses ATP and NADPHATP and NADPH from light from light
reaction as energyreaction as energy• Uses Uses COCO22• To produce To produce glucoseglucose: it takes : it takes 6 6
turns and uses 18 ATP and 12 turns and uses 18 ATP and 12 NADPH. NADPH.
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ChloroplastChloroplast
GranumThylakoidSTROMA– where Calvin Cycle occurs
Outer MembraneInner Membrane
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Calvin Cycle (CCalvin Cycle (C33 fixation) fixation)
6CO2
6C-C-C-C-C-C6C-C-C 6C-C-C
6C-C-C-C-C
12PGA
RuBP
12G3P
(unstable)
6NADPH 6NADPH
6ATP 6ATP
6ATP
C-C-C-C-C-CGlucose
(6C)(36C)
(36C)
(36C)
(30C)
(30C)
(6C)
6C-C-C 6C-C-C
C3glucose
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Calvin CycleCalvin CycleRemember: CRemember: C33 = Calvin Cycle = Calvin Cycle
C3
Glucose
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PhotorespirationPhotorespiration• Occurs on hot, dry, bright daysOccurs on hot, dry, bright days• Stomates closeStomates close• Fixation of OFixation of O22 instead of CO instead of CO22
• Produces Produces 2-C molecules 2-C molecules instead of 3-C sugar moleculesinstead of 3-C sugar molecules
• Produces Produces no sugarno sugar molecules molecules or or no ATPno ATP
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PhotorespirationPhotorespirationBecause of photorespiration, Because of photorespiration,
plants have special plants have special adaptations to limit the effect adaptations to limit the effect of photorespiration:of photorespiration:1.1. CC44 plants plants
2.2. CAM plantsCAM plants
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CC44 Plants Plants• Hot, moist Hot, moist
environmentsenvironments• 15% of plants 15% of plants
((grasses, corn, grasses, corn, sugarcane)sugarcane)
• Photosynthesis Photosynthesis occurs in 2 placesoccurs in 2 places
• Light reactionLight reaction - - mesophyll cellsmesophyll cells
• Calvin cycleCalvin cycle - - bundle sheath bundle sheath cellscells
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CC44 Plants Plants
Mesophyll CellMesophyll Cell
CO2
C-C-CPEP
C-C-C-CMalate-4C sugar
ATP
Bundle Sheath CellBundle Sheath Cell
C-C-CPyruvic Acid
C-C-C-CCO2
C3
Malate
Transported
glucoseVascular Tissue
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CAM PlantsCAM Plants• Hot, dry environmentsHot, dry environments• 5%5% of plants (cactus and ice of plants (cactus and ice
plants)plants)• Stomates closed during dayStomates closed during day• Stomates open during the nightStomates open during the night• Light reaction - occurs during Light reaction - occurs during
the daythe day• Calvin Cycle - occurs when COCalvin Cycle - occurs when CO22
is presentis present
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CAM PlantsCAM PlantsNight (Stomates Open) Day (Stomates Closed)
Vacuole
C-C-C-CMalate
C-C-C-CMalate Malate
C-C-C-CCO2
CO2C3
C-C-CPyruvic acid
ATPC-C-CPEP glucose
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Question:Question:
Why do CAM Why do CAM plants close plants close
their stomata their stomata during the day?during the day?
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Cam plants Cam plants close their close their
stomata in the stomata in the hottest part hottest part of the day to of the day to
conserve conserve waterwater