2Products of photosynthesis create ecosystems. Organic compounds produced by photosynthesisProvide the energy and building material for ecosystems.Energy for other organismsMake photoautotrophs the biological infrastructure of ecosystems.Ecosystems are defined by their PLANTS!
36 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O PhotosynthesisPhotosynthesis is summarized as6 CO H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O
4An overview of photosynthesis CO2LightLIGHT REACTIONSCALVINCYCLEChloroplast[CH2O](sugar)NADPHNADP ADP+ PO2Figure 10.5ATP
6QuizWhat is the summary equation for photosynthesis?Where does the light energy go?What role does Oxygen play in Cellular Respiration?
76 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O QuizWhat is the summary equation for photosynthesis? 3 pointsWhere does the light energy go? 3 PointsBonds in glucoseWhat role does Oxygen play in Cellular Respiration? (2 points) accepts H+ to form H2O6 CO H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O
810.2 Light reactionsThe light reactions convert solar energy to the chemical energy of ATP and NADPH.Harness energy in light
12Chlorophyll b, Carotenoids Chlorophyll aIs the main photosynthetic pigmentChlorophyll b, CarotenoidsAre accessory pigments
13Excitation of Chlorophyll by Light When a pigment absorbs lightIt goes from a ground state to an excited state, which is unstableExcitedstateEnergy of electionHeatPhoton(fluorescence)ChlorophyllmoleculeGrounde–Figure A
14(INTERIOR OF THYLAKOID) Primary electionacceptorPhotonThylakoidLight-harvestingcomplexesReactioncenterPhotosystemSTROMAThylakoid membraneTransferof energySpecialchlorophyll amoleculesPigmentTHYLAKOID SPACE(INTERIOR OF THYLAKOID)Figure 10.12e–A photosystemIs composed of a reaction center surrounded by a number of light-harvesting complexes
15The light-harvesting complexes Consist of pigment molecules bound to particular proteinsFunnel the energy of photons of light to the reaction center
16When a reaction-center chlorophyll molecule absorbs energy One of its electrons gets bumped up to a primary electron acceptorThe thylakoid membraneIs populated by two types of photosystems, I (P700) and II (P680)
17Noncyclic Electron Flow Is the primary pathway of energy transformation in the light reactions.Produces NADPH, ATP and O2.
18O2 e Energy of electrons Light P680 Photosystem II (PS II) H2O CO2 NADP+ADPCALVIN CYCLELIGHT REACTIONSATPNADPHO2[CH2O] (sugar)eEnergy of electronsLightP6801Photosystem II (PS II)
19O2 Primary acceptor e 2 H+ + 1⁄2 Energy of electrons P680 H2OCO2LightLIGHT REACTIONSCALVIN CYCLEO2NADP+NADPH[CH2O] (sugar)Photosystem II (PS II)ePrimary acceptorADPATP2 H++1⁄2132Energy of electronsP680
20Electron transport chain +H2OCO2LightLIGHT REACTIONSCALVIN CYCLENADP+NADPH[CH2O] (sugar)Photosystem II (PS II)ePrimary acceptorATP2 H+1⁄22Energy of electronsADPPqCytochromecomplexPcElectron transport chain43e5eP6801
21Electron transport chain H2OCO2LightLIGHT REACTIONSCALVIN CYCLENADPH[CH2O] (sugar)Photosystem II (PS II)ePrimary acceptor2 H+1⁄22Energy of electronsADPPqCytochromecomplexPcATPElectron transport chain5NADP+Photosystem I (PS I)6134+eeP700P680
22Electron transport chain +CO2Photosystem II (PS II)H2OLightLIGHT REACTIONSCALVIN CYCLEO2NADPH[CH2O] (sugar)ePrimary acceptor2 H+1⁄21Energy of electronsPqCytochromecomplexPcATPElectron transport chainNADP+Photosystem I (PS I)62ADP5FdElectronTransportchain7reductase+ 2 H+8+ H+34P680
23Under certain conditions Cyclic Electron FlowUnder certain conditionsPhotoexcited electrons take an alternative path.This involves only PSI and short circuits the system.But, does produce one ATP
24The light reactions and chemiosmosis: the organization of the thylakoid membrane REACTORNADP+ADPATPNADPHCALVINCYCLE[CH2O] (sugar)STROMA(Low H+ concentration)Photosystem IIH2OCO2CytochromecomplexO211⁄22Photosystem ILightTHYLAKOID SPACE(High H+ concentration)ThylakoidmembranesynthasePqPcFdreductase+ H+NADP+ + 2H+ToCalvincycleP3H+2 H++2 H+Figure 10.17
26An elegant experiment by Engelmann Illuminated a filament of green algae on a microscope slide using a prism to break up the light.Included an aerobic bacterium.Observed where the bacteria congregated.They need O2 and will move towards it.
27Englemann’s results. Where are the bacteria congregating? Why? What does that tell us.
29QuizWhat carbohydrate is produced directly from the Calvin Cycle?What are the three phases of the Calvin cycle?Where does O2 come from? What molecule?
30QuizWhat carbohydrate is produced directly from the Calvin Cycle? (2 Points) Glyceraldehyde 3-phosphate (or G3P)What are the three phases of the Calvin cycle? (3 points) Carbon Fixation, Reduction, Regeneration of RuBPWhat part of Photosynthsis generates O2 from? What molecule? (2 Points) Light Reactions, H2O
3110.3 The Calvin Cycle The Calvin cycle Is similar to the citric acid cycle (but in reverse)Occurs in the stromaUses the products from the light reactionsIs light independent.
32Calvin Cycle Three phases Carbon fixation Reduction Regeneration of the CO2 acceptor
346 simultaneous turns of the Calvin cycle Think of it this way…6 simultaneous turns of the Calvin cycle6 CO2‘s are fixed by 6 molecules of RuBP2 G3P’s pop out (2 x 3C’s = 6 C’s)1 molecule of Glucose (6C ÷ 6C = 1)10 G3P’s go to reform RuBP (10x3C’s = 30C’s)6 molecules (30C’s ÷ 5C’s = 6) of RuBP.
36Figure 10.18 The Calvin cycle (Entering oneat a time)CO23Phase 1: Carbon fixationRubiscoShort-lived intermediate3 PPRibulose bisphosphate (RuBP)3-Phosphoglycerate6 P1,3-Bisphosphoglycerate6 NADPH6 NADP+6 P i6Glyceraldehyde-3-phosphate(G3P)Phase 2: Reduction6 ATPCALVINCYCLE1G3P (a sugar) OutputGlucose andother organiccompounds6 ADPInputLightH2OLIGHT REACTIONSATPNADP+[CH2O] (sugar)CALVIN CYCLENADPHADPO26
37Figure 10.18 The Calvin cycle (Entering oneat a time)CO23Phase 1: Carbon fixationRubiscoShort-lived intermediate3 PPRibulose bisphosphate (RuBP)3-Phosphoglycerate6 P1,3-Bisphosphoglycerate6 NADPH6 NADP+6 P i6Glyceraldehyde-3-phosphate(G3P)Phase 2: Reduction6 ATP3 ATP3 ADPCALVINCYCLE5Phase 3: Regeneration of the CO2 acceptor (RuBP)1G3P (a sugar) OutputGlucose andother organiccompoundsG3P6 ADPLightH2OLIGHT REACTIONSNADPHNADP+[CH2O] (sugar)CALVIN CYCLEInputATPADPO26
38Alternative mechanisms of Carbon fixation On hot, dry days, plants close their stomataConserving waterLimits CO2Light reactions continueCausing oxygen to build upRubisco preferentially binds O2.Uses ATP w/out replacement.Decreases photosynthetic output.
39Leaf Anatomy (See p 725 for more details) Upper EpidermisCuticleMesophyllVeinStomateLower Epidermis
40C4 plants minimize the cost of photorespiration By incorporating CO2 into four carbon compounds in mesophyll cells.PEP Carboxylase to fix CO2.Forms OxaloacetateMoved to Bundle sheath cellsCalvin cycle occurs.Spatial separation of light and dark reactions.
41C4 leaf anatomy and the C4 pathway CO2Mesophyll cellBundle-sheathcellVein(vascular tissue)Photosyntheticcells of C4 plantleafStomaMesophyllC4 leaf anatomyPEP carboxylaseOxaloacetate (4 C)PEP (3 C)Malate (4 C)ADPATPSheathPyruate (3 C)CALVINCYCLESugarVasculartissueFigure 10.19
42During the day, the stomata close CAM PlantsCAM plantsOpen their stomata at night, incorporating CO2 into organic acids.During the day, the stomata closeAnd the CO2 is released from the organic acids for use in the Calvin cycle.Temporal separation of Light and Dark reactions.
44The Importance of Photosynthesis: A Review A review of photosynthesisLight reactions:• Are carried out by molecules in thethylakoid membranes• Convert light energy to the chemicalenergy of ATP and NADPH• Split H2O and release O2 to theatmosphereCalvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convertCO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactionsO2CO2H2OLightLight reactionCalvin cycleNADP+ADPATPNADPH+ P 1RuBP3-PhosphoglycerateAmino acidsFatty acidsStarch(storage)Sucrose (export)G3PPhotosystem IIElectron transport chainPhotosystem IChloroplastFigure 10.21
45Read Enzyme lab (#2) In your lab book. HomeworkRead Enzyme lab (#2) In your lab book.Pre-lab tomorrow.Exam on Monday C-7-10Finish review given out last week, do self quizzes and review quizzes on CD, think of potential essay questions!