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Photosynthesis The Source of most Biological Energy Trapped in Photosynthesis Energy Converted to Chemical Bonds.

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Presentation on theme: "Photosynthesis The Source of most Biological Energy Trapped in Photosynthesis Energy Converted to Chemical Bonds."— Presentation transcript:

1 Photosynthesis The Source of most Biological Energy Trapped in Photosynthesis Energy Converted to Chemical Bonds

2 glycolysis cytosol Krebs cycle mitochondrion matrix ETS + Ox Phos mitochondrion cristae sugar pyruvate CO 2 NADH ATP O 2 H 2 O ATP sucrose synthesis cytosol Calvin cycle chloroplast stroma LR + P Phos chloroplast thylakoid sugar triose CO 2 NADPH ATP O 2 H 2 O Light Respiration:CH 2 O + O 2 CO 2 + H 2 O + ATP Photosynthesis:CH 2 O + O 2 CO 2 + H 2 O + light

3 Light: An Energy Waveform With Particle Properties Too wavelength (nm) 10 -9 meter 0.000000001 meter! 400 500 600 700 nm wavelength violetbluegreenyelloworangered

4 Light: An Energy Waveform With Particle Properties Too wavelength (nm) 10 -9 meter 0.000000001 meter! 400 500 600 700 nm wavelength visible spectrum

5 http://www.alanbauer.com/photogallery/Water/Rainbow%20over%20Case%20Inlet-Horz.jpg White light: all the colors humans can see at once

6 http://www.tvtome.com/images/shows/4/8/40-11946.jpg http://www.coreywolfe.com/NOV%202004/mlp.jpg http://www.astrostreasureches t.net/websmurfclub/images/pin smurfoncloudrainbow.jpg http://jojoretrotoybox.homestead.com/files/Rainbow_Brite_Logo_2.jpg http://www.chez.com/uvinnovatio n/site/images/introduction/apple_l ogo.gif Which side of our brains are we using?

7 White Light Leaf Pigments Absorb Most Colors Green is reflected!

8 Light: An Energy Waveform With Particle Properties Too amplitude brightness intensity Many metric units for different purposes We will use an easy-to-remember English unit: foot-candle 0 fc = darkness 100 fc = living room 1,000 fc = CT winter day 10,000 fc = June 21, noon, equator, 0 humidity

9 What wavelengths of light drive photosynthesis? wavelength (nm) 400 500 600 700 nm visible spectrum green light reflected Action Spectrum some still drives photosynthesis Photosynthetic Rate 0 100% Light beyond 700 nm has insufficient energy to drive photosynthesis

10 Antenna Pigment Complex Light energy transfer e-e- to: ETS Photosystem II chlorophyll b P450 lutein P470 zeaxanthin P480 ß-carotene P500 lycopene P510 chlorophyll b P650 chlorophyll a P680 e-e- from: H 2 O In each energy transfer some energy is lost as heat: 2 nd law of thermodynamics. But enough energy is passed to P680 to eject an electron to the electron transport system.

11 CH 2 CH 3 C2H5C2H5 HC H3CH3C H H H H3CH3C H N N N N H H Mg CH 3 O O=COCH 3 Chlorophyll a CH 2 CHO C2H5C2H5 HC H3CH3C H H H H3CH3C H N N N N H H Mg CH 3 O O=COCH 3 Chlorophyll b O CH CH 2 CH 3 H2CH2C C H2CH2C CH H2CH2C H2CH2C HC H2CH2C CH 2 O=C H3CH3C H3CH3C H3CH3C H3CH3C O CH CH 2 CH 3 H2CH2C C H2CH2C CH H2CH2C H2CH2C HC H2CH2C CH 2 O=C H3CH3C H3CH3C H3CH3C H3CH3C H3CH3C CH 3 CH CCH 3 HC CH 3 C HC CH HC H3CH3C CH HC CH C HC C H3CH3C H3CH3C H3CH3C CH 3 ß-CaroteneZeaxanthin H3CH3C CH 3 CH CCH 3 HC CH 3 C HC CH HC H3CH3C CH HC CH C HC C H3CH3C H3CH3C H3CH3C CH 3 HO OH Lutein Photosynthetic pigments are amphipathic

12 What intensities of light drive photosynthesis? Light Intensity (fc) 0 10 100 1,000 10,000 fc add to reserve grow reproduce Using reserves and may die Reaction Rate 0 100% Photosynthesis Respiration compensation point The example plant shown here breaks even at an intensity we have in our homes…a house plant!

13 What intensities of light drive photosynthesis? Light Intensity (fc) 0 10 100 1,000 10,000 fc Reaction Rate 0 100% Photosynthesis A Respiration compensation points The second example plant shown here cannot survive in our homes…it is a sun-loving crop plant! Photosynthesis B Shade tolerant plant dies in intense light!

14 reducing oxidizing -2.0 -1.5 -0.5 0 0.5 1.0 1.5 2.0 2 H 2 O O 2 + 4 H + 4 e - P680 P700 P680* P700* Pheo PQ cyt f PC cyt b FeS Fd FNR NADP + NADPH E m (volts) e - H+H+ PS II PS I The Z-scheme of the Light Reactions: An Energy Diagram ADP+P i ATP

15 The Calvin Cycle has Three Phases P-C-C-C-C-C-P ribulose-1,5- bisphosphate C-C-C-P glyceraldehyde- 3-phosphate C-C-C-P 3-phospho- glycerate CO 2 rubisco sucrose for transport starch for storage ADP ATP ADP + P i ATP NADPH NADP + regeneration carboxylation reduction

16 Lets Do Some Stoichiometry: P-C-C-C-C-C-P ribulose-1,5- bisphosphate C-C-C-P glyceraldehyde- 3-phosphate C-C-C-P 3-phospho- glycerate CO 2 rubisco sucrose for transport starch for storage ADP ATP ADP + P i ATP NADPH NADP + regeneration carboxylation reduction complex shuffling To take off 3 carbons: 3 3 6 6 6 6 6 6 6 1 5 3 3 5 x 3 = 15 C 3 x 5 = 15 C

17 More Stoichiometry: P-C-C-C-C-C-P ribulose-1,5- bisphosphate C-C-C-P glyceraldehyde- 3-phosphate C-C-C-P 3-phospho- glycerate CO 2 rubisco sucrose for transport starch for storage ADP ATP ADP + P i ATP NADPH NADP + regeneration carboxylation reduction complex shuffling To take off 3 carbons: 3 3 6 6 6 6 6 6 6 1 5 3 3 sucrose and starch are not 3-carbon compounds!

18 The Calvin Cycle and Light Reactions are interdependent The Calvin Cycle cannot operate in darkness! Dark Reactions? chlorophyll, etc. H 2 O O 2 ADP + P i ATPNADP + NADPH CO 2 (CH 2 O) 3 rubisco, etc. Light Reactions Calvin Cycle thylakoid stroma

19 Photosynthesis: Review and Expansion CO 2 + H 2 O O 2 + CH 2 O light chlorophyll We have been hiding considerable truth from you! Not 1 step… more like 50! Light Reactions: perhaps 25 steps H2OH2O light chlorophyll + ATPNADP +ADP + P ++ NADPH 2 O2O2 Calvin Cycle Reactions: perhaps 25 stepsAKA: Dark Reactions CO 2 CH 2 ONADPH 2 ++ NADPATP ++ ADP + P Interdependent! In sum:CO 2 + H 2 OO 2 + CH 2 O light chlorophyll The light and Calvin cycle reactions are interdependent… no dark reactions!

20 RuBisCO: an ancient enzyme with a modern problem RuBP + CO 2 RuBP + O 2 2 x P-C-C-C (a triose relative) P-C-C-C (a triose relative) + P-C-C 2 x CO 2 photorespiration O=O O=C=O 1% in air 20% in air RuBisCO Early in evolution of photosynthesis the atmosphere was anaerobic, so RuBisCo evolved without a problem. As photosynthesis was successful, competitive inhibition from oxygen was essentially a negative feedback. Evolution has not yet replaced RuBisCO. But several workarounds have evolved… RuBisCO often constitutes up to 40% of the protein in a plant…to ensure enough photosynthesis is achieved

21 C 4 Photosynthesis: The first fixation is a 4-carbon compound Mesophyll CellBundle Sheath Cell atm CO 2 HCO 3 - phosphoenol pyruvate C 4 acid C 3 acid C 4 acid C 3 acid Calvin cycle CO 2 pepc rubisco carboxylation decarboxylation plasmodesmata regeneration The C 4 and C 3 reactions are spatially separated

22 http://botit.botany.wisc.edu/images/130/Leaf/Zea_leaf_cross_section/ Major_vein_MC.jpg Zea mays C 4 Leaves http://www.uni-duesseldorf.de/home/Jahrbuch/2002/Grieshaber/Grafik/Grieshaber05.gif Flaveria bidentis http://www.conabio.gob.mx/malezasdemexico/a steraceae/flaveria-trinervia/imagenes/rama.jpg RubisCO expression in leaf cs PEPc expression in leaf cs http://wings.buffalo.edu/academic/department/fnsm/ bio-sci/facultyart.GIFS/Berryart.gif mesophyll bundle sheath

23 Zea mays leaf cross section showing classic Kranz anatomy

24 Zea mays leaf cross section These bulliform cells lose water and the leaf rolls…which way?

25 C 4 Photosynthesis: A cycle requiring ATP and NADPH Mesophyll CellBundle Sheath Cell atm CO 2 HCO 3 - CCCCOO- oxaloacetate Calvin cycle CO 2 pepc rubisco plasmodesmata The C 4 and C 3 reactions are spatially separated carbonic anhydrase -OOCCCCOO- malate PiPi malate dehydrogenase NADP + NADPH -OOCCCCOO- malate NADPH NADP+ CCCOO- pyruvate pyruvate- phopsphate dikinase ATP ADP CCCOO- phosphoenol pyruvate P malic enzyme NADP malic enzyme type

26 CAM Photosynthesis: Crassulacean Acid Metabolism At NightIn Daylight atm CO 2 HCO 3 - phosphoenol pyruvate pepc The C 4 and C 3 reactions are temporally separated starch triose phosphate oxaloacetate malate malic acid malic dehydrogenase NADH NAD + low pH starch malate malic acid malic enzyme pyruvate rubisco Calvin cycle CO 2 NADP+ NADPH higher pH stomata open!stomata closed!

27 Sedum leaf cross-section (a CAM plant) Note the lack of palisade/spongy differentiation

28 Sedum leaf cross-section (a CAM plant) Note the lack of Kranz anatomy


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