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Photosynthesis and some generally interesting facts about plants and whatnot

Biophysical Seminar 2011. December 2. Photosynthesis and some generally interesting facts about plants and whatnot. Bence Ferdinandy Physics MSc II. Introduction. Bence Ferdinandy – Biophysics Seminar 2011 . december 2. Introduction. Dark phase binding of CO 2 sugar synthesis.

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Photosynthesis and some generally interesting facts about plants and whatnot

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  1. Biophysical Seminar 2011. December 2. Photosynthesis and some generally interesting facts about plants and whatnot BenceFerdinandy Physics MSc II.

  2. Introduction BenceFerdinandy– Biophysics Seminar 2011.december 2.

  3. Introduction • Dark phase • binding of CO2 • sugarsynthesis • Light phase • binding of energy • emission of oxigen BenceFerdinandy– Biophysics Seminar 2011.december 2.

  4. Outline of thetalk • The anatomy of Photosynthesis • The Lightphase • The Darkphase • Problems: photorespiration • The efficiency of photosynthesis BenceFerdinandy– Biophysics Seminar 2011.december 2.

  5. The plantcell (EM pic) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  6. The plantcell (cartoon) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  7. Endosymbiothictheory • Ourancestorprotistaatebacterialikethings: • mithochondria and chloroplast • Evidence: • doublemembrane • own DNA • lot of thingssimilartobacteria • they replicate separately (wegetourmother’s) Wearenotaloneinourowncells! Shockingpiece of information BenceFerdinandy– Biophysics Seminar 2011.december 2.

  8. Chloroplast (EM pic) P M Grana (thylakoidmembrane) Lamella (thylakoidmembrane) BenceFerdinandy– Biophysics Seminar 2011.december 2. .

  9. Chloroplast (cartoon) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  10. Purpose of thelightphase:highenergymolecules ATP: Adenosinetriphosphate Veryimportant, (almost) everythingworkswithit. Made inmitchondriaalso. NADPH: Nicotinamideadeninedinucleotidephosphate BenceFerdinandy– Biophysics Seminar 2011.december 2.

  11. Lightphase I. (theelectrontransportchain) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  12. Lightphase I. (theelectrontransportchain) „OUTSIDE” „INSIDE” BenceFerdinandy– Biophysics Seminar 2011.december 2.

  13. Lightphase I. (theelectrontransportchain) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  14. The heart of itall: thePhotosystem Whathappens here? BenceFerdinandy– Biophysics Seminar 2011.december 2.

  15. Photosystem II Quite a beautyifyaaskme. BenceFerdinandy– Biophysics Seminar 2011.december 2.

  16. The lightharvestingcomplex of thePhotosystems The harvestingcomplex: Energytransferwith FRET Specialpair Chlorophyll-Amolecule BenceFerdinandy– Biophysics Seminar 2011.december 2.

  17. Onephotonexcitesoneelectron BenceFerdinandy– Biophysics Seminar 2011.december 2.

  18. The electron is passedto a plastoquinone One PQ cantaketwoelectrons BenceFerdinandy– Biophysics Seminar 2011.december 2.

  19. Plastoquinonetakesuptwoprotonsfromthestroma („outside”) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  20. Plastoquinonegivesthetwoelectronstocytochrome And thetwoprotonstothe lumen („inside”) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  21. PSII losttwoelectrons: itsplitswatertogetelectrons, one H2O = e- Risky! 2 H2O = O2 + 2 p+ -> more protons „inside” BenceFerdinandy– Biophysics Seminar 2011.december 2.

  22. Cytochrometransfersthetwoelectronstoplastocyanin Two more protonsarepumpedtothe lumen („inside”) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  23. Plastocyanintakesthetwoelectronsto PSI The electronsarenowgroundstate: theirenergylostinthetransfer and proton pumping BenceFerdinandy– Biophysics Seminar 2011.december 2.

  24. Electronsareexcited again and transferedtothetheFerredoxin NADP Reductasebyferredoxin BenceFerdinandy– Biophysics Seminar 2011.december 2.

  25. The FNR putstheenergy of theelectronsinto NADPH BenceFerdinandy– Biophysics Seminar 2011.december 2.

  26. Nowthere’s a concentrationgradient of protons, sotheprotons go back „outside” throughthe ATP synthase. BenceFerdinandy– Biophysics Seminar 2011.december 2.

  27. The energy of thegradient is storedin ATP. ATP synthase is like a turbine and is rotatedbythe proton flow. BenceFerdinandy– Biophysics Seminar 2011.december 2.

  28. Lightphase II. BenceFerdinandy– Biophysics Seminar 2011.december 2.

  29. Lightphase III. 2 H2O , 4 photons 2 NADPH , 3 ATP ,1 O2 12 protonspumped BenceFerdinandy– Biophysics Seminar 2011.december 2. .

  30. Absortionspectrum of chlorophyll BenceFerdinandy– Biophysics Seminar 2011.december 2.

  31. Excitationlevels of chlorophyll S3 S2 S1 T1 S0 light BenceFerdinandy– Biophysics Seminar 2011.december 2.

  32. Excitationlevels of chlorophyll S3 Fastenergyloss S2 photosynthesis S1 T1 S0 light BenceFerdinandy– Biophysics Seminar 2011.december 2.

  33. Excitationlevels of chlorophyll Fluorescence S3 Fastenergyloss Phosphorescence S2 photosynthesis S1 T1 S0 light BenceFerdinandy– Biophysics Seminar 2011.december 2.

  34. Darkphase I: RuBisCO Ribulose-1,5-bisphosphate carboxylaseoxygenase: The most abundant protein onEarth. BenceFerdinandy– Biophysics Seminar 2011.december 2.

  35. Darkphase II: Calvin-cycle • RuBisCO + 3 RuBP (5C) + 3 CO2 3 pc. 6C 6 pc. 3PGA (3C) • 13 steps, energyconsumingprocess (Calvin cycle) • 1 G3P (3C) • 3 RuBp • 2 G3P 1 glucose(6C) • theenergyusedduringthis: • 12 NADPH • 18 ATP 24 photons BenceFerdinandy– Biophysics Seminar 2011.december 2.

  36. Calvin cycle BenceFerdinandy– Biophysics Seminar 2011.december 2.

  37. Photorespiration • RuBisCOcan take O2 as substrate, createsuselessproduct • (concentrationdependent) • reversingtheproductneedsenergy, processloses C • it is donebythephotorespirationcomplex • (chloroplast + mitochondrion + peroxisome) • types of photosynthesis: C3, C4, CAM BenceFerdinandy– Biophysics Seminar 2011.december 2.

  38. C3 Photosynthesis • Typical (85%) • Justexplainedhowitworks • Fixes CO2into C3 product • Inefficientin hot and drycircumstances, becauseleaves „close” (don’tlosewater, can’ttakeup CO2 BenceFerdinandy– Biophysics Seminar 2011.december 2.

  39. C4 Photosynthesis • Spatialseparation • Fixes CO2inoutercellwith PEP (anotherensym) to C4 product • C4 into CO2ininnercell • Calvin cycleininnercell • RuBisCodoesn’tmeethighconcentration of oxygen • Example: sugarcane, corn BenceFerdinandy– Biophysics Seminar 2011.december 2.

  40. CAM Photosynthesis • Temporalseparation, 1 cell • Fixes CO2with PEP duringnightwhile Calvin cycle is notgoing • Closescellduringday and doesCalvin cycle Example: Cactus, pineapple BenceFerdinandy– Biophysics Seminar 2011.december 2.

  41. Efficiency I. • Loses of energyduringthewholeprocess: • ~30% - crosssection • ~47% - limited absorbtionrange • ~24% - usesenergy of redquantaonly • ~68% - duringtheglucoseproduction • ~35-45% - photorespiration and such • thisestimategives 5-6% efficiency BenceFerdinandy– Biophysics Seminar 2011.december 2.

  42. Efficiency II. • Theoretical: 30% (includingtheenergyloss of chemicalreactions • Laboratoryconditions: 25% • Naturalconditions: • inDeath Valley (wintereveningprimrose): 8% • sugarcane: 7% (remember, it’s C4) • most crops: 1-4 % • This 1-7% is alsousedtoupkeeping, growing, reproduction BenceFerdinandy– Biophysics Seminar 2011.december 2.

  43. Efficiency III. • Comparisonwithsolarpanels: • theoretical: 86% • laboratory: > 40 % • commercial (cheap/notsocheap): ~6% / 15-20% • BUT: theplant is a self-replicating, self-maintainingsolarcell, and enviromentfriendly(no rareelementsneeded) BenceFerdinandy– Biophysics Seminar 2011.december 2.

  44. Whatwehavelearned • the anatomy of thephotosynthetic apparatus: chloroplast • lightphase: electrontransportchain, watersplitting, O2 making • generateshighenergymolecules, uses proton gradient • darkphase: CO2fixationwithRuBisCO + energy=glucose • photorespiration: RuBisCOcan fix O2aswell -> C3, C4, CAM paths • efficiency: below 10% BenceFerdinandy– Biophysics Seminar 2011.december 2.

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