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Pigments of photosynthesis

Pigments of photosynthesis. Chlorophylls & other pigments embedded in thylakoid membrane arranged in a “ photosystem ” collection of molecules structure-function relationship. How does this molecular structure fit its function?. A Look at Light. The spectrum of color. V. I. B. G. Y.

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Pigments of photosynthesis

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  1. Pigments of photosynthesis • Chlorophylls & other pigments • embedded in thylakoid membrane • arranged in a “photosystem” • collection of molecules • structure-function relationship How does thismolecular structurefit its function?

  2. A Look at Light • The spectrum of color V I B G Y O R

  3. Light: absorption spectra • Photosynthesis gets energy by absorbing wavelengths of light • chlorophyll a • absorbs best in red & blue wavelengths & least in green • accessory pigments with different structures absorb light of different wavelengths • chlorophyll b, carotenoids, xanthophylls Why areplants green?

  4. Photosystems of photosynthesis • 2 photosystems in thylakoid membrane • collections of chlorophyll molecules • act as light-gathering molecules • Photosystem II • chlorophyll a • P680 = absorbs 680nm wavelength red light • Photosystem I • chlorophyll b • P700 = absorbs 700nm wavelength red light reactioncenter antennapigments

  5. Photosystem II Photosystem I ETC of Photosynthesis chlorophyll a chlorophyll b

  6. e e ETC of Photosynthesis “Bouncing Ball” example sun 1 Photosystem IIP680chlorophyll a

  7. H H O e e H+ H H +H e- e- H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ETC of Photosynthesis Inhale, baby! thylakoid chloroplast ATP Plants SPLIT water! 1 2 O O e e fill the e– vacancy Photosystem IIP680 chlorophyll a

  8. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ e e e e to Calvin Cycle ADP + Pi H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ETC of Photosynthesis thylakoid chloroplast ATP 3 1 2 ATP 4 energy to buildcarbohydrates Photosystem IIP680 chlorophyll a ATP Photophosphorylation

  9. e e e e e e ETC of Photosynthesis sun fill the e– vacancy 5 e e Photosystem IP700 chlorophyll b Photosystem IIP680 chlorophyll a

  10. e e e e NADPH toCalvin Cycle ETC of Photosynthesis electron carrier 6 5 sun Photosystem IP700 chlorophyll b Photosystem IIP680 chlorophyll a $$ in the bank…reducing power!

  11. e e e e H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ETC of Photosynthesis sun sun O to Calvin Cycle split H2O ATP

  12. ETC of Photosynthesis • ETC uses light energy to produce • ATP & NADPH • go to Calvin cycle • PS II absorbs light • excited electron passes from chlorophyll to “primary electron acceptor” • need to replace electron in chlorophyll • enzyme extracts electrons from H2O & supplies them to chlorophyll • splits H2O • O combines with another O to form O2 • O2 released to atmosphere • and we breathe easier!

  13. Learning Check • Compare/ Contrast the Electron transport Chains of Photosynthesis and Respiration

  14. Experiment 1 Experiment 2 light energy light energy light energy    6CO2 6CO2 6CO2 + + + 6H2O 6H2O 6H2O + + + + + + 6O2 6O2 6O2 C6H12O6 C6H12O6 C6H12O6 Experimental evidence • Where did the O2 come from? • radioactive tracer = O18 Proved O2 came from H2O not CO2 = plants split H2O!

  15. Noncyclic Photophosphorylation • Light reactions elevate electrons in 2 steps (PS II & PS I) • PS II generates energy as ATP • PS I generates reducing power as NADPH ATP

  16. Noncyclic Simulation • 6 Volunteers • Sun • PSII • ADP/ATP • PSI • NADP+/NADPH • Calvin Cycle • Materials: • White H atoms (energy packets) • Glass of water • 2 test tube racks • Candy

  17. NoncyclicPhotophosphorylation • What is limiting the Calvin Cycle? • What is produced in excess? • How can the stroma accumulate more ATP?

  18. Cyclic photophosphorylation • If PS I can’t pass electron to NADP…it cycles back to PS II & makes more ATP, but no NADPH • coordinates light reactions to Calvin cycle • Calvin cycle uses more ATP than NADPH  ATP 18 ATP +12 NADPH  1 C6H12O6

  19. NADP Photophosphorylation cyclic photophosphorylation NONcyclic photophosphorylation ATP

  20. Photosynthesis summary Where did the energy come from? Where did the electrons come from? Where did the H2O come from? Where did the O2 come from? Where did the O2 go? Where did the H+ come from? Where did the ATP come from? What will the ATP be used for? Where did the NADPH come from? What will the NADPH be used for? …stay tuned for the Calvin cycle

  21. You can grow if you Ask Questions!

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