Unveiling Photosynthesis: The Light-Dependent Journey to Energy Conversion

2. Photosynthesis:LifefromLight andCO2

5. Energy needs of life • All life needs a constant input of energy • Heterotrophs (Animals) • Get energy…. • Convert energy…. • Autotrophs (Plants) • Ger energy… • convert energy… • build organic molecules (CHO) from CO2 consumers producers

6. glucose H2O CO2 N K P … What does it mean to be a plant • Need to… • collect light energy • transform it into chemical energy • store light energy • in a stable form to be moved around the plant or stored • need to get building block atomsfrom the environment • C,H,O,N,P,K,S,Mg • produce all organic moleculesneeded for growth • carbohydrates, proteins, lipids, nucleic acids ATP

7. Plant structure • What structures do the following? • Absorb sunlight • leaves = solar pigments • Obtain CO2 • stomates • H2O • uptake from roots • nutrients • N, P, K, S, Mg, Fe… • uptake from roots

8. stomate • transpiration • gas exchange

9. CO2 Chloroplasts absorbsunlight & CO2 cross sectionof leaf leaves chloroplastsin plant cell chloroplastscontainchlorophyll chloroplast makeenergy & sugar

10. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ outer membrane inner membrane stroma thylakoid granum chloroplast Plant structure ATP thylakoid • Chloroplasts • double membrane • stroma • fluid-filled interior • thylakoid sacs • grana stacks • Thylakoid membrane contains • chlorophyll molecules • electron transport chain • ATP synthase • H+ gradient built up within thylakoid sac

11. Photosynthesis • Light reactions • light-dependent reactions • energy conversion reactions • convert solar energy to chemical energy • ATP & NADPH • Calvin cycle • light-independent reactions • sugar building reactions • uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 It’s not theDark Reactions!

12. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ thylakoid chloroplast Light reactions ATP • Electron Transport Chain • like in cellular respiration • proteins in organelle membrane • electron carriers • NADPH • proton (H+) gradient across inner membrane • find the double membrane! • ATP synthase enzyme

13. Chemiosmosis of Respiration Mitochondria energy of mighty electrons is converted into chemical energy of ATP • use electron carrier NADH Consumes O2

14. Chemiosmosis of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP • use electron carrier NADPH Produces O2

15. H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ The ATP that “Jack” built photosynthesis respiration sunlight oxidation of C6H12O6 • moves the electrons • runs the pump • pumps the protons • builds the gradient • drives the flow of protons through ATP synthase • bonds Pi to ADP • generates the ATP … that evolution built ATP

16. Pigments of photosynthesis How does thismolecular structurefit its function?

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

18. Photosystems of photosynthesis • 2 photosystems in thylakoid membrane • Like solar grids that harvest light energy • Both have chl a in their reaction centers. reactioncenter What do the antenna pigments do? antennapigments

19. Light: absorption spectra Why areplants green?

20. Function of all pigments How can this be?

21. Photosystem II Photosystem I ETC of Photosynthesis chlorophyll a chlorophyll a

22. e e ETC of Photosynthesis sun 1 Photosystem IIP680chlorophyll a

23. 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

24. 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

25. 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

26. 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!

27. 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

28. 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 What conclusion is discerned from this data?

29. 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

30. 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

31. NADP Photophosphorylation cyclic photophosphorylation NONcyclic photophosphorylation ATP

32. 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

33. You can grow if you Ask Questions!

34. Ghosts of Lectures Past(storage)

35. Stomates