1. Photosynthesis “Life is Bottled Sunshine” Wynwood Reade, Martyrdom of Man, 1872 Eva Farre, s150

2. Topics 1.Overview of photosynthesis 2.Key early photosynthesis experiments 3. Photosynthesis: light reactions

3. Where does the oxygen in the atmosphere come from? Was the oxygen concentration constant? What are the necessary components of photosynthesis? What is the overall reaction of photosynthesis? Which is the order of events?

4. CONSTITUENT CHEMICAL SYMBOL MOLE PERCENT Nitrogen N2 78.084 Oxygen O2 20.947 Argon Ar 0.934 Carbon Dioxide CO2 0.035 Others ATMOSPHERE COMPOSITION http://www.globalchange.umich.edu/

5. H20 + CO2 CH20 + O2

6. History: From air to starch Stephen Hales (1677-1761): Plants assimilated “air” Joseph Priestley (1733–1804) : plants can “purify” air Jan Ingen-Housz (1730-1799): this was dependent on light Jean Senebier (1742–1809) :”fixed air” (CO2) is essential for photosynthesis Pierre Joseph Pelletier (1788– 1842) and Joseph Bienaimé Caventou (1795–1877): chlorophyll Hugo von Mohl (1805–1872) discovered chloroplasts in plant cells Julius Robert Mayer (1814–1878): plants convert light energy into chemical energy Julius von Sachs (1832–1897 ): starch granules are product of photosynthesis

7. Where does the oxygen come from ? Photosynthesis is a redox reaction H20 + CO2 CH20 + O2 Van Niel (1920s) analyzed the photosynthesis of purple bacteria: nCO2 + 2 nH2O + light  (CH2O)n + nO2 + nH2O nCO2 + 2nH2S + light  (CH2O)n + 2nS + nH2O (Ziong et al., 2000, Science) “Purple bacteria are the earliest emerging photosynthetic lineage” OXYGENIC / ANOXYGENIC photosynthesisLIGHT/ DARK or CARBON-LINKED reactions Hill equation (1937):H20 + A + light  ½ O2 + H2A

8. (Des Marais, 2000. Science)

9. Topics 1.Overview of photosynthesis 2.Key early photosynthesis experiments 3. Photosynthesis: light reactions

10. Oxygenic Photosynthesis Light Reactions ATP NADPH Carbon Reactions H 2 0 O 2 CO 2 CH 2 0

11. Chloroplast structure

12. Photosynthesis Light Reactions (Simplified) e- e-Donor (H 2 0) Oxidized-e-Donor (O 2 ) e-acceptor (NADP) Reduced e-acceptor (NADPH) H+H+ H+H+ ADP + Pi ATP Thylakoid Lumen Stroma

13. Absorbance of light: Photochemistry

14. E = h (c/λ) Light absorption and emission of chlorophyll

16. Engelmann Experiments (1843 – 1909) Spyrogyra up to ~200 um long

17. Photosynthetic Pigments Absorption Spectra

18. Photosynthetic Pigments : Structure

19. Chlorophyll Organism a b c d Carotinoids Phycobilins Plants + + - - + - Green algae + + - - + - Diatoms + - + - + - Dinoflagelates + - + - + - Brown and yellow algae + - + - + - Red algae + - - + + - Cyanobacteria + - - - + +

20. Photochemical quantum yield/ efficiency: Φ = Number of photochemical products Total number of quanta absorbed (energy of a photon) Energy efficiency: = Notal number of quanta absorbed Photosynthesis products (ATP/NADPH) Important photosynthesis concepts

21. Red light enhancement effect (~1950s) : 2 photochemical complexes (~1960)

22. Z- Scheme of photosynthesis

24. Topics 1.Overview of photosynthesis 2.Key early photosynthesis experiments 3. Photosynthesis: light reactions

25. Next lecture: -Electron Transport Details (check respiration) -Regulation of the Photosynthetic Machinery -Genetics and Evolution of Photosynthetic Systems