1. Slide 1 Chapter 11: Phototrophic Energy Metabolism: Photosynthesis

2. Slide 2 Photoheterotrophs vs. Photoautotrophs

3. Slide 3 Photosynthesis Overview Energy Transduction Reactions (aka the “light reactions”)Energy Transduction Reactions (aka the “light reactions”) Light energy is captured by chlorophyllLight energy is captured by chlorophyll Reducing power is generated in the form of NADPHReducing power is generated in the form of NADPH Carbon Assimilation Reactions (aka the “dark reactions”, the Calvin cycle)Carbon Assimilation Reactions (aka the “dark reactions”, the Calvin cycle) Carbon dioxide is fixed and reducedCarbon dioxide is fixed and reduced

4. Slide 4 The Chloroplast

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6. Slide 6 Cyanobacterium

7. Slide 7 Light Electromagnetic radiation with both wave and particle propertiesElectromagnetic radiation with both wave and particle properties Photon – discreet particle of lightPhoton – discreet particle of light Quantum – packet of energy carried by the photonQuantum – packet of energy carried by the photon Energy carried by photon is inversely proportional to the wavelengthEnergy carried by photon is inversely proportional to the wavelength Pigment – light absorbing moleculePigment – light absorbing molecule Photoexcitation – photon energy is used to excite an electronPhotoexcitation – photon energy is used to excite an electron

8. Slide 8 Chlorophyll

9. Slide 9 Photosystems Combination of chlorophyll molecules, accessory pigments, and associated proteins (all arranged into a functional unit)Combination of chlorophyll molecules, accessory pigments, and associated proteins (all arranged into a functional unit) Localized to thylakoid or bacterial membranesLocalized to thylakoid or bacterial membranes

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13. Slide 13 Summary of Photosystems Electrons move from water to NADPHElectrons move from water to NADPH Called non-cyclic electron flowCalled non-cyclic electron flow 4 photons absorbed in PSII, 4 in PSI, 8 total4 photons absorbed in PSII, 4 in PSI, 8 total 2 NADPH molecules generated2 NADPH molecules generated 12 protons pumped12 protons pumped

14. Slide 14 ATP Synthesis PhotophosphorylationPhotophosphorylation Very similar to ATP synthesis in cellular respirationVery similar to ATP synthesis in cellular respiration Approximately 1 ATP for every four protonsApproximately 1 ATP for every four protons

15. Slide 15 Cyclic Electron Flow

16. Slide 16 The Calvin Cycle Named after Melvin CalvinNamed after Melvin Calvin Won a Nobel prize in 1961Won a Nobel prize in 1961 Elucidated through the use of radiolabeled isotopesElucidated through the use of radiolabeled isotopes Occurs in the stroma of chloroplastsOccurs in the stroma of chloroplasts Split into 3 stages:Split into 3 stages: Carboxylation of Ribulose-1,5-BisphosphateCarboxylation of Ribulose-1,5-Bisphosphate Reduction of 3-phosphoglycerateReduction of 3-phosphoglycerate Regeneration of acceptor moleculeRegeneration of acceptor molecule

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19. Slide 19 Carbohydrate Synthesis

20. Slide 20 The Glycolate Pathway Remember: Rubisco normally has carboxylase activityRemember: Rubisco normally has carboxylase activity It also has oxygenase activityIt also has oxygenase activity Produces 2 carbon molecule: phosphoglycolateProduces 2 carbon molecule: phosphoglycolate Phosphoglycolate cannot be used in Calvin CyclePhosphoglycolate cannot be used in Calvin Cycle Why would evolution favor this?Why would evolution favor this? How do plants deal with it?How do plants deal with it?

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22. Slide 22 C4 Plants Carbon is fixed into 4 carbon molecule instead of 3Carbon is fixed into 4 carbon molecule instead of 3 Plants adapted to hot, arid environments with lots of sunshine (tropical grasses, maize, sugarcane, etc)Plants adapted to hot, arid environments with lots of sunshine (tropical grasses, maize, sugarcane, etc) Strategy: Isolate rubisco in cells that have high CO 2 levelsStrategy: Isolate rubisco in cells that have high CO 2 levels

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24. Slide 24 The Hatch- Slack Cycle

25. Slide 25 CAM plants Crassulacean Acid MetabolismCrassulacean Acid Metabolism Cacti, succulents, orchids, etc. (where water is limited)Cacti, succulents, orchids, etc. (where water is limited) Strategy: Segregate reactions by time (rather than space as in C4 plants)Strategy: Segregate reactions by time (rather than space as in C4 plants) Only open stomata at nightOnly open stomata at night