10. Photosynthesis: pgs 172-187 Key ConceptsSlide 2An Overview of PhotosynthesisSlide 4Slide 5Slide 6How Did Eukaryotic Cells Originate?The Structure of the ChloroplastSlide 9Photosynthesis: Two Linked Sets of ReactionsSlide 11The Electromagnetic SpectrumPhotosynthetic Pigments Absorb LightEach Pigment Has a Specific Absorption SpectrumSlide 15The Role of Carotenoids and Other Accessory PigmentsThe Structure of ChlorophyllElectrons Become Excited When Light Is AbsorbedFluorescencePhotosystemsThe Antenna ComplexThe Reaction CenterThe Discovery of Photosystems I and IISlide 24How Does Photosystem II Work?Electrons from Pheophytin Enter an ETCElectrons Participate in Redox ReactionsSlide 28Slide 29Chemiosmosis and PhotophosphorylationHow Does Photosystem II Obtain Electrons?Oxygenic and Anoxygenic PhotosynthesisThe Importance of Oxygenic PhotosynthesisHow Does Photosystem I Work?NADPH Is an Electron CarrierSummary of Photosystems I and IIHow Does Photosynthesis Convert Light Energy into Chemical Energy?The Z Scheme: PS I and II can work togetherSlide 39The Z SchemeThe Enhancement EffectSlide 42Slide 43The Location of Photosystem I and Photosystem IISlide 45The Calvin Cycle and Carbon FixationSlide 47Slide 48The Importance of RubiscoSlide 50© 2011 Pearson Education, Inc.10. Photosynthesis: pgs 172-187 Key ConceptsPhotosynthesis is the conversion of light energy to chemical energy stored in the bonds of carbohydrates. It consists of two linked sets of reactions. In the light-capturing reactions, excited electrons are used to produce the electron carrier NADPH or are donated to an electron transport chain, which results in the production of ATP via chemiosmosis. In the Calvin cycle, the enzyme rubisco catalyzes the addition of CO2 to a five-carbon compound. Subsequent reactions use the ATP and NADPH synthesized in the light reactions, yielding a molecule required for carbohydrate production.© 2011 Pearson Education, Inc.Autotrophs vs Heterotrophs?© 2011 Pearson Education, Inc.An Overview of Photosynthesis•Photosynthesis is the process of using sunlight to produce carbohydrate. This process requires sunlight, carbon dioxide, and water, and produces oxygen as a by-product. The overall reaction when glucose is the carbohydrate can be written as:6 CO2 + 12 H2O + light energy  C6H12O6 + 6 O2 + 6 H2O•Photosynthesis contrasts with cellular respiration.–Photosynthesis is endergonic.–Reduces CO2 to sugar–Cellular respiration is exergonic.–Oxidizes sugar to CO2Text section whereyou can find moreinformationENERGY FOR LIFEbegins asElectromagnetic energy inSUNLIGHT10.2drivesbegins with10.110.2PHOTOSYNTHESIS(in chloroplasts)• Light excites electrons in pigment moleculesAntenna complexentersH2O• “Splits” water to yield electrons• Electron transport chain pumps H+Photosystem II10.310.3• Electron transport chain ends with ferrodoxinPhotosystem Idonatesenergyfrom excitedelectrons todonatesenergyfrom excitedelectrons todonateshigh-energyelectrons to• H+ gradient drives ATP synthaseChemiosmosisreleases yieldsO2ATP9.1NADPHused inCO2• Series of enzyme-catalyzed reactionsCalvin cycle10.4fixed byrubiscoto startyields substratefor synthesis ofstored asbroken downto yieldGlycogen, starch5.2 5.1GLUCOSEBig Picture:Text section whereyou can find moreinformationENERGY FOR LIFEbegins asElectromagnetic energy inSUNLIGHT10.2drivesbegins with10.110.2PHOTOSYNTHESIS(in chloroplasts)• Light excites electrons in pigment moleculesAntenna complexentersH2O• “Splits” water to yield electrons• Electron transport chain pumps H+Photosystem II10.310.3• Electron transport chain ends with ferrodoxinPhotosystem Idonatesenergyfrom excitedelectrons todonatesenergyfrom excitedelectrons todonateshigh-energyelectrons to• H+ gradient drives ATP synthaseChemiosmosisreleases yieldsO2ATP9.1NADPHused inCO2• Series of enzyme-catalyzed reactionsCalvin cycle10.4fixed byrubiscoto startyields substratefor synthesis ofstored asbroken downto yieldGlycogen, starch5.25.1GLUCOSEprocessed by9.3• 10 enzyme-catalyzed reactionsGlycolysis (in cytosol)CELLULAR RESPIRATION(in mitochondria)allows continuedwhen electron acceptoravailable, yields pyruvate for9.2• Regenerates NAD+• Substrates and waste products vary among speciesFermentation9.7when no electronacceptor available, donates electrons tobegins withCO2H2OO2NADHATP• Catalyzed by pyruvate dehydrogenasePyruvate processing9.4yields acetyl CoA for9.5• 8 enzyme-catalyzed reactions• Completes oxidation of glucoseCitric acid cycleyields yieldsCO2FADH2donateshigh energyelectrons toused in• Raises potential energyPhosphorylation of enzymesand substrates9.1drives• Uses energy released during redox reactions to transport H+• Ends with final electron acceptor (usually O2)Electron transport chain9.6• H+ gradient drives ATP synthaseChemiosmosisyields someyields lots of9.1• Reactions that were endergonic with unphosphorylated enzymes/substrates become exergonic with phosphorylated enzymes/subtratesEnergetic couplingenablesCells use energy to do work• pump ions• synthesize molecules• move cargo• send and receive signalsBig Picture:© 2011 Pearson Education, Inc.All organisms perform Respiration/ FermentationOnly a select group also capable of Photosynthesis© 2011 Pearson Education, Inc.How Did Eukaryotic Cells Originate?Eukaryotic cells appeared about 1.5 billion years ago.Endosymbiosis theory  Cells engulfed other cells that became mitochondria and chloroplasts.Chloroplast of algae and plants evolved from endosymbiotic CyanobacteriaDouble membrane?© 2011 Pearson Education, Inc.The Structure of the Chloroplast •Photosynthesis occurs in the chloroplasts of green plants, algae, and other photosynthetic organisms.•Chloroplasts are surrounded by two membranes.•The internal membranes of chloroplasts form flattened, vesicle-like structures called thylakoids, some of which form stacks called grana. –Thylakoid membranes contain large quantities of pigments.–The most common pigment is chlorophyll.•The fluid-filled space between the thylakoids and the inner membrane is the stroma.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Photosynthesis: Two Linked Sets of ReactionsPhotosynthesis consists of two linked sets of reactions: light-dependent reactions produce O2 from H2O, and Calvin cycle reactions produce sugar from CO2.•The reactions are linked by electrons, which are