Photosynthesis Part 1Chapter 10 Pages 185-199Absorbing lightLight Reactions Energy Harvested Preview / ReviewEnergy   MatterRedox RXNSLaws of ThermodynamicsKinetic VS Potential EnergyFollow CarbonsFollow ElectronsCarbon CycleElectron transport chain & chemiosmosisATP synthase Exergonic – release of energyEnderogonic- taking in of energy Photosynthesis is Endergonic Thylakoid – disk structure arranged in a stackThey have a membrane, which causes two compartmentsStroma – outside the Thylakoid spaceThylakoid Space is inside the thylakoid Nature of light - Form of energy on electromagnetic spectrum from 380-750 nm- Both particle and wave properties - Wavelength = distance between crests - Inverse relationship with inverse to wavelengtho Shorter wave = more energy - Chlorophyl is just one of many pigments that organisms have Pigments- substances that selectively absorb visible light- Chlorophyl Ao- Chlorophyl Bo- CarotenoidsThe rate of photosynthesis DOES change over different wavelengths.What happens to absorbed light?- Photon hits pigment, e- excited, then falls- Dissipation (fig 10.11) *********o Emit Photon of light: Fluorescenceo Emit heato Transfer e- to other pigment: Resonance transfer Electron Transport chains are series of Redox Reactions Light Reactions:Converting solar energy to chemical energy1) Light harvesting complexes (PSII and PSI)a. Within thylakoid membraneb. Contain proteins and few 100 pigmentsc. Outer pigments absorb purple wavelengths, inner absorb redd. Excited e- energy transferred via resonance transfer from high E  low E2) LINEAR ELECTRON FLOW—PRODUCES ATP AND NADPHa. Photons excite e- in pigments and energy transferred to pair of chlorophyll a= P680, donates e- to a primary acceptor in the reaction complexb. P680 “strongest oxidizing agent in the world” c. Rips 2 e- from WATER (not light!)d. Water donates 2 e- to excited P680+, one by one e. E= “fall down” e- transport chain via redox rxns to PSI e- acceptor P700f. Additional photons excite these e- g. Cytochrome complex in 1st e- chain pumps H+ into thylakoid space—WHAT WILL THIS DO?i. Supplies the gradient to fuel the ATP Synthase and create ATPh. Excited e-form P700 “fall down” 2nd e-transport chain via Ferredoxin (fd) to electron shuttle = NADPH 3) Cyclin electron flow—Produces ONLY ATP (Damage control mechanism)a. Uses PSIFd (Ferradoxin) cytochrome complexb. Creates proton gradient ATP synthasesChapter 10 Pages 198-203Calvin CyclePhotorespiration Overview of Calvin Cycle- What does cycle mean?o Something needs to be regenerated- What is C input? C output?- What types of energy are used- Is it catabolic or anabolic? (anabolic process)- Following NET synthesis of ONE G3P- Need 3 turns of the cycle for one G3PMelvin CALVIN CycleImportant because the sugars are made in this cycle1) PHASE 1: CARBON FIXATIONa. (3X) CO2 + 5-C RuBP 6-C  2 3-Cb. Rubisco—most abundant enzyme on earth 2) PHASE 2: REDUCTIONa. Input ATP (6ATP/3 cycles)b. Input 2e- (6NADPHNADP+/3 cycles)c. Output 1 3-C G3P3) PHASE 3: REGENERATION of RuBP (CO2 acceptor)a. 5 3-c rearranged to 3 5-C RuBPb. Input 3 ATP / 3 CyclesHow many ATP & NADPH required to make 1 glucose? 18 ATP and 12 NADPH Two cycles because glucose has 6 carbons. Photorespiration:An evolutionary relic that causes problems- Ancient Atmosphereo Before photosynthesis: A lot more CO2 a lot less O2o Cyanobacteria 1st to photosynthesize 2.7 billion years ago- Ancient Atmosphere- Rubisco can bind CO2 OR O2 –When?- Rubisco- Ribulose bisphosphate carboxylase oxygenaseo Rubisco  W/ CO2 = 2(3 carbon phosphoglycerate)o Rubisco O2 1 (3-phosphoglycerate) and 1 (2-carbon compound)- Why is this a problem?o Releases CO2o Uses ATP in the Processo Decreases photosynthesis output by 25-50%C4 plants –Change in placeIncludes many grassesAnatomical adaptations:- Mesophyll cells—fix carbon to 4-C compound- Bundle sheath cells—release CO2 and proceed w/ Calvin Cycle- Need to invest energy to make system work- Bundle-sheath only have PSI, so only carry out cyclic e- flowCAM PLANTS –Change in time- includes succulents-cacti, pineapple, etc- Timing adaptations:o Stomata open @ night ONLYo Fix CO2 into organic acids- During day CO2 release and