Photosynthesis

• 1. Why are plants so important? Why are plants green? Which are the main pigments in a plant? What plants produce? Which materials are used to poduce organic materials? What do they release during this process? What is the name of this process?

2. Aim: to introduce the students to the processof photosynthesisObjectives: Recognize the importance of photosynthesis for oursurvival; Identify the reactants and products of photosynthesis;To draw the absorption and action spectrum ofphotosynthesisExplain and illustrate the two phases of photosynthesis. 3. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 4. What is photosynthesis? Photosynthesis is the process by which autotrophicorganisms use light energy to make sugar and oxygen gasfrom carbon dioxide and water 5. Photosynthesis in Overview In this process plants and other autotrophs store the energy of sunlight into sugars. Requires sunlight, water, and carbon dioxide. Overall equation:6 CO2 + 6 H20 C6H12O6 + 6 O2 6. Where does photosynthesis take place? Occurs in theleaves of plantsin organellescalled chloroplasts. 7. Leaf 8. The location and structure of chloroplasts ChloroplastLEAF CROSS SECTION MESOPHYLL CELLLEAF Mesophyll CHLOROPLAST Intermembrane spaceOutermembrane Granum InnermembraneGranaStroma ThylakoidStromaThylakoid compartment 9. Chloroplast Structure Have 2 membranes A bi-bilayer! The inner membrane iscalled the thylakoid. The thylakoid is foldedand looks like stacks ofcoins called granum(grana singular). The stroma is the spacesurrounding thegranum 10. Why are plants green? 11. Why are plants green?Different wavelengths of visible light are seen bythe human eye as different colors. GammaMicro- Radio X-rays UV Infraredrayswaveswaves Visible light Wavelength (nm) 12. The feathers of male cardinalsare loaded with carotenoidpigments. These pigmentsabsorb some wavelengths oflight and reflect others. Sunlight minus absorbed wavelengths or colors equals the apparent color of an object. 13. Why are plants green?Transmitted light 14. Why are plants green?Plant Cellshave GreenChloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids). 15. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED Chloroplasts absorb light energy and convert it to chemicalLight Reflected light energyAbsorbedlight Transmitted Chloroplast light 16. During fall what causes pigments to change colour? 17. Fall Colours In addition to the chlorophyll pigments, there are other pigments present. During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments (carotenoids and xantophylls) 18. Pigments Chlorophyll A is the most important photosynthetic pigment. Other pigments called antenna or accessory pigments are also present in the leaf. Chlorophyll B Carotenoids (orange / red) Xanthophylls (yellow / brown) These pigments are embedded in the membranes of the chloroplast in groups called photosystems. 19. Different pigments absorb light differently 20. Chlorophyll in the chloroplasts Chlorophyll moleculesare embedded in thethylakoid membrane Act like a lightantenna These molecules canabsorb sunlightenergy. 21. Photosystem Reaction centre(chlorophyll a & electronacceptor) Light-harvesting complex(pigment moleculesbounded to proteins) 22. Harvesting lightThere are two types ofreaction centre: Photosystem I is arranged around a chlorophyll a molecule with absorption peak of 700 nm. Photosystem II is arranged around a chlorophyll a molecule with absorption peak of 680 nm. 23. Photosynthesis occurs in 2 phases: The light reactionsconvert solar energyLight Chloroplastto chemical energyNADP Produce ATP & ADPNADPH+PCalvinLightcyclereactions The Calvin cycle makessugar from carbondioxide The ATP and NADPH areused to assemble sugarsand other organiccompounds 24. Excitation of chlorophyllin a chloroplast Loss of energy due to heat causes the photons of light to be less energetic.eExcited 2stateLess energy translates into longer wavelength.Fluorescene Heat Transition toward the red end of the visible spectrum.Light Light (fluorescence)Photon Ground state Chlorophyllmolecule (a) Absorption of a photon (b) fluorescence of isolated chlorophyll in solution 25. 1. Light Reaction (Electron Flow) Occurs in the Thylakoid membranes During the light reaction, there are two possible routes for electron flow.A. Noncyclic Electron FlowB. Cyclic Electron Flow 26. B. Noncyclic Electron Flow Occurs in the thylakoid membrane Uses PS II and PS I P680 rxn center (PSII) - chlorophyll a P700 rxn center (PS I) - chlorophyll a Uses Electron Transport Chain (ETC) Generates O2, ATP and NADPH 27. Noncyclic Photophosphorylation Photosystem II regains electrons by splitting water,leaving O2 gas as a by-product Primaryelectron acceptor Primaryelectron acceptorPhotons Energy forsynthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis 28. Two types of photosystems cooperate in the light reactionsATPmillWater-splittingNADPH-producing photosystem photosystem 29. In the light reactions, electron transport chainsgenerate ATP, NADPH, & O2 Two connected photosystems collect photons of lightand transfer the energy to chlorophyll electrons The excited electrons are passed from the primaryelectron acceptor to electron transport chains Their energy ends up in ATP and NADPH 30. B. Noncyclic Electron Flow ADP +P ATP (photophosphorylation) NADP+ + HNADPH (source of energized electrons) Oxygen comes from the splitting of H2O, not CO2H 2O 1/2 O2 + 2H+ 31. A. Cyclic Electron Flow Occurs in the thylakoid membrane. Uses Photosystem I only P700 reaction center- chlorophyll a Uses Electron Transport Chain (ETC) Generates ATP onlyADP + P ATP 32. A. Cyclic Electron FlowReaction Center => 700 nm2e- 2e-2e-2e- 33. The Hill reaction Hill placed cells of the green alga Chlorella into watercontaining the heavy isotope 18O He was able to show that the Oxigen given off inphotosynthesis was na isotope 18O which must havecome from water. 34. When Hill repeated the experiment with CO2 containing the heavy18O instead, the oxygen given off was normal 16OPhotolysisH2O + Energy O2 + 2H+ + 2e- 35. The production of ATP by chemiosmosis in photosynthesisThylakoidcompartment(high H+) LightLightThylakoidmembrane Antenna moleculesStromaELECTRON TRANSPORT(low H+)CHAINPHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE 36. Chemiosmosis powers ATP synthesis in thelight reactions The electron transport chains are arranged with thephotosystems in the thylakoid membranes and pump H+ intothe thylakoid space The flow of H+ back through the membrane is harnessedby ATP synthase to make ATP In the stroma, the H+ ions combine with NADP+ to formNADPH Video 37. Calvin Cycle Calvin Cycle (light-independent) occur in the stroma: Carbon fixation Carbon dioxide is fixed into the sugar glucose. ATP and NADPH molecules created during the lightreactions power the production of this glucose. 38. The Calvin Cycle 39. Carbon Fixation: (3) CO2 molecules enter Rubisco attaches the Co2 to RuBP The 6C product immediately splits into 2x glycerate 3-phosphate 40. Reduction 6 ATP and 6 NADPH used Some of the triose phosphatemolecule are linked to formGlucose phosphate 41. Regenerate RuBP Use 3 more ATPVideo 42. The light-independent stage CO2 combines with a five-carbon compound, ribulose biphospate (RuBP) The unstablr 6-carbon compound breaks down to form 2 molecules of 3-carbon glycerate 3-phosphate ATP is used to phosphorylate the 2 molecules of GP forming 2 molecules of glycerate biphosphate 43. The light-independent stage NADPH reduces each molecule of glycerate biphosphate to glyceraldehyde 3-phosphate (GALP) For every six molecules of GALP formed, five are used in a series of reactions to regerate RuBP. One of six GALP molecules is converted to glucose and other carbohydrates, aminoa cids and lipids 44. A Photosynthesis Road MapChloroplastLight Stroma Stack of NADP thylakoids ADP+PLight Calvinreactionscycle Sugar used for Cellular respiration Cellulose Starch Other organic compoundsVideoVideo Video 45. http://www.youtube.com/watch?v=-37Rrw1vEsw&feature=related http://www.youtube.com/watch?v=ixpNw6mx3lk&feature=related http://www.youtube.com/watch?v=yGYUnDFmJdM&feature=related http://www.youtube.com/watch?v=kzLz2EcSPnQ&feature=related http://www.youtube.com/watch?v=isyksgQPnVY&feature=related http://www.youtube.com/watch?v=mYbMP wmwx88&feature=related