The production of ATP AND NADPH the light reaction of photosynthesis Figure 7.9 Thylakoid compartment (high H + ) Thylakoid membrane Stroma (low H + )

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  • The production of ATP AND NADPH the light reaction of photosynthesisFigure 7.9Thylakoid compartment (high H+)Thylakoid membraneStroma (low H+)LightAntenna moleculesLightELECTRON TRANSPORT CHAINPHOTOSYSTEM IIPHOTOSYSTEM IATP SYNTHASE

  • ATP and NADPH power sugar synthesis in the Calvin cycle

    The Calvin cycle occurs in the chloroplasts stroma This is where carbon fixation takes place and sugar is manufacturedINPUTFigure 7.10AOUTPUT:CALVIN CYCLE

  • Figure 7.10BDetails of the Calvin cycleINPUT:Step Carbon fixation.In a reaction catalyzed by rubisco, 3 molecules of CO2 are fixed.11Step Energy consumption23PPP662ATP6 ADP +P6NADPH6 NADP+6PG3PStep Release of one molecule of G3P.3CALVIN CYCLE3OUTPUT:1PGlucose and other compoundsG3PStep Regeneration of RuBP.4G3P43 ADP3ATP3CO25PRuBP3-PGA

  • Step 1carbon FixationCO2 is incorporated (fixed) into a five-carbon sugar named ribulose bisphosphate (RuBP). The enzyme that does this is RuBP carboxylase or rubisco. The most abundant protein protein on Earth. The product is a six-carbon intermediate which immediately splits in half to form two molecules of 3-phosphoglycerate (3PGA).

  • Step 2Energy consumptionATP and NADPH2 (from the light reaction) are used to convert 3-phosphoglycerate (3GPA) to glyceraldehyde 3-phosphate (G3P)three-carbon carbohydrate precursor to glucose and other sugars.

  • Step 3Output of G3Poutput is one molecule of glyceraldehyde 3-phosphateFor every three molecules of CO2 that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate Used to make Glucose

  • Step 4Regeneration of RuBP ATP is used to regenerate RuBP from G3P

  • Energy cost of Calvin CycleFor each G3P synthesized, the cycle spends: 9 ATP 6 NADPH2. Both are made in the light reaction

  • http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html

  • Review: Photosynthesis uses light energy to make food moleculesA summary of the chemical processes of photo-synthesisFigure 7.11LightChloroplastPhotosystem II Electron transport chains Photosystem ICALVIN CYCLEStromaElectronsLIGHT REACTIONSCALVIN CYCLECellular respirationCelluloseStarchOther organic compounds

  • Many plants make more sugar than they needThe excess is stored in roots, tubers, and fruitsThese are a major source of food for heterotrophs

  • C4 and CAM plants have special adaptations that save waterMost plants are C3 plants, which take CO2 directly from the air and use it in the Calvin cycleIn these types of plants, stomata on the leaf surface close when the weather is hot This causes a drop in CO2 and an increase in O2 in the leaf Photorespiration may then occur No sugar or ATP

  • Photorespiration in a C3 plantCALVIN CYCLE2-C compoundFigure 7.12A

  • Some plants have special adaptations that enable them to save waterCALVIN CYCLE4-C compoundFigure 7.12BSpecial cells in C4 plantscorn and sugarcaneincorporate CO2 into a four-carbon moleculeThis molecule can then donate CO2 to the Calvin cycle3-C sugar

  • The CAM plantspineapples, most cacti, and succulentsemploy a different mechanismCALVIN CYCLE4-C compoundFigure 7.12CThey open their stomata at night and make a four-carbon compound It is used as a CO2 source by the same cell during the day3-C sugarNightDay

  • Due to the increased burning of fossil fuels, atmospheric CO2 is increasingCO2 warms Earths surface by trapping heat in the atmosphereThis is called the greenhouse effect PHOTOSYNTHESIS, SOLAR RADIATION, AND EARTHS ATMOSPHERE

  • Figure 7.13A & BSunlightATMOSPHERERadiant heat trapped by CO2 and other gases

  • Because photosynthesis removes CO2 from the atmosphere, it moderates the greenhouse effectUnfortunately, deforestation may cause a decline in global photosynthesis

  • Mario Molino received a Nobel Prize in 1995 for his work on the ozone layerHis research focuses on how certain pollutants (greenhouse gases) damage that layerFigure 7.14A

  • Figure 7.13A & BSunlightATMOSPHERERadiant heat trapped by CO2 and other gases

  • Because photosynthesis removes CO2 from the atmosphere, it moderates the greenhouse effectUnfortunately, deforestation may cause a decline in global photosynthesis

  • 7.14 Talking About Science: Mario Molina talks about Earths protective ozone layer Mario Molino received a Nobel Prize in 1995 for his work on the ozone layerHis research focuses on how certain pollutants (greenhouse gases) damage that layerFigure 7.14A

  • The O2 in the atmosphere results from photosynthesisSolar radiation converts O2 high in the atmosphere to ozone (O3)Ozone shields organisms on the Earths surface from the damaging effects of UV radiation

  • Industrial chemicals called CFCs have hastened ozone breakdown, causing dangerous thinning of the ozone layerFigure 7.14BSunlightSouthern tip of South AmericaInternational restrictions on these chemicals are allowing recoveryAntarctica

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