Presentation on theme: "Relate the structure of chloroplasts to the events in photosynthesis"— Presentation transcript:
1 Relate the structure of chloroplasts to the events in photosynthesis Section ObjectivesRelate the structure of chloroplasts to the events in photosynthesisDescribe light-dependent reactions.Explain the reactions and products of the light-independent Calvin cycle.
3 Trapping Energy from Sunlight The process that uses the sun’s energy to make simple sugars is called photosynthesis.
4 AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and waterPHOTOSYNTHESIS
5 Plants are energy producers Like animals, plants need energy to liveunlike animals, plants don’t need to eat food to make that energyPlants make both FOOD & ENERGYanimals are heterotrophs(consumers)plants are autotrophs (producers)
6 How do plants make energy & food? Plants use the energy from the sunto make ATP energyto make sugarsglucose, sucrose, cellulose, starch, & moresunATPsugars
7 Building plants from sunlight & air Photosynthesis2 separate processesENERGY building reactionscollect sun energyuse it to make ATPSUGAR building reactionstake the ATP energycollect CO2 from air & H2O from grounduse all to build sugarsATPH2O+CO2sugarscarbon dioxideCO2waterH2OsugarsC6H12O6+
8 What do plants need to grow? The “factory” for trapping energy & making sugarschloroplastFuelssunlightcarbon dioxidewaterThe Products- Oxygen & GlucoseThe HelpersEnzymessunCO2O2enzymessugarsH2O
9 So what does a plant need? Bring InlightCO2H2OLet OutO2Move Aroundsugarsleavesshootroots6CO26H2OC6H12O66O2lightenergy+
10 Photosynthesis ATP ADP ENERGY building reactions sunPhotosynthesisENERGY building reactionsADPATPSUGAR building reactionsused immediately to synthesize sugarsH2OsugarCO2
11 Chloroplasts absorb sunlight & CO2 Leaf Leaves CO2 Chloroplasts in cellChloroplastChloroplastChloroplastscontainChlorophyllmake ENERGY & SUGAR
12 Stomates & Guard Cells in the leaf Function of stomatesCO2 inO2 outH2O outgets to leaves for photosynthesisFunction of guard cellsopen & close stomatesguard cellstomate
13 An overview of photosynthesis ChloroplastLightCO2H2ONADP+ADP +PLIGHT REACTIONS (in granaCALVIN CYCLE (in stromaATPNADPHO2O2Sugar
14 Trapping Energy from Sunlight Photosynthesis happens in two phases.The light-dependent reactions convert light energy into chemical energy. (ATP)2. The molecules of ATP produced in the light-dependent reactions are then used to fuel the Calvin Cycle or light-independent reactions that produce simple sugars.The general equation for photosynthesis is written as CO2 + 6H2O→C6H12O6 + 6O2
15 THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Visible radiation drives the light reactionsCertain wavelengths of visible light drive the light reactions of photosynthesisX-raysMicro- wavesRadiowavesGamma raysUVInfraredVisible lightWavelength (nm)
16 pigments in the chloroplast To trap the energy in the sun’s light, the thylakoid membranes contain pigments, molecules that absorb specific wavelengths of sunlight.Wavelengths that are NOT absorbed are reflected (bounce off) or transmitted (pass through)So the material in which the pigment is found appears to be the color of the wavelengths that are NOT absorbedPhotosynthetic pigments: can absorb light energy & make it available for conversion to chemical energy.LightReflected lightChloroplastAbsorbed light
17 pigments in the chloroplast Chlorophyll a: most common pigment in chloroplast (absorbs blue &red light and reflects green light thus giving the chloroplast a green color)(chloro = green phylla + leaf)Accessory pigments: additional pigments that absorb different wavelengths (carotene, chlorophyll b, & xanthophyll)
19 Light-Dependent Reactions absorption of light energy by chlorophyll As sunlight strikes the chlorophyll molecules in a photosystem of the thylakoid membrane, the energy in the light is transferred to electrons.These highly energized, or excited, electrons are passed from chlorophyll to an electron transport chain, a series of proteins embedded in the thylakoid membrane.At each step along the transport chain, the electrons lose energy.
20 Energy from the energized electrons pump H+ ions and change NAPD+ to NADPH.The H+ ions move from high to low and turnthe ATP synthase and change ADP + P to ATPEnergized electronsOxygenby-productPhotolysis
21 Light-Dependent Reactions Chemiosmosis: This “lost” energy can be used to form ATP from ADP, or to pump hydrogen ions into the center of the thylakoid disc..
22 Light-Dependent Reactions The electrons are transferred to the stroma of the chloroplast. To do this, an electron carrier molecule called NADP is used.NADP can combine with two excited electrons and a hydrogen ion (H+) to become NADPH.NADPH will play an important role in the light-independent reactions.
23 Restoring electronsTo replace the lost electrons, molecules of water are split in the first photosystem. This reaction is called photolysis.The O2 liberated by photosynthesis is made from the oxygen in waterChlorophyllO2 + 2H+22e-H2OH2O ®2H+ +O2 + 2e-
24 Restoring electronsThe oxygen produced by photolysis is released into the air and supplies the oxygen we breathe.The electrons are returned to chlorophyll.The hydrogen ions are pumped into the thylakoid, where they accumulate in high concentration.
25 Light Dependent Reactions: Summary Absorptions of light energy by chlorophyll-takes place in thylakoid1. Split water molecule (PHOTOLYSIS) Oxygen combines with other oxygen to produce O2 which is given off as a by-product2. Hydrogen produced by splitting of water is attached to hydrogen carrier NADP -> NADPH (energy in this molecule)3. Then energy from “excited electrons”is used to take ADP + P ->ATP
26 Light Independent Reactions or The Calvin Cycle CO2 put into organic molecules called Carbon fixationDoes not require light but must have ATP and NADPH which are produced by light dependent reactionsCalled Calvin Cycle (Melvin Calvin won Nobel prize in chemistry)Takes place in stroma of chloroplast
27 Light Independent Reactions or The Calvin Cycle The Calvin cycle constructs G3P (a sugar) usingcarbon from atmospheric CO2electrons and H+ from NADPHenergy from ATPEnergy-rich sugar (G3P) is then converted into glucoseINPUTCALVIN CYCLEOUTPUT:
28 So what does a plant need? Bring InlightCO2H2OLet OutO2Move Aroundsugarsleavesshootroots6CO26H2OC6H12O66O2lightenergy+
29 An overview of photosynthesis ChloroplastLightCO2H2ONADP+ADP +PLIGHT REACTIONS (in granaCALVIN CYCLE (in stromaATPNADPHO2Sugar
30 Factors Affecting Rate of Photosynthesis Temperature: increases rate up to a certain pointLight Intensity: increases rate up to a certain pointCO2 level: Increases rate up to a certain pointWater: decrease water, decrease photosynthesisMinerals; Ex. Magnesium, Nitrogen