Chapter 7 CAPTURING SOLAR ENERGY: PHOTOSYNTHESISPhotosynthesis vs. Cellular Respiration---Photosynthesis transforms light energy trapped by chloroplasts into chemical bond energy and stores that energy in sugar and other organic moleculesWhat type of chemical reaction is photosynthesis?PowerPoint PresentationSlide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12PhotosynthesisLight-dependent reactionsIn the light-dependent reaction: H2O + NADP+ + ADP => O2 + NADPH + ATPLight-independent reactionsIn the light-independent reaction: CO2 + ATP + NADPH + H2O => C6H12O6 + ADP + NADP+Slide 18>The nature of sunlight Light is electromagnetic energy Light energy has both wavelike and particle-like propertiesWavelike properties -Electromagnetic energy travels in waves. -Wavelength-shorter wavelength light has higher energy, while longer wavelength light has lower energy. -Electromagnetic spectrum (gamma rays) 10-3 nm to 103 m radio waves) -Visible light 400 nm to 750 nmLight as wavesParticle-like properties -Electromagnetic energy also travels in particles. -discrete particles called photonsPhotosynthetic pigments ---Pigments are substances that absorb visible lightWhy do leaves change colors in the Fall?Slide 25>Photosystems are the assemblies which turn light energy into chemical energy in the thylakoid membranes. Chlorophyll, proteins, and the accessory pigments are arranged into a photosystemSlide 27Light-dependent reactionSlide 29What is the purpose of having two photosystems in the light-dependent reactions?When less water is available during a drought, why is the rate of photosynthesis in plants reduced?Slide 32Slide 33---Chemiosmosis is the coupling of electron flow down an electron transport chain to ATP production by creation of a gradient across the membrane.PS-II generates ATP by chemiosmosis PS-I generates NADPHSlide 36---Calvin-Benson cycle (a.k.a. The C3 cycle) is the cycle of reactions in photosynthesis in which atmospheric carbon CO2 is fixed (carbon fixation) using ATP and NADPHThe Calvin-Benson Cycle is divided into 3 phasesC3 CycleSlide 40Slide 41In the Calvin cycle, where do the carbons used to synthesize glucose originate?Slide 43How are the light-dependent reactions and the Calvin cycle related?What is responsible for the beautiful shades of red, orange, and gold in autumn leaves?Chapter 7CAPTURING SOLAR ENERGY: PHOTOSYNTHESISChloroplasts are the site of photosynthesis in plantsPhotosynthesis vs. Cellular Respiration•Photosynthesis is the opposite of cellular respiration.•During photosynthesis, glucose and other energy-rich molecules are made through a process that requires energy from the sun.•During cellular respiration, energy is obtained from glucose and other energy-rich molecules.---Photosynthesis transforms light energy trapped by chloroplasts into chemical bond energy and stores that energy in sugar and other organic molecules•Synthesis of energy-rich organic molecules (glucose) from energy-poor molecules (CO2 and H2O)•Uses CO2 as a carbon source and sunlight-energy as the energy source.•Directly or indirectly supplies energy to most living organisms.What type of chemical reaction is photosynthesis?•Covalent•Endergonic•Exergonic•Ioniccellularrespirationphotosynthesis(chloroplast)H2OCO2sugarATPO2(mitochondrion)Leaves are the major organs of photosynthesisFig. 7.1Chlorophyll is the green pigment that gives a leaf its color. Chlorophyll is also responsible for the absorption of the light energy that drives photosynthesisFig. 7.1amesophyllcellsChloroplasts are primarily in cells of mesophyll (in the leaf interior)Fig. 7.1bmesophyllcellsstomaCO2 and H2O enter the leaf through pores called stomata or stomaFig. 7.1bmesophyllcellsvascular bundle(vein)stomaWater is absorbed by the roots and transported to the leaves through the vascular bundles.Fig. 7.1bthylakoidStroma (fluid)Chloroplasts contain the thylakoids and the stroma Fig. 7.1dthylakoidstromaThylakoids are flattened membranous sacs inside the chloroplast.Chlorophyll is located in the thylakoid membrane.Fig. 7.1dPhotosynthesis•Consists of 2 different reactions: one that is light-dependent, and one that is light-independent. •The 2 different reactions occur in different regions of the chloroplast.Light-dependent reactions•Sunlight is converted into chemical energy that is stored in energy-carrier molecules called ATP and NADPH. •Oxygen is released as a by-product.•Occurs in the thylakoid membranes.In the light-dependent reaction:H2O + NADP+ + ADP => O2 + NADPH + ATPLight-independent reactions•The chemical energy in the carrier molecules (ATP and NADPH) is used to make glucose, and other organic molecules.•Takes place in the stroma, which is the fluid-filled space outside the thylakoids within the chloroplast.In the light-independent reaction:CO2 + ATP + NADPH + H2O => C6H12O6 + ADP + NADP+LIGHT-DEPENDENTREACTIONS(thylakoids)LIGHT-INDEPENDENTREACTIONS(stroma)depletedcarriers(ADP, NADP+)H2O O2CO2 + H2Oglucoseenergizedcarriers(ATP, NADPH)>The nature of sunlightLight is electromagnetic energyLight energy has both wavelike and particle-like propertiesWavelike properties-Electromagnetic energy travels in waves.-Wavelength-shorter wavelength light has higher energy, while longer wavelength light has lower energy. -Electromagnetic spectrum (gamma rays) 10-3 nm to 103 m radio waves) -Visible light 400 nm to 750 nmWavelength (nanometers)Visible light400 450500550 600 650700750Gamma rays X-rays UV InfraredMicro-wavesRadiowavesLight as wavesFig. 7.4Particle-like properties-Electromagnetic energy also travels in particles.-discrete particles called photonsPhotosynthetic pigments---Pigments are substances that absorb visible light-Chlorophyll is the pigment which is the key light-capturing molecule in thylakoid membranes.-Other pigments (carotenoids and phycocyanins) are called accessory pigmentsWhy do leaves change colors in the Fall?•During the Spring and Summer, Chlorophyll a and b are the primary pigments being used while photosynthesis levels are high.•During the Fall, many plants go into a form of ‘hibernation’ where photosynthesis levels are decreased.•Chlorophyll a and b are broken down, and accessory pigments are the dominant pigment.Fig. 7.5>Photosystems are the assemblies which turn light energy into chemical energy in the thylakoid membranes.Chlorophyll, proteins, and the accessory pigments are arranged into a photosystemthylakoidsPS IIchloroplastPS IETCETCreaction
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