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Jan Baptisa van Helmont (1648) "...I took an earthenware vessel, placed in it 200 pounds of soil dried in an oven, soaked this with rainwater, and planted in it a willow branch weighing 5 pounds. At the end of five years, the tree grown from it weighed 169 pounds and about 3 ounces. Now, the earthenware vessel was always moistened (when necessary) only with rainwater or distilled water, and it was large enough and embedded in the ground, and, lest dust flying be mixed with the soil, an iron plate coated with tin and pierced by many holes covered the rim of the vessel. I did not compute the weight of the fallen leaves of the four autumns. Finally, I dried the soil in the vessel again, and the same 200 pounds were found, less about 2 ounces. Therefore 169 pounds of wood, bark, and root had arisen from water only.” 6CO2 + 6H2O + Energy C6H12O6 + 6O2 Glucose provides the energy and carbon needed to synthesize other plant material. 1 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Jan Baptisa van Helmont (1648) "...I took an earthenware vessel, placed in it 200 pounds of soil dried in an oven, soaked this with rainwater, and planted in it a willow branch weighing 5 pounds. At the end of five years, the tree grown from it weighed 169 pounds and about 3 ounces. Now, the earthenware vessel was always moistened (when necessary) only with rainwater or distilled water, and it was large enough and embedded in the ground, and, lest dust flying be mixed with the soil, an iron plate coated with tin and pierced by many holes covered the rim of the vessel. I did not compute the weight of the fallen leaves of the four autumns. Finally, I dried the soil in the vessel again, and the same 200 pounds were found, less about 2 ounces. Therefore 169 pounds of wood, bark, and root had arisen from water only.” 6CO2 + 6H2O + Energy C6H12O6 + 6O2 As can be seen from the equation for photosynthesis, the wood, bark, and root arose from water and carbon dioxide. 2 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Photosynthesis 3 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Before you start… 4 There are 83 slides in this presentation. Some of the slide navigation functions require full screen mode. Select “Browse” or “View” from the menu above, then select “Full Screen”. Powerpoint Version: Use the arrow keys ( or ) to advance the slides or go backwards. The left mouse button also advances slides. You can click anywhere on the screen. If you know the slide number, you can enter the number and press Enter to go directly to that slide. The slide number is at the bottom left of most slides. Press “Esc” to end the program. Internet Explorer Version: Click the slide name at the left side of the screen or use the arrow buttons at the bottom of the screen on either side of the slide counter. A menu appears at the bottom of most of the slides. You can use this to go to the topics shown. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light travels in waves. The color of light is determined by its wavelength. The red light shown below has a wavelength of 700 nm. Wavelength 700 nm Red 470 nm Notice that blue light has a shorter wavelength. Blue Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Electromagnetic Spectrum Visible light is only a part of the electromagnetic spectrum. nanometers 10-5 10-3 Gamma rays 103 1 X-rays UV 106 Infrared 1m Microwaves 103 m Radio waves Visible light 7 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Electromagnetic Spectrum The numbers on this chart are wavelength. nanometers 10-5 10-3 Gamma rays 103 1 X-rays UV 106 Infrared 1m Microwaves 103 m Radio waves Visible light 8 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Electromagnetic Spectrum nanometers 10-5 10-3 Gamma rays 103 1 X-rays UV 106 Infrared 1m Microwaves 103 m Radio waves The spectrum shown below fits into the small space shown on the line. Visible light 9 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Photosynthetic Pigments Light behaves as if it is composed of units or packets called photons. Plants have pigment molecules that contain atoms that become energized when they are struck by photons of light. Energized electrons move further from the nucleus. 11 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Photosynthetic Pigments Heat or light The energized molecule can transfer the energy to another atom or molecule or release it in the form of heat or light. 12 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Photosynthetic Pigments Heat or light When the energy is released, the electron returns to a location closer to the nucleus. 13 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return What color is best? In this experiment, a prism is used to produce a gradient of light that ranges from red to blue. The large cell is a photosynthetic alga called Spirogyra seen magnified under a microscope. The spiral-shaped green structure is its chloroplast. The bacteria (represented by dots) are aerobic, that is, they require oxygen. The slide was initially prepared so that there was no oxygen present in the water surrounding the alga. Photosynthesis produces oxygen and the bacteria congregate in areas where the most oxygen is produced, thus, where the rate of photosynthesis is highest. Blue and red light therefore produce the highest rate of photosynthesis. Bacteria Chloroplast of Spirogyra Colors produced by a prism Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Absorption Spectrum Chlorophyll a absorption Chlorophyll b This graph shows the color of light absorbed by three different kinds of photosynthetic pigments. Notice that they do not absorb light that is in the green to yellow range. Carotenoids 400 500 600 Wavelength Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | 700 Return Two Kinds of Reactions The reactions of photosynthesis can be divided into two main categories: » The light reactions require light. » The light-independent reactions occur either in the light or in the dark. As you view the rest of these slides, keep in mind that the “goal” of photosynthesis is to synthesize glucose. » Carbon dioxide is reduced to glucose (see equation below). [Be sure that you know what is meant by “reduced” before you go on.] » The electrons needed for this reduction come from water. » The energy needed for this reduction comes from light. » The equation is: Energy + 6CO2 + 6H2O C6H12O6 + 6O2 17 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Light Reactions light light reactions ATP NADPH During photosynthesis, CO2 will be reduced (gain electrons) to form glucose. The electrons needed to reduce CO2 are temporarily carried by NADPH. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return H2O light O2 Light Reactions light reactions ATP NADPH Recall that hydrogen atoms can be used to carry electrons. NADPH gets its electrons from water. The oxygen is not used. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return H2O light Light-Independent Reactions light reactions ATP C02 O2 NADPH light-independent reactions (Calvin cycle) C6H12O6 The reduction of CO2 to glucose occurs in the light-independent reactions. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return H2O O2 Summary of Photosynthesis light light reactions ATP C02 This slide summarizes photosynthesis. 6CO2 + 6H2O + E C6H12O6 + 6O2 NADPH light-independent reactions (Calvin cycle) ADP NADP+ C6H12O6 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Elodea leaf X 400 The small green structures within the cells of this plant are chloroplasts. 23 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Chloroplast Structure In order to understand the reactions of photosynthesis, it will be helpful to review the structure of a chloroplast. It contains diskshaped structures called thylakoids. The area outside the disks is called the stroma. Stroma Double membrane Thylakoids 24 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return H2O Summary of Photosynthesis light light reactions ATP C02 The next several slides will examine the light reactions of photosynthesis. O2 NADPH light-independent reactions (Calvin cycle) ADP NADP+ C6H12O6 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return This drawing shows a magnified view of a part of a thylakoid. The green area is the thylakoid and the blue area is the stroma of the chloroplast. Photosynthetic pigments embedded within the membrane form a unit called an antenna. Antenna Stroma Thylakoid membrane Antenna Photosynthetic pigments such as chlorophyll A, chlorophyll B and carotinoids. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light energy A pigment molecule within the antenna absorbs a photon of light energy. The energy from that pigment molecule is passed to neighboring pigment molecules and eventually makes its way to pigment molecule called the reaction center. When the reaction center molecule becomes excited (energized), it loses an electron to an electron acceptor. Thylakoid membrane Reaction Center, Electron Acceptor Electron acceptor Reaction center Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light energy As a result of gaining an electron (reduction), the electron acceptor becomes a high-energy molecule. Remember - its energy came from light. To understand this transfer of energy, recall that oxidation is the loss of an electron and the loss of energy. Reduction is the gain of an electron and energy. Energy is transferred with the electron. Thylakoid membrane Reaction Center, Electron Acceptor Electron acceptor Reaction center Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return The antenna and electron acceptor are called a photosystem. There are two kinds of photosystems in plants called photosystem I and photosystem II. Photosystem I is sometimes called P700 and photosystem II is sometimes P680. The 680 and 700 designations refer to the wavelength of light that they absorb best. Photosystem Antenna Thylakoid membrane Antenna, Photosystem Electron acceptor Reaction center Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return In the diagrams that follow, the antenna will be drawn as a single green circle and the electron acceptor as a single red circle. Photosystem Antenna Thylakoid membrane Antenna, Photosystem Electron acceptor Reaction center Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast Electron Transport System Photosystem II Photosystem I The three blue circles represent the electron transport system. They are proteins embedded within the thylakoid membrane. The first protein receives the electron (and energy) from the electron acceptor. Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast Electron Transport System H+ H+ H+ H+ H+ H+ H+ H+ As a result of gaining an electron (reduction), the first carrier of the electron transport system gains energy. It uses some of the energy to pump H+ into the thylakoid. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ + H Electron Transport System H+ H+ H+ H+ H+ The carrier then passes the electron to the next carrier. Because it used some energy to pump H+, it has less energy (reducing capability) to pass to the next H+ pump. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ H+ H+ Electron Transport System This carrier uses some of the remainder of the energy to pump more H+ into the thylakoid. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ H+ H+ Electron Transport System The electron is passed to the next carrier which also pumps H+. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ H+ H+ Electron Transport System The electron transport system functions to create a concentration gradient of H+inside the thylakoid. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast The concentration gradient of H+ is used to synthesize ATP. ATP is produced from ADP and Pi when hydrogen ions pass out of the thylakoid through ATP synthase. H+ H+ H+ H+ H+ H+ H+ Photophosphorylation ATP ADP + Pi H+ Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast This method of synthesizing ATP by using a H+ gradient in the thylakoid is called photophosphorylation. H+ H+ H+ H+ H+ H+ H+ ATP Photophosphorylation ADP + Pi H+ Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ H+ Photosystem I ATP ADP + Pi H+ At this point, the electron has little reducing capability (little energy is left). It is passed to the P700 antenna. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ ATP H+ P700 Antenna ADP + Pi H+ A pigment molecule in the P700 antenna absorbs a photon of solar energy. The energy from that molecule is passed to neighboring molecules within the antenna. The energy is eventually passed to the reaction center of this antenna. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast H+ H+ H+ H+ H+ H+ H+ Electron Acceptor ATP ADP + Pi H+ As a result of being energized, the P700 reaction center loses the electron to an electron acceptor. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast NADP+ + H+ NADPH H+ H+ H+ H+ H+ H+ H+ NADP+ ATP ADP + Pi H+ The acceptor passes it to NADP+, which becomes reduced to NADPH. According to the following equation, NADP+ has the capacity to carry two electrons. NADP+ + 2e- + H+ NADPH Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast NADP+ + H+ NADPH H+ H+ H+ H+ H+ H+ H+ ATP ADP + Pi Splitting H2O H+ The electron that was initially lost by photosystem II (P680) must be replaced. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast NADP+ + H+ NADPH H+ H+ H+ H+ H+ H+ H+ H2O2e- + 2H+ + ½ O2 Splitting H2O ATP ADP + Pi H+ A hydrogen atom contains one electron (e-) and one proton (H+). The two hydrogen atoms in a water molecule can therefore be used to produce 2e- and 2H+. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return e- light acceptor e- acceptor NADPH NADP+ ATP electron transport system This diagram traces the path followed by an electron during the light reactions. The path is indicated by red arrows and letters. The highenergy parts of the pathway are drawn near the top of the diagram. P700 antenna complex Summary of Light Reactions P680 antenna complex H2O 2e- + 2H+ + O Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast NADP+ + H+ CO2 NADPH H+ H+ H+ H+ H+ H2O2e- + 2H+ + ½ O2 H+ H+ Calvin Cycle Calvin Cycle ATP ADP + Pi H+ glucose The next several slides show how the products of the light reactions (ATP and NADPH) are used to reduce CO2 to carbohydrate in the Calvin cycle. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Light Energy Chloroplast NADP+ + H+ CO2 NADPH H+ H+ H+ H+ H+ H+ H+ H2O2e- + 2H+ + ½ O2 Calvin Cycle Calvin Cycle ATP ADP + Pi H+ glucose The reactions of the Calvin cycle occur in the stroma of the chloroplast. Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return H2O Light Energy O2 Chloroplast NADP+ + H+ light Summary of Photosynthesis NADPH H+ H+ + H H+ H+ H + H2O2e- + 2H+ + ½ O2 H+ ATP ADP + Pi H+ Thylakoids light reactions Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return ATP C02 NADPH ADP NADP+ light-independent reactions (Calvin cycle) C6H12O6 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return CO2 Fixation CO2 fixation refers to bonding CO2 to an organic molecule to make a larger molecule. C5 + CO2 C6 “C5” is an abbreviation that means that this molecule has 5 carbon atoms. The oxygen and hydrogen atoms are not written. 53 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return CO2 Fixation 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) The enzyme that catalyzes this reaction is ribulose biphosphate carboxylase (rubisco). 6 C-C-C-C-C CO2 fixation refers to bonding CO2 to an organic molecule to make a larger molecule. Each CO2 is bonded to ribulose biphosphate (RuBP). C5 + CO2 C6 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return C3 Photosynthesis – Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C Each of these 6-carbon compounds splits to form two 3-carbon compounds called phosphoglycerate. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C PGAL 12 C-C-C The two molecules of PGA are reduced to form PGAL (phosphoglyceraldehyde). Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C PGAL 12 C-C-C 12 ATP 12 ADP + P 12 NADPH 12 NADP+ Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C 6 ADP + P Two of the PGAL are used6toATP form glucose phosphate, then glucose. 10 C-C-C PGAL 12 C-C-C 12 ATP 12 ADP + P 12 NADPH C-C-C-C-C-C Glucose 12 NADP+ Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C 6 ADP + P The remaining 10 PGAL are rearranged to form 6 RuBP. 6 ATP 10 C-C-C PGAL 12 C-C-C 12 ATP 12 ADP + P 12 NADPH C-C-C-C-C-C Glucose 12 NADP+ Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Calvin Cycle 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C PGA 12 C-C-C 6 ADP + P 6 ATP This process requires energy in the form of ATP. 10 C-C-C PGAL 12 C-C-C 12 ATP 12 ADP + P 12 NADPH C-C-C-C-C-C Glucose 12 NADP+ Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return H2O Light Energy Chloroplast Summary of Photosynthesis NADP+ + H+ light O2 NADPH H+ H+ + H H+ H+ H + Light reactions ATP H+ H2O2e- + 2H+ + ½ O2 ADP + Pi H+ Thylakoids Stroma Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return ATP NADPH ADP NADP+ 6 CO2 C02 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) 6 C-C-C-C-C RuBP 6 ADP + P 6 ATP 10 C-C-C PGAL 12 C-C-C PGA 12 C-C-C 12 ATP 12 ADP + P 12 NADPH C-C-C-C-C-C Glucose Light-independent reactions 12 NADP+ C6H12O6 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return End of Part 1 Please go back and review these slides and the information on photosynthesis before continuing. When you are ready to resume, select “Photorespiration” on the menu. 62 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return CO2 Fixation 6 CO2 6 C-C-C-C-C-C RuBP Carboxylase (rubisco) RuBP 6 C-C-C-C-C 12 C-C-C 10 C-C-C 12 C-C-C C-C-C-C-C-C Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Cross Section of a C3 Leaf Stomata (singular stoma) are microscopic openings on the undersurface of leaves that allow gas exchange and water evaporation from inside the leaf. Because dehydration can be a serious problem, the stomata close when the plant is under water stress. When closed, CO2 needed for the Calvin cycle cannot enter. mesophyll cells stoma vein bundle-sheath cells 65 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return If CO2 is low 6 CO2 CO2 O2 6 C-C-C-C-C-C RUBISCO RuBP 6 C-C-C-C-C When the concentration of CO2 is low (red above), oxygen will bind to the active site of RUBISCO. When oxygen is bound to RUBISCO, RuBP is broken down and CO2 is released. This wastes energy and is of no use to the plant. It is called photorespiration because oxygen is taken up and CO2 is released. Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Cross Section of a C3 Leaf Photosynthesis occurs within the mesophyll cells in C3 plants, which form a dense layer on the upper surface of the leaf and a spongy layer on the lower surface. Bundle-sheath cells surrounding the veins are not photosynthetic. mesophyll cells stoma vein bundle-sheath cells 67 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Cross Section of a C4 Leaf bundle-sheath cells vein mesophyll cells stoma 69 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return CO2 Fixation in C4 Plants CO2 CO2 fixation occurs in mesophyll cells C3 C4 mesophyll cells Calvin cycle 70 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return CO2 Fixation in C4 Plants CO2 C3 CO2 fixation occurs in mesophyll cells Calvin cycle occurs in bundle sheath cells C3 C4 CO2 Calvin cycle 71 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review Exercises 72 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – ATP Identify components A through D. A ADP + Pi ATP Energy B C D 73 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – NADPH NADP+ NADPH + H+ Energy + 2H A B C D 74 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Summary of Photosynthesis H I Identify: A light reactions ADP + Pi ATP Calvin cycle CO2 glucose phosphate light NADP+ NADPH oxygen water D B F C E J G Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Review – Chloroplast Structure Where do the light reactions occur? Where do the light-independent reactions occur? light H2O 2H+ 2e- + O C02 light reactions ADP ATP NADPH NADP+ light-independent reactions (Calvin cycle) C-C-C-C-C-C Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Review – Calvin Cycle How many carbon atoms? 6A 6C 12 D 6B 10 F 12 E G Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C4 plants | Review | Return Review – Calvin Cycle Identify each component. 6A 6C 12 D 6B 6L 12 H 6M 10 F 12 I 12 E 12 K 12 J G 78 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Inputs and Products Fill in the Boxes below. Light Reactions Light-Independent Reactions Inputs Produced 79 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Inputs and Products Fill in the Boxes below. Light Reactions Inputs Light-Independent Reactions light, ADP, NADP+, H2O Produced 80 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Inputs and Products Fill in the Boxes below. Light Reactions Inputs light, ADP, NADP+, H2O Produced ATP, NADPH, O2 , H + Light-Independent Reactions 81 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Inputs and Products Fill in the Boxes below. Light Reactions Inputs light, ADP, NADP+, H2O Produced ATP, NADPH, O2 , H + Light-Independent Reactions ATP, NADPH, CO2 82 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return Review – Inputs and Products Fill in the Boxes below. Light Reactions Light-Independent Reactions ATP, NADPH, CO2 Inputs light, ADP, NADP+, H2O Produced ATP, NADPH, O2 , H + glucose, ADP, NADP+ 83 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return The End 84 Light | Pigments | Overview | Chloroplast | Photosystem II | Electron Transport System | Photosystem I | Calvin Cycle | Photorespiration | C 4 plants | Review | Return