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Different Stars Give off Different types of light or Electromagnetic Waves The color of plants depends on the spectrum of the star’s light, which astronomers can easily observe. (Our Sun is a type “G” star.) Wavelength Is the distance between the crests of waves Determines the type of electromagnetic energy Is the entire range of electromagnetic energy, or radiation The longer the wavelength the lower the energy associated with the wave. Light is a form of electromagnetic energy, which travels in waves When white light passes through a prism the individual wavelengths are separated out. Light travels in waves Light is a form of radiant energy Radiant energy is made of tiny packets of energy called photons The red end of the spectrum has the lowest energy (longer wavelength) while the blue end is the highest energy (shorter wavelength). The order of visible light is ROY-G-BIV This is the same order you will see in a rainbow b/c water droplets in the air act as tiny prisms Light Reflect – a small amount of light is reflected off Reflected of the leaf. Most leaves reflect Light the color green, Chloroplast which means that it absorbs all of the other colors or wavelengths. Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis) Absorbed Granum Transmittedlight – some light passes through the leaf Transmitted light Figure 10.7 Concept Map Photosynthesis includes Light independent reactions Light dependent reactions uses Light Energy Thylakoid membranes to produce ATP NADPH occurs in occur in Stroma of O2 Chloroplasts uses ATP NADPH to produce Glucose Leaf cross section Vein Mesophyll Stomata Figure 10.3 CO2 O2 Are located within the palisade layer of the leaf Stacks of membrane sacs called Thylakoids Contain pigments on the surface Pigments absorb certain wavelenghts of light A Stack of Thylakoids is called a Granum Mesophyll Chloroplast 5 µm Outer membrane Stroma Granum Intermembrane space Thylakoid Thylakoid space Inner membrane 1 µm Are molecules that absorb light Chlorophyll, a green pigment, is the primary absorber for photosynthesis There are two types of cholorophyll Chlorophyll a Chlorophyll b Carotenoids, yellow & orange pigments, are those that produce fall colors. Lots of Vitamin A for your eyes! Chlorophyll is so abundant that the other pigments are not visible so the plant is green…Then why do leaves change color in the fall? In the fall when the temperature drops plants stop making Chrlorophyll and the Carotenoids and other pigments are left over (that’s why leaves change color in the fall). The absorption spectra of three types of pigments in chloroplasts Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below. EXPERIMENT RESULTS Chlorophyll a Absorption of light by chloroplast pigments Chlorophyll b Carotenoids Wavelength of light (nm) (a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments. Figure 10.9 The action spectrum of a pigment Profiles the relative effectiveness of different wavelengths of radiation in driving photosynthesis Rate of photosynthesis (measured by O2 release) (b) Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids. The action spectrum for photosynthesis Was first demonstrated by Theodor W. Engelmann Aerobic bacteria Filament of alga 500 600 700 400 (c) Engelmann‘s experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O2 and thus photosynthesizing most. Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b. CONCLUSION photosynthesis. Light in the violet-blue and red portions of the spectrum are most effective in driving Similar- both have two peaks. For both graphs the peak is the higher in the blue end. Both have a valley in the green part of the spectrum. Different- Chlorophyll B peaks more in blue, whereas chlorophyll a has its peak to the left in violet. (they are at different wavelengths of light) (2) Any reasonable explanation accepted that connects to the data…Chlorophyll absorbs light in the red and blue ends of the light spectrum but not green. So green is reflected back to our eyes and that is what we see. (2) reasonable explanation…Reflected and/or transmitted (goes through) 1. Explain why leaves are green. Begin your explanation with white light coming from the sun and ending in your eye. (4) White Light from the sun hits leaf all wavelengths (colors) absorbed but green green reflected to our eyes X-axis: Wavelength (2) units: nanometers (1) Y -axis: % absorption (2) Line graph for carotenoids (2) Appropriate title- Absorption of carotenoids at various wavelengths in the visible light spectrum (2) Molecules that absorb specific wavelengths of light Chlorophyll absorbs reds & blues and reflects green Xanthophyll absorbs red, blues, greens & reflects yellow Carotenoids reflect orange Green pigment in plants Traps sun’s energy Sunlight energizes electron in chlorophyll What is beta carotene? Where is it found? What does it do for plants? Why is it beneficial in a human diet? (4 extra credit) Beta-carotene is one of a group of natural chemicals known as carotenes or carotenoids. Carotenes are responsible for the orange color of many fruits and vegetables such as carrots, pumpkins, and sweet potatoes. Beta carotene is converted in the body to vitamin A. It is an antioxidant, like vitamins E and C. Chlorophyll a Is the main photosynthetic pigment Chlorophyll b Is an accessory pigment CH3 in chlorophyll a CHO in chlorophyll b CH2 CH C H3C C H C C C C C N C N C Mg N C C C H C N C H3C CH3 H CH2 H H C C C O C H C CH3 CH3 Porphyrin ring: Light-absorbing “head” of molecule note magnesium atom at center C O O CH2 C C CH2 C O O CH3 CH2 Figure 10.10 Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts: H atoms not shown Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together” Photosynthesis puts together sugar molecules using water, carbon dioxide, & energy from light. Light-Dependent Reaction Light-Independent Reaction Converts light energy into chemical energy Produces simple sugars (glucose) General Equation 6 CO2 + 6 H2O C6H12O6 + 6 O2 Requires Light = Light Dependent Reaction Sun’s energy energizes an electron in chlorophyll molecule Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast When a pigment absorbs light It goes from a ground state to an excited state, which is unstable e– Excited state Heat Photon (fluorescence) Photon Figure 10.11 A Chlorophyll molecule Ground state If an isolated solution of chlorophyll is illuminated It will fluoresce, giving off light and heat Figure 10.11 B Electron from Chlorophyll is passed from protein to protein along an electron transport chain Electrons lose energy (energy changes form) Finally bonded with electron carrier called NADP+ to form NADPH or ATP Energy is stored for later use Photosystem II: Clusters of pigments boost eby absorbing light w/ wavelength of ~680 nm Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm. Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e- A mechanical analogy for the light reactions e– ATP e– e– NADPH e– e– e– Mill makes ATP e– Figure 10.14 Photosystem II Photosystem I A photosystem Is composed of a reaction center surrounded by a number of light-harvesting complexes Thylakoid Photosystem Photon Light-harvesting complexes Thylakoid membrane STROMA Primary election acceptor e– Transfer of energy Figure 10.12 Reaction center Special chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) Water Electrons from the splitting of water (photolysis) supply the chlorophyll molecules with the electrons they need The left over oxygen is given off as gas The Splitting of Water • Chloroplasts split water into – Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules Reactants: Products: Figure 10.4 12 H2O 6 CO2 C6H12O6 6 H2O 6 O2 Photolysis – Splitting of water with light energy Hydrogen ions (H+) from water are used to power ATP formation with the electrons Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production Animation – takes a min. to load…be patient Animation II – Does not take as long to load but it is not as good The light reactions and chemiosmosis: the organization of the thylakoid membrane H2O CO2 LIGHT NADP+ ADP LIGHT REACTOR CALVIN CYCLE ATP NADPH STROMA (Low H+ concentration) O2 [CH2O] (sugar) Cytochrome Photosystem II complex Photosystem I NADP+ reductase Light 2 H+ Fd 3 NADP+ + 2H+ NADPH + H+ Pq Pc 2 H2O THYLAKOID SPACE 1 (High H+ concentration) 1⁄ 2 O2 +2 H+ 2 H+ To Calvin cycle STROMA (Low H+ concentration) Thylakoid membrane ATP synthase ADP ATP P Figure 10.17 H+ Light-Dependent Pigment Chlorophyll Electron Transport Chain ATP NADPH Photolysis Chemiosmosis Converts light into chemical energy (ATP & NADPH are the chemical products). Oxygen is a by-product e– ATP e– e– NADPH e– e– e– Mill makes ATP e– Figure 10.14 Photosystem II Photosystem I Series of Proteins embedded in a membrane that transports electrons to an electron carrier Adenosine Triphosphate Stores energy in high energy bonds between phosphates Made from NADP+; electrons and hydrogen ions Made during light reaction Stores high energy electrons for use during light-Independent reaction (Calvin Cycle) The combination of moving hydrogen ions across a membrane to make ATP H2O CO2 Light NADP ADP + P LIGHT REACTIONS CALVIN CYCLE ATP NADPH Chloroplast Figure 10.5 O2 [CH2O] (sugar) LIGHT INDEPENDENT REACTION Also called the Calvin Cycle No Light Required Takes place in the stroma of the chloroplast Takes carbon dioxide & converts into sugar It is a cycle because it ends with a chemical used in the first step The Calvin Cycle begins and ends with RuBP CO2 is added to RuBP; “fixing” the CO2 in a compound One compound made along the way is PGAL PGAL can be made into sugars or RuBP Calvin Cycle uses ATP & NADPH The Calvin cycle Light H2 O CO2 Input 3 (Entering one CO2 at a time) NADP+ ADP CALVIN CYCLE LIGHT REACTION ATP Phase 1: Carbon fixation NADPH O2 Rubisco [CH2O] (sugar) 3 P 3 P P Short-lived intermediate P Ribulose bisphosphate (RuBP) P 6 3-Phosphoglycerate 6 ATP 6 ADP CALVIN CYCLE 3 ADP 3 ATP Phase 3: Regeneration of the CO2 acceptor (RuBP) 6 P 6 NADPH 6 NADPH+ 6 P P 5 (G3P) 6 P Glyceraldehyde-3-phosphate (G3P) P 1 Figure 10.18 P 1,3-Bisphoglycerate G3P (a sugar) Output Glucose and other organic compounds Phase 2: Reduction Chloroplast – Where the Magic Happens! + H2 O CO2 Energy Which splits water ATP and NADPH2 Light is Adsorbed By Chlorophyll ADP NADP Chloroplast O2 Light Reaction Calvin Cycle Used Energy and is recycled. + C6H12O6 Dark Reaction 6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O