Learning Resource 07. The Learning Resource goal is to use the Internet and become independent of the textbook. It is a project in progress...   Ch. X
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(Source: Dr. Nilsson's old lecture notes, and Mader, S.S. 2010. Biology. Ed. 10. Used for educational purpose.Permission given in 2001 by McGraw-Hills then sales representative, Don Grainger, to use the picture online on lecture notes.)   Plants appear green because chlorophyll reflects green light.. Otherwis, plants would be black.  Photosynthesis is the process by which (green) plants, photosynthetic (green) bacteria, and photosynthetic (green) protistans use the energy from sunlight to produce sugar. The organisms capable of photosynthesizing are green, because the process takes place in association with the green pigment chlorophyll. Before we continue: Do you know the chemical reaction formula for the photosynthesis? Light energy + 6CO2 + 6H2O -----------> C6H12O6 + 6O2  Photosynthetic Organisms --- Plants are solar energy converters. Through the process of photosynthesis plants (and other "plant-like" organisms) convert solar (or light) energy into chemical energy (ATP) -- then used by photosyntesizing cells to convert carbon cioxide to chemical energy in the bonds of carbohydrates (glucose). The chemical energy in the carbohydrates of "plants" can then be used by organisms that do not photosyntesize -- like us (we eat to get energy). Organisms that photosynthesize are called autotrophs (auto as in "automatically produce their own food"). Plants, algae, some bacteria, and plantlike protista are autotrophs. Photosynthesis takes part in the green portions in plants Photosynthesis takes part in the green portions in plants, in the chloroplasts, where the membranes of thylakoids contain the green pigment chlorophyll. In the electromagnetic spectrum, only "visible light" can be used for the photosynthesis. The wavelengths of visible light differ in energy content and color. Pigments absorb wavelengths of light. Most pigments absorb only some wavelengths, while reflecting other wavelengths.
Plants are green because the two chlorophyll pigments, and b, reflects green wavelengths of light.Photosynthesis cannot take place in green light, since the light is reflected. Only if the wavelengths are absorbed will photosynthesis take place. (The figure below show at what wavelengts of light (colors) photosynthesis works. ) Photosynthesis work best under purple and blue wavelengths of light, and also under orange and red light. At these wavelengths (colors), the light is absorbed by the plant. Cartenoids, responsible for the fall coloration of leaves in some parts of the world, play an accessory role, and absorb light in the blue wavelengths.
  The Process of Photosynthesis --- The photosynthesis takes place inside organelles called chloroplasts -- inside the chloproplasts in structures called thylacoids and in the chloroplasts matrix called the stroma. Generalized Plant Cell  The overall reaction of this process can be written:Light energy + 6CO2 + 6H2O -----------> C6H12O6 + 6O2 Translated to English from the chemical language, this means that in the presence of light, six (6) molecules of carbon dioxide (from the atmosphere), plus six molecules of water (maybe from you watering the plant), produce one molecule of sugar (glucose; so the plant can grow) plus six (6) molecules of oxygen (which is released out into the atmosphere). However, since the light (e.g., sunlight or light from a lamp) doesn't really participate in the reaction -- it is just catalyzing (helping) the reaction, the light energy is often written above the chemical reaction arrow between the reactants and the products.  Light6CO2 + 6H2O -----------> C6H12O6 + 6O2  The reaction is actually more complex than it looks in the simple formula given above. It is two reactions, linked by an ATP cycle.
 The first reaction changing the light energy from the sun (or a lamp) into chemical energy (with two different processes resulting in ATP), which can be used for the second reaction. The two reactions are:1. The Light Reaction (or the Light Dependent Reaction) 2. The Calvin Cycle (or The Light Independent Reaction; sometimes also called The Dark Reaction)  In the light reaction energized electrons from water, splits and release oxygen, and ATP and electron carriers produce the energy needed to run the Calvin Cycle.
In the Calvin Cycle carbon dioxide is picked up from the atmosphere -- "fixed", through small openings called stomata (singular stoma), and carbohydrate is produced. It takes several cycles to produce one molecule of glucose. Other Types of Photosynthesis --- There are different kinds of photosynthesis variations related to the carbon dioxide entering plants through the stomata. In some plants, e.g., desert plants, the stomata is open only at night to conserve water. Carbon fixation occurs at night, and the rest of the Calvin Cycle during the day. - - - Introduction to the Atom (Khan Academy You Tube) - - -COMMENT ON THE YOUTUBE: Just wanted you to know your videos have given me spectacular insight and definetly credit you for my wonderful grades If you have problems understanding the concept of the "photosynthesis" here is an excellent YouTube video from Khan Academy, which will help you understand -- even though some of the information is beyond what is required for this class. It is 14 minutes long; I don't recommend that you try to view it from home unless you are connected via broadband. It takes too long to download via telephone modem. View it at STC instead... Sometimes YouTube videos disappear. Hopefully it will not happen often, but if it does there is nothing that can be done about it...Photosynthesis (Source: Khan Academy, You Tube. Used for educational purpose.) Photosynthesis - mr do's biology help himrdo. (2min 30sec: Crossection of a thylacoid inside a chloroplast with reactions/electron transport.) Below is a picture of a chloroplast from Mr. Do's video. Fill in the missing "chemicals": Light energy + 6CO2 + 6H2O -----------> C6H12O6 + 6O2 Plants capture solar energy and store it in carbon-based organic nutrients ("glucose") that are passed to other organisms when they feed on plants and/or on other organisms. Plants are called autotrophs because they make their own organic food. Heterotrophs are organisms that take in (e
"eat") preformed organic food. The next chapter covers cellular respiration, the process that produces ATP molecules. According to the 1st law of thermodynamics, the cell cannot create energy, but transforms (convert) energy in the glucose molecule the energy in ATP molecules. These two processes, the photosynthesis and the cellular respiration is related to the environmental problem we call Global Warming. The amount of carbon dioxide in the atmosphere is increasing in part because of fossil fuel use. Plants and plantlike organisms take in carbon dioxide when they photosynthesize. Carbon dioxide is returned to the atmosphere when plants and animals carry on cellular respiration. Energy does NOT cycle, and therefore all life is dependent on plants to capture solar energy.
The picture of a chloroplast from Mr. Do's video -- with the chemicals filled in: Light energy + 6CO2 + 6H2O -----------> C6H12O6 + 6O2 Same figure as higher up in these notes:(Source: Mader, S.S. 2010. Biology. Ed. 10. Used for educational purpose.) Scroll down for handout picture of the photosynthesis... Light energy + 6CO2 + 6H2O -----------> C6H12O6 + 6O2  Scroll down for key... 
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