Photosynthesis lab report

Photosynthesis lab report - The Effect of Differing Light...

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The Effect of Differing Light Intensity on Photosynthesis Section 401 TA: Eric Fransisco Peter Rehder June 23, 2010 Pledge: I pledge that no unauthorized assistance has been given or received in the completion of this work. Experiments described were performed by me and/or my lab group and this write-up is entirely my own creative work. Signature ___________________ Introduction The presence of light is essential to the process of photosynthesis, as demonstrated by the chemical reaction: 6CO 2 + 6H 2 O + light C 6 H 12 O 6 + 6O 2 (DeSaix and Stegenga 2009). In plant cells, photosynthesis takes place in the chloroplasts and is separated into two reactions, the light- dependent reaction (Hill reaction) and the light-independent reaction (Calvin-Benson Cycle)
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(DeSaix and Stegenga 2009). The Hill reaction, which is the focus of this report, takes place in the thylakoid membrane of the chloroplasts. Through a series of oxidation-reduction reactions, water and NADP + react to form NADPH, hydrogen ions, and gaseous oxygen. This process is illustrated by the chemical reaction: 2H 2 O +2NADP + 2NADPH + 2H + + O 2 . The oxygen is left as an end product while the other products of the Hill reaction become reactants for the light- independent reaction, which produces glucose. As an overall synthesis of the process, light combines with water and carbon dioxide to produce glucose and oxygen. These products then fuel cellular respiration, which yields energy in the form of ATP. Plants can then use this energy for cellular processes like protein synthesis, reproduction, and growth. In addition, other organisms that consume these plants get energy from the ATP they produce. Without light as a reactant in the process of photosynthesis, plants would be unable to produce ATP and fuel their own processes or the processes of other organisms. A factor that poses a question in the process of photosynthesis is the intensity of the light that is involved in the reaction. Does the intensity of the light shining on the plant change the amount of oxygen and glucose produced by photosynthesis? The brightness of the light may influence the speed of the photosynthesis reaction and result in a higher product yield. This light intensity can be described by lumens (lm), a measure of the amount of light emitted by a light source, such as an incandescent light bulb (EFI 2008). Wattage of various light bulbs can be converted to lumens to demonstrate the intensity of light being used by plants for photosynthesis. In order to test the effects of differing light intensity on photosynthesis, incandescent light bulbs of various lumens can be used to fuel photosynthesis in the chloroplasts of spinach leaves. The chemical DPIP can be used to indicate that photosynthesis is taking place in the
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chloroplasts. DPIP is blue, but as photosynthesis takes place, it is reduced to DPIPH 2 and changes to a clear substance. Because DPIP is similar to NADPH, it can replace NADPH as a part of the Hill reaction in the laboratory. The replacement results in this chemical equation:
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This note was uploaded on 10/07/2011 for the course BIOL 101L taught by Professor Stengaga during the Summer '08 term at UNC.

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Photosynthesis lab report - The Effect of Differing Light...

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