6 Photosynthesis - Katherine Rumfield BIOL 111 560 18 Oct...

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Katherine Rumfield BIOL 111 – 560 18 Oct 2016 The Effects of Light on Photosynthesis Abstract: Photosynthesis is dependent on several factors, including light intensity and the wavelength of the light to which it is exposed. Photosynthetic pigments play a large role in whether or not a plant will photosynthesize under specific wavelengths. Through the use of a spectrophotometer, it was discovered that absorption decreased at higher rates under more intense light sources, thus photosynthesis increased. With the help of light boxes, it was revealed that plants photosynthesize at higher rates under white light. By using silica gel chromatography, it was found that there were seven different pigments in the chloroplasts of the spinach. Four of these pigments were then tested at varying wavelengths in a spectrophotometer to create an absorption spectrum that showed that different pigments absorb different amounts of light at different wavelengths.Introduction:Photosynthesis is the process that takes light energy from the sun and converts it into chemical energy. It could be considered one of the most important biochemical processes on our planet, as it provides the main source of chemical energy for the biosphere. In eukaryotes such asalgae and plants, this process takes place within the chloroplasts in the thylakoid membranes. These photosynthetic cells convert carbon dioxide into food for the cell using light energy, while water molecules are split to produce oxygen and the electrons used to aid in the transformation ofcarbon dioxide to glucose. The focus of the first experiment was to see if varying light intensities had any effect on photosynthesis. Within the thylakoid membranes of plants, there are two photosystems that use light to breakdown molecules and fuel the electron transport chain. Photosystem II absorbs light energy that excites the electrons found in chlorophyll (a major photosynthetic pigment), which are passed through the electron transport chain, and then to photosystem I. Here, solar energy is again absorbed, exciting electrons that are passed onto a second electron transport chain that ultimately yields NADPH to be used in the Calvin cycle. The effect of light intensity on photosynthesis can be tested by replacing the usual NADPH with DPIP, which changes from a blue color to clear as it is chemically reduced. As more DPIP is reduced, there will be a larger absorbance reading calculated by the spectrophotometer. It was hypothesized that an increase in the intensity of light would produce an increase in the rate of photosynthesis.White light holds all the wavelengths of light found on the visible spectrum. The specific colors that we see are a result of pigments that selectively absorb certain wavelengths of light, while reflecting others. These reflected, or transmitted, wavelengths produce the shades that we associate with the color of an object. The goal of the second experiment was to create an action

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