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photosynthesislabreport - Doorhy 1 Colleen Doorhy BIO 183L...

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Doorhy Colleen Doorhy BIO 183L Sec 219 2-28-07 Comparison of Photosynthetic Rates between Boiled and Unboiled Thylakoids at Varying Light Wavelengths Abstract To determine the photosynthetic rates of a blank and five different treatments including variations of thylakoids and colors of light a photosynthesis experiment was performed. The purpose of this experiment was to verify if boiled or unboiled thylakoids would yield photosynthetic rates and which color of light would also yield the highest photosynthetic rates. A blank test tube with 1.0 mL of phosphate buffer, 3.0 mL of dH 2 O, and 1.0 mL of 0.1% DPIP receives white light. Five different treatments were given in separate test tubes to determine the variations of photosynthetic rates at contrasting conditions. The amount of absorbance of each test tube was measure by a spectrophotometer in nanometers (nm). Absorption decreased in each treatment as the time increased at 30 second intervals of being exposed to varying colors of lights. The white light was found to be the color that yielded the highest photosynthetic rate, more so than blue and green light. Introduction This laboratory experiment focuses on photosynthetic light reactions and absorption of light energy. Photosynthesis is the process by which light energy is 1
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Doorhy converted to chemical bond energy (Beckmann 2005). This process is considered an anabolic reaction and can be summarized with this chemical equation: 6CO 2 + 12H 2 O + Light energy C 6 H 12 O 6 + 6CO 2 + 6H 2 O. The total process of photosynthesis contains two major series of reactions. These two reactions are known as light reactions and dark reactions. The light reactions require light energy and dark reactions can take place in light or dark environments, but do not require light energy to take place. These dark reactions do require chemical energy that is produced in the light reactions. Light reactions occur in the thylakoids and dark reactions occur in the stroma. Since leaves are the major sites of photosynthesis, all of the components within the mesophyll aids in the process. Thylakoids are a membranous system in the form of flattened, interconnected sacs found inside of chloroplasts (Campbell 2005). Chlorophyll resides in the thylakoid membranes. Embedded pigment molecules absorb the energy of sunlight or appropriate artificial light and each pigment is capable of absorbing specific wavelengths of light energy in the visible spectrum that humans can see. Chlorophyll a is the primary photosynthetic pigment because it is the most abundant pigment, and chlorophyll b and carotenoids are accessory pigments. Photons are discrete packets of light energy. In the light reactions of photosynthesis, light energy excites electrons in plant pigments such as chlorophyll, and boosts them to a higher energy level. These high-energy electrons reduce compounds (electron acceptors) in the thylakoid membrane, and the energy is eventually captured in the chemical bonds of NADPH and ATP. The rate of electron excitation can be measured when light hits chlorophyll. Dichlorophenol indole phenol
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