LS2lab3 - Mrigender Virk ID 003268270 Life Science 2...

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Mrigender Virk ID 003268270 5-04-2005 Life Science 2 Section Lab 3: The Pigments of Photosynthesis Introduction Photosynthesis is the metabolic process that creates usable energy from a solar form. The solar energy is turned into glucose, a six carbon carbohydrate, by the photosynthesis equation which is 6CO2 + 12H2O -> C6H12O6 + 6H2O + 6O2 and then glucose can finally be converted to ATP energy and NADPH which binds to high energy electrons. There are two parts to photosynthesis: the light dependent reactions and the light independent reactions. In the first part, light dependent reactions, photons are absorbed to create the ATP and high energy electrons while in the light independent reactions the energy stored is used to fix carbon dioxide and produce glucose. This second part is also known as the Calvin Benson Cycle. The molecules that absorb light energy are known as pigments and are divided into three classes which are chlorophylls, carotenoids, and phycobilins. Chlorophylls are the only pigments that can convert the light energy into chemical energy so the other pigments are known as accessory pigments in that they can absorb different wavelengths of light but they must pass on the energy to chlorophylls a and b. Carotenes are divided into carotenes and xanthophylls and they absorb violet and blue light which makes them look yellow, orange, or red. Phycobilins are the last group of pigments with two common ones being phycocyanin and phycoerythrin which contribute the colors to red algae and cyanobacteria. The main objective of this lab is to see whether or not environmental conditions affect the pigment compositions of photosynthetic organisms. All pigments have an absorption spectrum which is in between 400-700 nanometers which tells what range it can absorb by using a spectrophotometer. Some pigments only absorb one type of light and others will peak in absorbance on two parts of the spectra. Thin Layer Chromatography, also known as TLC, is used to separate organic compounds. We use this along with Spectrophotometry to see how barley is affected by its environment. TLC is done by dissolving a sample in a solvent and spotting it onto a TLC strip and then placing it in a shallow holder with another solvent. By capillary action the solvent moves up the strip and then after evaporation the components are left at
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This note was uploaded on 05/02/2008 for the course LIFESCI ls 2 eng 3 taught by Professor All during the Spring '04 term at UCLA.

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LS2lab3 - Mrigender Virk ID 003268270 Life Science 2...

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