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Unformatted text preview: 1 LAB EXERCISE #10: PHOTOSYNTHESIS Pre-lab Assignment : Write two experimental protocols, one for the chromatogram experiment and one for the absorption spectrum experiment . Note about the Experimental Protocols: For the chromatogram experiment , focus hypotheses and predictions on the movement of each of the 5 pigments on the chromatography paper. You will write 5 predictions and 5 rationales, one for each pigment. For the absorption spectrum experiment , focus your hypotheses and predictions on the wavelengths of light, and their corresponding colors, that are absorbed by each of the pigments. You will make a prediction for each of the 5 pigments. Objectives: When you have completed this exercise, you should be able to: 1. Identify the pigments involved in photosynthesis by paper chromatography. 2. Give the function of chlorophyll and the accessory pigments. 3. Determine the wavelengths most useful for photosynthesis by determining the absorption spectrum of a pigment extract. Safety Procedures: This lab involves the use of organic solvents and acetone . Such materials are dangerous to the eyes and flammable. Students and Instructor must wear goggles during this lab. All organic waste, both liquid and solid, must not be poured into the sinks or thrown in the trash. All disposal of these materials is to be done using the proper receptacles in the hood . o Solid waste (i.e paper soaked with acetone) is to be placed in the hood in the beaker labeled Solid Waste. o Liquid waste is to be poured into the flask labeled Liquid Waste, also in the hood. Background: Evolutionary Implications of Photosynthesis One of the most important evolutionary developments that occurred on this planet was the ability of cells to convert light energy into carbohydrates . Current evidence shows that earth's early atmosphere contained no free oxygen. Because oxygen is a by-product of photosynthesis, the evolution of photosynthesis resulted in a change in earth's atmosphere from one probably composed of water vapor, carbon monoxide, carbon dioxide, nitrogen, methane, and ammonia to one based on oxygen. This change allowed cells, both autotrophic and heterotrophic , to utilize the processes of cellular respiration to extract energy from nutrients. Also, the production of free oxygen led to the formation of the ozone (O 3 ) layer in the atmosphere. This dramatically changed the earth's environment by reducing the amount of dangerous radiation reaching the earth's surface. This change allowed plants and animals to move from the water onto the land. All green plants produce oxygen as a by-product of photosynthesis . The rain forests are a major source of 2 oxygen for the earth and the ozone layer, and this is one reason why there is such an ongoing effort to save them. The greatest source of oxygen, however, comes from the green algae in the oceans, producing 70 80% of the oxygen that we breathe. Pollution and global warming are considered a producing 70 80% of the oxygen that we breathe....
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This note was uploaded on 04/07/2008 for the course BIOSCI 0050 taught by Professor Carollafarve during the Fall '07 term at Pittsburgh.
- Fall '07