Photosynthesis Lab Color of Light Emma Williams Section 423 Jennifer Levine 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 Introduction All plants use the process of photosynthesis to produce energy needed for daily function from sunlight Green plants require water carbon dioxide chloroplasts and light to produce carbohydrates and oxygen The equation for this reaction is H2O CO2 light CH2O N O2 The light dependent reaction in the photosynthesis is made possible by the transfer of highenergy electrons These electrons are being passed on by electron acceptor molecules and are being reduced and oxidized Also during the light dependent reaction NADP is reduced to NADPH which moves forward the synthesis reactions To track this process one can use a dye DPIP which intercepts these electrons to show the flow of electrons The DPIP will change color from blue to colorless if photosynthesis occurs The equation DPIP blue e DPIP colorless demonstrates this process The equation 2DPIP 2H2O Chloroplasts 2DPIPH2 O2 illustrates how this process occurs The color of light the plant is exposed to affects the rate of photosynthesis Different colors of light give off different types of waves which can then even be reflected When the chloroplasts are exposed to a red light the rate of photosynthesis will increase and the more light will transmit through the chloroplasts Methods and Materials Number the four test tubes 1 4 but be sure not to touch the sides of the tubes to avoid fingerprints Instead handle the test tubes by the top Then use Kimwipes to wipe each tube clean removing any fingerprints that could affect the ability of light to pass through Cover the third test tube in aluminum foil including a cap for it This will be the dark tube in which no light enters Be sure to remove the foil before putting it in the spectrophotometer which is set at 605 nanometers This is the wavelength that balances out the blue of the DPIP dye Keep this test tube covered at all times This is the control Keep the large Erlenmeyer flask with distilled water between the test tube rack and the gooseneck lamps Test tube 1 will be the tested under red light Test tube 2 will be tested under blue light Test tube 3 will be tested under green light Test tube 4 will be tested under black light Obtain suspended photosynthesizing chloroplasts boiled and unboiled from your instructor and keep them on ice from an ice cooler Add 1mL of phosphate buffer 1mL of DPIP dye and water to each test tube using a 1mL transfer pipette Add 3 drops of unboiled or boiled chloroplasts to the appropriate tubes Immediately cover the test tubes with Parafilm Turn them upside down and right side up to mix the contents Then wipe with Kimwipes again Place calibration tube into sample holder close lid and adjust spectrophotometer to 100 transmittance Remove test tube close lid and quickly proceed to next three test tubes Each tube should be inverted and read one after another Remember to mix the tubes invert them then wipe off outside before each reading Record reading in a chart and mark the first readings as time zero Mix and read each tube at 5 10 and 15 minutes with the calibration tube read before each 5 minute interval Between each reading place the tubes on its appropriate test tube rack
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