Problem: We are going to separate and identify pigments and other molecules from cell extracts through a process called chromatography. We will also test the theory that light and chloroplasts are required for light reactions to occur.
Background: Pigments are chemical compounds which reflect only certain wavelengths of visible light. This is what makes them seem colorful. Many things contain pigments including flowers, corals, and even skin. More important than their reflection of light is their ability to absorb certain wavelengths. Because pigments interact with light, they are very useful to autotrophs. These pigments help the user gain energy. Because pigments only absorb a narrow range of light, many different color pigments are needed to capture more of the sun’s energy. There are three basic classes of pigments which are chlorophylls, carotenoids, and phycobilins. There are several kinds of chlorophyll and they are greenish pigments. The most important one is chlorophyll A which is very important in making photosynthesis possible. Carotenoids are red, orange or yellow pigments and phycobilins are water soluble pigments found in the cytoplasm. (www.berkely.edu)
Chromatography comes from the Greek words chroma and graph for Color Writing. The technique was developed by Mikhail Tsvet who used it for separating pigments that made up plant dyes. Chromatography is a very valuable technique used for separating mixtures. It can be used for many things including find traces of drugs in urine and analyzing components of pollutants. (www.exploratorium.edu)
Chloroplasts are special organelles found in plant cells. These organelles contain the plant cells chlorophyll providing it its green color. Because chlorophyll is important in making photosynthesis possible, it is a very important organelle in keeping the plant alive. (www.cellsalive.com) Light reactions are the photo part of photosynthesis. These steps convert solar energy
References: “Photosynthetic pigments” 09 July 1997. http://www.ucmp.berkeley.edu/glossary/gloss3/pigments.html 12 November 2011 Owl Books. The Science Explorer. Henry Holt & Company, New York. “Black magic.” 1996. http://www.exploratorium.edu/science_explorer/black_magic.html. 12 November 2011. Quill Graphics. “Cell Organelles: The Chloroplasts.” 1994. http://www.cellsalive.com/cells/chloropl.htm. 12 November 2011.