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Research question/aim: How many and what kind of photosynthetic pigments are found in a green leaf? Hypothesis: Chlorophyll is required in plants for Photosynthesis to occur. It is a mixture of pigments, namely chlorophyll a, chlorophyll b, and certain carotenoids. In intact plants these pigments are present in the chloroplasts, held in the structures called grana. Several distinct photosynthetic pigments in the chlorophyll are needed for the absorption of light of different wave-lengths, each pigment being responsible for the absorption of a different wavelength. Chlorophyll is mostly insoluble in water; however it can be extracted with organic solvents. To be able to see different chlorophyll pigments, they have to be separated by a process called chromatography. Hence I expect several pigments, of different colors to be present in the leaf, taking part in the process of photosynthesis. The colors I expect to see are for instance yellow, green and blue/green. The pigments I expect to see by the chromatography are Carotene (Rf 0.95), Phaeophytin (Rf 0.83), Xantophyll (Rf 0.71), Chlorophyll a (Rf 0.65), and Chlorophyll b (Rf 0.45). Rf is the distance moved by the pigment divided by the distance moved by the solvent front. This factor enables you to identify the pigment seen. Name of the pigment Color of the pigment Rf value Carotene Yellow 0.95 Chlorophyll a) Blue/green 0.83 Chlorophyll b) Green 0.71 Phaeophytin Yellow/grey 0.65 Xantophyll Yellow/brown 0.45 Materials: Ø Boiling tube Ø Fresh green leafs, with soft rather than waxy surface Ø Small bowl Ø Acetone Ø Capillary tube Ø Chromatography paper Ø Stapler Ø Toothpick Ø Small knife Ø Chromatography solvent Method: First of all fresh green leaves have to be picked from outside.
Approximate Word count = 1091
Approximate Pages = 4.4
(250 words per page double spaced)
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