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Identification of Biological Important Compounds

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Valentina Zunarelli IB Biology Practical Identification of Biological Important Compounds Introduction Starch is a common name applied to a white, powdery, odorless, tasteless, complex carbohydrate, (C6H10O5)x, it is found in the seeds of cereal plants and in bulbs and tubers in great amounts. Starch is manufactured by green plants during the process of photosynthesis. It forms part of the cell walls in plants, constitutes part of rigid plant fibers, and serves as a kind of energy storage for plants. Sugar, chemical compounds in the carbohydrate group that are readily soluble in water; are colorless, odorless, and usually crystallizable; and are more or less sweet in taste. ...read more.


Lipids are hydrophobic. This group of molecules includes fats and oils, waxes, phospholipids, and some other related compounds. Fats and oils are made from two kinds of molecules: glycerol (a type of alcohol) and three fatty acids joined by dehydration synthesis. Aim To test whether five unknown substances contain starch, sugars, proteins or lipids, and then identify what the substances could be. Apparatus -oil -alcohol (absolute ethanol) -copper sulphate -potassium hydroxide -iodine solution -benedict's reagent -bunsen burner -tongs -palette -tongs -matches -pipettes -test tubes -unknown powder 1: fine yellowish powder -unknown powder 2: fine white powder -unknown powder 3: fine white power (like flour) ...read more.


Lipids: Shake some olive oil in a test tube with the unknown powder for one minute; add an equal amount of water. A cloudy white precipitate indicates lipids. Each test should be carried out for each unknown powder and the results should be recorded. Results These were the results collected from each of the tests carried out. Table Showing Appearance and Presence for the Starch Test Powder 1 2 3 4 5 Appearance light yellow dark brown black Yellowish v. light yellow Starch no yes yes No no Table Showing Appearance and Presence for the Sugar Test Powder 1 2 3 4 5 Appearance (before boiling) milky cloudy white Transparent insoluble white powder (after boiling) orange-yellow cloudy bright green Brick-red brownish green Sugars yes (a lot) no yes (little) Yes (a lot) yes (v. ...read more.

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