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Organic Macromolecules Lab Report

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The objective of this experiment is to identify macromolecules by examining the chemical changes and analyzing the results based on the properties of known solutions and macromolecules. This lab, identifying organic macromolecules, focuses primarily on the colour changes of the solutions and the molecular changes that lead to these physical changes.
Iodine Test
Two common polysaccharides, starch and glycogen, serve as energy storage molecules in plants and animals respectively. Starch consists of two major polysaccharides: amylose and amylopectin, both of which are composed of chains of D-glucose units joined by α-1, 4-glycosidic bonds. While amylose has an unbranched helical structure, amylopectin is highly branched with α-1, 6-glycosidic bonds joining the branches at the branch points. Amylopectin can be found in both starch and glycogen (Brown & Poon, 2014). The technique that will …show more content…

In the iodine test, Lugol’s solution containing iodine and potassium iodide will serve as the indicator. This test is chosen for determining the presence of starch or glycogen because the amylose in starch reacts with iodine and forms a dark blue complex – the amylose-iodine complex. The complex is formed by iodine atoms fitting into the linear helical chain of amylose, increasing the chain length. The wavelength of maximum absorption is in turn increased because the reaction changes the energy level spacing, giving the complex a blue black colour (Rundle & Foster & Baldwin, 1944). Similarly, the reaction between glycogen and iodine also produces a red-brownish colour which is less intense than amylose’s blue black. This

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