BIOL130L Study Guide - Final Guide: Iodine, Starch, Glycogen
4 Dec 2015
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Positive set up to ensure that you are getting an effect where you should get an effect ie. starch in beaker #8 should come out positive for iodine test. Negative set up to ensure you do not get an effect where you shouldn"t get an effect ie. distilled water, should be negative throughout. Iodine test tests for presence of starch (blue-black) and glycogen (reddish-brown) Starch storage polysaccharide found in plants amylose (alpha 1-4) and amylopectin (alpha 1-6) Glycogen storage polysaccharide found in animals highly branched. Starch and glycogen differ by their overall shape and degree of branching. Amylose in starch reacts with iodine to give blue colour and multi branched components for reddish-brown. Benedict"s test tests for reducing sugars, if blue solution develops coloured precipitate like yellow, green, red, brown or a combination. Due to free aldehyde group that reduces the cupric ions (cu++) in the benedict"s solution to cuprous ions (cu+). Combine with oxygen to produce precipitate of cu2o.
