biomolecule tests

    Cards (5)

    • the test for starch is adding iodine, a positive result is from a browny orange colour to a blue-black colour
    • the test for the presence of lipids, is the emulsion test. Shake the substance with ethanol for a few seconds and then pour the solution into water. The more lipids present, the more milky.
    • the test for proteins is to first make the solution alkaline by adding sodium hydroxide, then add copper sulfate solution. A positive result should turn purple
    • all sugars can be classified as either reducing or non reducing. If you heat the sample with benedicts solution, and it stays blue, that means there is non reducing sugar present. If the solution forms either a green, orange or brick red precipitate, then reducing sugars are present
    • if the result for sugars stays blue, you can check for non reducing sugars by adding dilute hydrochloric acid (to a new sample), and heating it. Then neutralise with sodium hydrogen carbonate, then add benedicts
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