This document describes several common tests used to identify biological molecules, including Benedict's test for sugars, iodine solution for starch, the emulsion test for lipids, Sudan III staining for lipids, the Biuret test and Millon's test for proteins. Each test is briefly explained, noting the materials used and expected results to indicate the presence of the targeted molecule.

1. Identification of Biological
Molecules
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2. Testing for the presence of sugars
(Benedict’s test)
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3. Testing for the presence of sugars
(Benedict’s test)
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4. Testing for the presence of sugars
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5. Testing for the presence of starch
(iodine solution)
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6. Testing for the presence of lipids
(emulsion test)
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7. Sudan III
• Tissue that has been ground up is
transferred to a test tube containing water
and boiled
• Oil droplets will escape the tissue and rise
to the surface
• Add 2 cm3 Sudan III, shake and allow the
oil to settle
• Oil will be stained red
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8. Testing for presence of protein
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9. Biuret test
• Suitable for soluble proteins
• Add equal amount of 1% potassium hydroxide
(KOH) to solution
• Add a few drops of 1% copper (II) sulphate
(CuSO4) solution down the side of test tube
• A blue ring at the surface of the solution
indicates protein
• On shaking, the blue ring disappears and the
solution turns purple
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10. Millon’s test
• For insoluble proteins
• 6 drops of Millon’s reagent to a small
amount (3 cm3) of solution or suspension
of protein and boil for 5 minutes
• After cooling, add a few drops of 1%
sodium nitrite
• If protein is present, a brick-red
precipitate appears on the surface
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