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Protein and Lipids Tests in a Snap! Unlock the full A-level Biology course at http://bit.ly/2tjNUH6 created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University. SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks. Sign up today and together, let’s make A-level Biology a walk in the park! The key points covered in this video include: 1. Proteins - Biuret Test 2. Lipids - Emulsion Test Proteins - Biuret Test The Biuret test can be used to test for proteins by detecting the presence of peptide bonds. The sample to be tested is placed in a clean test tube. Biuret A (sodium hydroxide) is then added to the test tube. A few drops of Biuret B (copper (II) sulphate) is then added and the solution is gently mixed. If protein is present, the colour of the reagent changes from blue to purple. Lipids - Emulsion Test The emulsion test can be used to detect the presence of lipids. The sample to be tested is placed in a clean test tube. Ethanol is then added to the test tube and the solution is mixed thoroughly to dissolve any lipid. Water is then added to the test tube and mixed gently. A cloudy white substance indicates that lipids are present in the sample. This cloudy white substance appears as lipids are not soluble in water so they come out of solution and form an emulsion. Summary The Biuret test is used to test for proteins by detecting the presence of peptide bonds Biuret's reagent turns from blue to purple if protein is present The emulsion test is used to test for the presence of lipids Lipid solutions form emulsions when water is added as they are unable to dissolve in water
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