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Test for Proteins

The Biuret test detects the presence of peptide bonds.Add an equal volume of sodium hydroxide to the sample.Add a few drops of very dilute (0.05%) copper(II) sulfate solution and mix gently.A purple colouration indicates the presence of peptide bonds.If no protein is present, the solution remains blue.

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Specification: AQA Biology (7401), AS-level, 3.1.4.1 General properties of proteins. Topic: Biological Molecules.

Key terms in this lesson

peptide bond
The covalent bond formed between the carboxyl group of one amino acid and the amine group of another, with the loss of water.

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