A Level Biology Practice Exam 2025 - Free A Level Biology Practice Questions and Study Guide

Question: 1 / 715

What is the purpose of the biuret test?

To identify carbohydrates in a solution

To test for the presence of lipids

To detect proteins by forming violet colored complexes with copper ions

The purpose of the biuret test is indeed to detect proteins in a solution by forming violet-colored complexes with copper ions. When protein is present, the peptide bonds in proteins interact with the copper ions (Cu²⁺) in the biuret reagent, leading to a color change that indicates the presence of proteins. This reaction is specific to peptide bonds and thus serves as a reliable method for identifying proteins in various samples.

Other options do not apply in this context: the biuret test does not identify carbohydrates, test for lipids, or measure the acidity of a solution. Each of those processes would require different specific tests or reagents tailored to detect those particular macromolecules or properties.

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To measure the acidity of a solution

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