1.3.5 Biochemical Tests: Proteins

The Biuret Test is a simple test used to detect the presence of peptide bonds in a sample, which indicates the presence of proteins. When peptide bonds are present, the solution turns purple.

infoNote

Method for the Biuret Test:

Prepare the Sample:

Place the food sample to be tested in a clean test tube. If the sample is solid, grind it and dissolve it in water to make it a liquid solution.

Add Sodium Hydroxide:

Add an equal volume of sodium hydroxide solution to the sample. This solution should be at room temperature.
Sodium hydroxide provides the alkaline conditions necessary for the test.

Add Copper(II) Sulfate Solution:

Carefully add a few drops of very dilute (0.05%) copper(II) sulfate solution to the mixture.
Mix the solution gently to ensure even distribution.

Observe the Colour Change:

If peptide bonds are present (indicating a protein), the solution will change to a purple colour.
If no protein is present, the solution will remain blue.

Interpreting the Results:

Positive Result: A purple colour change indicates the presence of proteins due to the reaction with peptide bonds.
Negative Result: If the solution stays blue, no protein is present in the sample. This test is useful for identifying proteins in various food samples, helping to confirm their presence based on their characteristic peptide bonds.

500K+ Students Use These Powerful Tools to Master Biochemical Tests: Proteins For their A-Level Exams.

Enhance your understanding with flashcards, quizzes, and exams—designed to help you grasp key concepts, reinforce learning, and master any topic with confidence!

80 flashcards

Flashcards on Biochemical Tests: Proteins

Revise key concepts with interactive flashcards.

Try Biology Flashcards

8 quizzes

Quizzes on Biochemical Tests: Proteins

Test your knowledge with fun and engaging quizzes.

Try Biology Quizzes

11 questions

Exam questions on Biochemical Tests: Proteins

Boost your confidence with real exam questions.

Try Biology Questions