Biuret's Test

Summary

In this video, we perform the Biuret test to detect proteins, which are polymers of amino acids linked by peptide bonds. The test utilizes Biuret's solution, which turns violet in the presence of peptide bonds, indicating a positive result. We will test eight solutions, including water, egg albumin, amino acids, Gatorade, apple juice, coconut water, corn juice, and soy milk. After adding Biuret's solution to each, we observe that only egg albumin and soy milk test positive for protein, demonstrating the effectiveness of the Biuret test in identifying protein presence.

Takeaways

• 🧪 Today, we performed the Biuret's test for proteins.
• 🔗 Proteins are polymers made of amino acids connected by peptide bonds.
• 💜 Biuret's solution reacts with peptide bonds, producing a violet color.
• 🔍 Single peptide bonds occur between each amino acid pairing.
• 📏 Proteins, often called polypeptides, can consist of tens to hundreds of amino acids.
• 📝 A variety of solutions were prepared for testing: water, egg albumin, amino acids, Gatorade, apple juice, coconut water, corn juice, and soy milk.
• 📊 Each solution was added to labeled test tubes for the experiment.
• 💧 A full dropper of each test solution was combined with a half dropper of Biuret's solution in each tube.
• 🔵 A blue solution indicates the absence of protein (negative result).
• 💜 A violet solution indicates the presence of protein (positive result), with egg albumin and soy milk testing positive.

Q & A

What is the purpose of the Biuret's test?

The Biuret's test is performed to detect the presence of proteins in various solutions.

What are proteins made of?

Proteins are polymers of amino acids joined together by covalent peptide bonds.

What color does Biuret's solution turn in the presence of proteins?

Biuret's solution gives a violet color when it reacts with peptide bonds, indicating the presence of proteins.

What are the types of solutions tested in this experiment?

The solutions tested include water, egg albumin, amino acids, Gatorade, apple juice, coconut water, corn juice, and soy milk.

How should the test tubes be labeled for the experiment?

The test tubes should be labeled one through eight to correspond with the solutions being tested.

What does a blue solution indicate in the Biuret's test?

A blue solution indicates the absence of protein, resulting in a negative test result.

What is the significance of single peptide bonds in proteins?

Single peptide bonds occur between each amino acid pairing, forming the primary structure of proteins.

What does the term 'polypeptides' refer to?

Polypeptides refer to proteins that are often made up of tens or even hundreds of amino acids joined together.

What was observed as a positive result in this experiment?

The test today shows that egg albumin and soy milk test positive for protein, indicated by a violet color.

How do you conduct the Biuret's test?

To conduct the test, add a full dropper of each solution to the appropriate test tube, then add a half dropper of Biuret's solution and shake well.