PRAKTIKUM UJI PROTEIN

Summary

This video script details a laboratory experiment testing the presence of proteins in various samples such as milk, soy milk, egg whites, and agar-agar. The experiment utilizes the Biuret test to detect peptide bonds, NaOH and CuSO₄ to identify aromatic compounds in proteins, and lead acetate to test for sulfur. The results reveal that milk, soy milk, and egg whites contain peptide bonds and benzene rings, with egg whites being the only sample containing sulfur. The experiment offers a practical demonstration of protein testing techniques commonly used in biochemistry.

Takeaways

• 😀 The experiment aims to test proteins using different methods: Biuret test, Nitrogen test, and Lead acetate test.
• 😀 The Biuret test detects peptide bonds in proteins by adding CuSO4 and NaOH to samples.
• 😀 Samples like cow's milk, soy milk, and egg white turned purple, indicating the presence of peptide bonds.
• 😀 Agar-agar did not show a color change in the Biuret test, suggesting it lacks peptide bonds.
• 😀 The Nitrogen test uses NaOH to identify proteins with benzene rings by turning the sample orange.
• 😀 Cow's milk, soy milk, and egg white turned orange during the Nitrogen test, indicating proteins with a benzene ring structure.
• 😀 The Lead acetate test detects sulfur-containing proteins, causing black spots to appear on the filter paper.
• 😀 Only egg white showed black spots on the filter paper in the Lead acetate test, suggesting it contains sulfur.
• 😀 Cow's milk, soy milk, and agar-agar did not show black spots in the Lead acetate test, meaning they do not contain sulfur proteins.
• 😀 The results of all three tests help identify the protein content and specific characteristics of each sample.

Q & A

What is the primary goal of the experiment described in the transcript?

The main goal of the experiment is to test proteins in various substances, identify the presence of peptide bonds, and detect any abnormalities in the proteins, including the presence of sulfur.

What are the three key tests mentioned in the transcript?

The three tests mentioned are the Biuret test, the lead acetate test, and a heat test to detect sulfur in proteins.

What is the purpose of the Biuret test in this experiment?

The Biuret test is used to detect the presence of peptide bonds in proteins. The sample turns purple if peptide bonds are present.

What substances were tested in the experiment?

The substances tested in the experiment include cow's milk, soy milk, egg whites, and agar-agar.

How does the Biuret test react to different substances?

The Biuret test shows a positive result with cow's milk, soy milk, and egg whites by turning purple, indicating the presence of peptide bonds. Agar-agar, however, does not show this color change.

What is the significance of the color change to orange during the second test?

The orange color change indicates the presence of proteins that contain aromatic rings, such as benzene rings, in cow's milk, soy milk, and egg whites.

What was the result of the heat test with lead acetate?

When lead acetate was added to the samples and heated, only the egg whites showed a black spot on the filter paper, indicating the presence of sulfur in the protein.

What does the appearance of a black spot during the lead acetate test indicate?

The appearance of a black spot indicates the presence of sulfur in the protein, which was found in the egg whites during the test.

What is the role of NaOH in the experiments?

NaOH (sodium hydroxide) is added to the samples to adjust the pH and facilitate the reactions during both the Biuret test and the heat test with lead acetate.

Why does agar-agar not show any color changes during the tests?

Agar-agar does not contain proteins with peptide bonds or sulfur, which is why it does not show the characteristic color changes during the Biuret or lead acetate tests.