Overview
This lab focuses on testing for the presence of macromolecules—carbohydrates, proteins, and lipids—using various indicator tests. Nucleic acids are not included in today’s experiments.
Types of Macromolecules
- The four main macromolecules are carbohydrates, proteins, lipids, and nucleic acids.
- Carbohydrates, proteins, and lipids are essential for life and found in all living things.
Lab Preparation & Safety
- Always wear safety glasses and tie back long hair.
- Begin with clean, empty test tubes for each test.
Carbohydrate (Simple Sugar) Test
- Add a small amount of sugar solution to a test tube.
- Mix in Benedict’s solution and apply heat for about 30 seconds.
- Presence of simple sugars is indicated by an orange color change.
Protein Test
- Add a small amount of gelatin solution to a test tube.
- Add Biuret reagent (referred to as "PC solution" and "verret regain" in transcript).
- A purple color indicates the presence of proteins.
Lipid Tests
- Rub vegetable oil on green paper; a translucent stain shows lipids are present.
- Water on paper does not create a translucent stain, unlike lipids.
- Mix vegetable oil and water in a test tube; they do not mix.
- Mix vegetable oil and ethanol in a test tube; they mix and form glass-like beads.
Starch Test
- Add starch solution to a test tube.
- Add iodine solution; a black color shows starch is present.
Testing Known and Unknown Substances
- Test substances like peanut butter, milk, apple juice, egg whites, potato, corn chips, and bread using all indicators.
- Also, test an unknown sample to determine which macromolecule is most present.
Cleanup and Reporting
- Always clean test tubes between tests.
- Fill out the laboratory report with all required data.
- Clean up all supplies and return them to their proper place.
Key Terms & Definitions
- Macromolecule — Large molecule essential for life, including carbohydrates, proteins, lipids, and nucleic acids.
- Benedict’s Solution — Indicator for simple sugars; orange color means positive result.
- Biuret Reagent — Indicator for proteins; purple color means positive result.
- Iodine Solution — Indicator for starch; black color means positive result.
- Lipid — Fat molecule that forms translucent stains and does not mix with water.
Action Items / Next Steps
- Complete laboratory report, ensuring all results are recorded.
- Test all known and unknown samples with each macromolecule indicator.
- Clean and store all lab equipment after finishing.