Experiment: Tests for Biomolecules Carbohydrates, proteins, lipids, and nucleic acids are the biological molecules that make up an

organism. In this experiment, tests for three of the four biomolecules are utilized to identify the presence or absence in various food samples.

Materials and Apparatus: Test tubes

Test tube racks Droppers Mortar and pestle

Molisch’s reagent Glucose

Sucrose

Agar

Concentrated H2SO4 Olive oil Concentrated HNO3

KMnO4 NaOH

CuSO4

Gelatin

To bring: Mung bean seeds (50g) Milk (25mL)

Cooking oil (25mL)

Procedure:

I. Test for Carbohydrates 1. Molisch Test: In three separate test tubes, place 5 drops each of Molisch’s reagent and 5 drops

of glucose, sucrose, or agar. Mix gently by shaking the test tube. Record any changes. Tilt the test tube, and carefully add 10 drops of concentrated H2SO4. Do not mix. Record any changes.

Disposal: Dispose in the nonhalogenated waste container.

II. Tests for Lipids 1. Calvert’s Test: In a test tube, place 5 drops of concentrated H2SO4 and 5 drops of olive oil

sample. Record any changes, and add 5 drops of concentrated HNO3. Record any changes. Perform the test inside the fume hood due to toxicity.

Disposal: Dispose in the nonhalogenated waste container.

2. Crouzel-Dupin’s Test: In a test tube, place 5 drops of olive oil and 5 drops of KMnO4 solution.

Record any changes. Disposal: Dispose in the nonhalogenated waste container.

III. Test for Proteins 1. Biuret Test: In a test tube, add 5 drops of gelatin solution. Add 5 drops of NaOH solution and 5

drops of CuSO4 solution. Mix the solution, and let the solution stand for a few minutes. Record any changes.

Disposal: Dispose in the sink.

IV. Testing of Food Samples

1. Preparation of mung bean seeds: Grind about 15g of mung beans in 15mL tap water using a mortar and pestle. Let stand for 30 minutes, and transfer to a test tube.

2. Test the mung bean seed extract, milk, and cooking oil if they contain carbohydrates, lipids,

and/or proteins. Disposal: Dispose according to above.

Experiment Data Sheet Name:

Date: I. Test for Carbohydrates

Color of original solution Molisch’s reagent H2SO4

Color of original solution -------------------------------

Sucrose

Glucose

Agar

II. Tests for Lipids

Color of original solution H2SO4 HNO3 KMnO4

Color of original solution -------------------------------

Olive oil

III. Test for Proteins

Color of original solution NaOH/CuSO4

Color of original solution -------------------------------

Gelatin

IV. Testing of Food Samples

Does it contain… Carbohydrates? Lipids? Proteins?

Mung bean seeds

Milk

Cooking oil

Question: For part IV, explain how you were able to determine the content of each food sample.