WLHS/Biology
Name Per
LAB: Macromolecule Testing
INTRODUCTION:
One characteristic of life is that living things are made up of molecules containing carbon. These are called ORGANIC
MOLECULES. In our class we have been referring to them as macromolecules since they are necessary for life. The
most common organic compounds found in living organisms are LIPIDS, CARBOHYDRATES, PROTEINS, and
NUCLEIC ACIDS. Common foods, which often consist of plant materials or substances derived from animals, are also
combinations of these organic compounds. Simple chemical tests with substances called indicators can be conducted to
determine the presence of organic compounds. A color change of an indicator is usually a positive test for the
presence of an organic compound.
PURPOSE:
To use indicators to test for the presence of lipids, carbohydrates, and proteins in various foods.
HYPOTHESIS: Which foods will contain which macromolecules? Check the box below each macromolecule you think
each food contains.
Food Lipids Carbohydrates Proteins
Water
Oil
Milk
Oatmeal
Apple Juice
MATERIALS:
Indicators (Biuret reagent, Benedict’s solution, Lugol’s solution)
Food in bottles, 10 test tubes, beaker, hot plate, test tube holder, brown paper towel, 2 well plates.
PROCEDURE:
LIPIDS (1 test)
TEST 1: Testing for Lipids: Part I
1. Tear off a piece of paper towel 30 cm long and put the names of your group members in the upper right hand
corner.
2. Draw 6 small squares, approximately 3 cm each, and label each with the name of 1 of the foods (water, oil, milk,
oatmeal, apple juice, and Unknown X).
3. Put 1 drop of each of the foods in the corresponding boxes on the paper towel.
4. Put the paper towel aside while you do the other 4 tests.
5. When the paper towel is dry, record your observations in the data table below. Look for a grease stain.
CARBOHYDRATES (2 tests)
TEST 2: Testing for Starches
1. Fill 6 wells in your well plate: water, oil, milk, oatmeal, apple juice, and Unknown X. (see diagram on page 3)
2. Add 10 drops of Iodine Solution to each well.
3. Check for any color change and record data in table.
4. Clean and dry well plate
TEST 3: Testing for Sugars
1. Put 1 dropper full of each food (water, oil, milk, oatmeal, apple juice, and Unknown X) in 6 different test tubes.
Make sure to LABEL all test tubes.
2. Add 10 drops of Benedict’s Solution to each test tube and place them all CAREFULLY into the hot water bath
for 3-5 minutes.
3. Remove test tubes from hot water bath using designated tongs and place them into test tube holders. Note the
color change and record into the table.
4. Wash all test tubes and place in test tube racks upside-down to dry.
