Name_____________________
Identifying Organic Compounds
Introduction
In this investigation, you will use several indicators to test for the presence of lipids, carbohydrates, and
proteins in various foods. An indicator is a substance that changes color in the presence of a particular
compound.
Safety
Wear goggles and an apron. If you spill anything on your hands, wash them. Be careful to not break glassware.
Procedure
Part 1: Testing for Lipids
1. Place a small drop of your food sample on a paper towel and let it dry 10-15 minutes. Hold the piece of
brown paper towel up to a bright light. The presence of a translucent spot indicates the presence of lipids.
2. Do this for all TEN foods that you are testing. It’s easy if you make 10 spots on the towel and test together.
Part 2: Testing for Carbohydrates (sugar)
The indicator for this is benedict’s solution. If sugars are present, it will turn yellow/orange/red in color.
1. Get 5 Test Tubes. You will test the first 5 foods on your chart first.
2. Fill up the pipette with the food from the beaker at the front of the room and put 3 drops of the food
labeled on your test tube.
3. Add 3 drops of BENEDICT’S SOLUTION to each tube and shake LIGHTLY to mix components together.
4.
5.
6.
7.
Put all test tubes in the hot beaker of water for 5 MINUTES.
Record your results on your table.
Remove with test tube holders and rinse out the tubes very well. Be careful with heated test tubes.
Repeat with the next 5 on your chart.
Part 3: Testing for Carbohydrates (starch)
The indicator for this is iodine. In the presence of carbohydrates, it will turn black/blue in color.
1. Fill the pipette with each solution and put 3 drops of each in the appropriate well (they are numbered!!
See the table below!!)
2. Add 3 drops of iodine to each well.
3. Record your results in the data table.
4. Rinse out the tray very well.
Part 4: Testing for Proteins
The indicator for this is Biuret Reagent. If proteins are present, it will turn violet/purple in color.
1. Put the appropriate substance in each well again.
2. Add 3 drops of BIURET REAGENT to each well.
3. Record your results on your table.
4. Rinse out the tray very well.
**CLEAN UP ALL MATERIALS and RAISE YOUR HAND so I can come check your area!!
Identifying Macromolecules Lab
Pre-Lab Discussion
1. What is an indicator? __________________________________________________________________
2. What is the purpose of using just water in one of your test tubes? ______________________________
___________________________________________________________________________________
3. What is the purpose of washing the trays thoroughly after each test? ___________________________
____________________________________________________________________________________
Results
Lipid Test
Substance
Are lipids
present?
Carbohydrate Test
Benedict’s
Color
Are sugars
present?
Iodine’s
Color
Protein Test
Are
starches
present?
Biuret
Color
Are
there
proteins
present?
1. Honey
2. Egg white
3. Corn oil
4. Letuce
5. Milk
6. Peanut Butter
7. Potato
8. Apple Juice
9. Water
10. Unknown
Conclusion
1. Which substances contain lipids? ________________________________________________________
2. Which substances contain starch? ________________________________________________________
3. Which substances contain simple sugar? __________________________________________________
4. Which substances contain protein? _______________________________________________________
5. Which substance did not test positive for anything? _________________________________________
6. People with diabetes are instructed to avoid foods that are rich in carbohydrates. How could your
observations in this investigation help you decide whether a food should be served to a person with
diabetes? ___________________________________________________________________________