Name:
CHEMICALS OF LIFE LAB
Date:
The fundamental chemical components of cells can be grouped into
four basic categories: carbohydrates, lipids, proteins and nucleic acids. You
will be testing various substances for the presence of these macromolecules.
Procedure:
1. Obtain 6 microcentrifuge tubes. Label each A, B, C, D, E or P (Plant)..
Carbonhydrate Test – use iodine indicator
1. Add 12 drops of solution A to tube A, 12 drops of solution B to tube
B, etc . . .through E and 12 drops of plant solution to tube P.
2. Add 2-4 drops of iodine to each tube.
3. If carbohydrates are present the color will change from yellow/brown
to dark purple/almost black.
4. Call the teacher over.
5. Rinse out the remaining 5 tubes with water.
Protein Test – use biuret indicator
1. Use the remaining 5 tubes from the carbohydrate test.
2. Add 12 drops of solution A to tube A, 12 drops of solution B to tube B,
etc. . . through E and 12 drops of plant solution to tube P.
3. Add 5-10 drops of biuret to each tube.
4. If protein is present the color will change from light blue to light
purple.
5. Call the teacher over.
6. Rinse out the remaining 4 tubes with water.
Lipid Test – use Sudan III indicator
1. Use the remaining 4 tubes from the protein test.
2. Add 12 drops of solution A to tube A, 12 drops of solution B to tube B,
etc. . . through E and 12 drops of plant solution to tube P.
3. Add 5 drops of Sudan III to each tube and mix vigorously.
4. If lipids are present two distinct layers will form, with the top layer
being pink/orange/brown or pink/orange/brown oil droplets will form
when shaken vigorously.
5. Call over the teacher.
6. Rinse out the remaining 3 tubes with water.
Nucleic Acid Test – use diphenylamine (dpa) indicator
1. Use the remaining 3 tubes from the lipid test.
2. Add 6 drops of solution A to tube A, 6 drops of solution B to tube B,
etc . . . through E and 6 drops of plant solution to tube P.
3. Add 12 drops of diphenylamine (dpa) to each tube.
4. Place all 3 tubes in a hot water bath at 250C for 20 minutes.
5. If DNA is present the color will change from colorless to purple/blue.
Data Table: ** For solutions A-E, you should only have one positive (+) test
for each macromolecule. Solution P could test positive for any test.
Substance
Name
Solution Carbohydrate
Protein
Lipid
Nucleic
Acid
A
B
C
D
E
P
(plant)
1. Which solution acted as your negative control? ____________________
2. Which solution acted as your positive control for each test?
carbohydrates: _____________
proteins: __________________
lipids: ____________________
nucleic acids: _______________
3. What macromolecules (big molecules) were present in your plant tissue?