Lab 1: Biomolecules Test

Materials:
Test tubes
Test tube rack
Test tube clamp
Sharpie
Water bath
Lugol’s iodine
Biuret reagent – (CuSO4
and NaOH)
Benedict’s solution
Brown paper
Stirring rod
Food samples
Droppers

Test Protocols:
I. Lipids - Brown Paper Bag Test
1. Label a section of brown paper with the sample being tested.
2. Using a glass stirring rod, rub the food to be tested until a “wet” spot appears on
the paper. With a paper towel, rub off any excess food that may stick to the
paper.
3. Set the paper aside to dry, about 10 to 15 minutes.
Positive Test: Hold the paper to the light. A translucent spot indicates the
presence of lipids.


II. Proteins - Biuret Test
1. Place 2 full droppers of the specimen to be tested into a test tube.
2. Add 5 drops of NaOH and 5 drops of CuSO4 to the tube.
3. Gently shake the test tube.
Positive Test: Biuret is clear or light blue in the absence of protein, and pink or
blue-violet in the presence of protein.


III. Carbohydrates - Lugol’s Iodine Test for Starch
1. Place 2 full droppers of the specimen to be tested in to a test tube.
2. Add 5 drops of Lugol’s Iodine solution.
Positive Test: Lugol’s Iodine changes from yellow to blue or black in the
presence of starch.

Benedict’s Test for Monosaccharide
1. Place 2 full droppers of the specimen to be tested into a test tube.
2. Add 1 full dropper of Benedict’s solution to each tube.
3. Gently shake the test tube.
4. Incubate the tubes in the hot water bath for 3-5 minutes.
Positive Test: Benedict’s changes from blue to green, yellow, or orange when
heated if a monosaccharide is present.