Organic Molecule Investigation

Organic Molecule Investigation Lab Procedure Reference

Starch, Glucose, Lipid, and Proteins

Directions: Create a procedure to test for the presence of each organic molecule in your investigation. You may use the procedures below as a reference, but you need to tailor the procedure to your specific investigation.

For each type of molecule include:

1. Materials

2. Procedure (including safety and a control group)

3. Description of positive and negative result for each test.

Materials:

Goggles and aprons for everyone

Three test tubes

Wax pencil

Test tube rack

Unknown solution (placed at separate lab station)

Water control

Organic molecule control for station

test tube brush

soap

Test for Starch (Polysaccharide)

Materials: Iodine solution, starch control

• Iodine is an indicator that tests for the presence of starch. A blue-black or purple color indicates that starch is present.

1. Put on your safety equipment (goggles, apron) and keep them on for the rest of the lab time.

2. Using a separate dropper for each solution, add 10 drops of unknown solution to test tube 1, 10 drops of water control to test tube 2, and 10 drops of starch control to test tube 3.

3. Record the color of each test tube.

4. Add 3 drops of iodine solution to each test tube. Shake each test tube according to your teacher’s instructions.

5. Record the color of each test tube after the iodine is added.

6. Discard the contents of the test tubes and clean them carefully.

Test for Glucose (Monosaccharide)

Materials: hot plate, beaker with water, Benedict’s solution, test tube clamps, glucose control

• Benedict’s solution tests for the presence of simple sugars (monosaccharides and some disaccharides). A change from blue to yellow, orange, or red occurs if these simple sugars are present.

1. Heat the water bath to boiling on the hot plate.

2. Add 10 drops of unknown solution to test tube 1, 10 drops of water control to test tube 2, and 10 drops of glucose control to test tube 3.

3. Record the color of each test tube contents.

4. Add 10 drops of Benedict’s solution to each of these test tubes and place in a boiling water bath for 3 minutes.

5. After 3 minutes, remove the tubes and place them in the test tube rack to cool. Record the color of each test tube in your data table.

6. Discard the contents of the test tubes and clean them carefully (they may still be hot).

Brown Paper test for Lipids

Materials: brown paper, oil, water, lipid control

1. Label a piece of brown paper with unknown solution, water control, and lipid control.

2. Place a drop of each solution on the brown paper in the appropriate place.

3. Allow the paper to dry for a few minutes.

4. Hold the piece of paper up to the light. If a semi-transparent (translucent) spot is visible, the sample contains lipids. Record the appearance of the spots in your data table.

Test for Proteins

Materials: Biuret reagent, protein control

• When Biuret is mixed with a protein, it will produce lavender to violet purple color.

1. Add 10 drops of unknown solution to test tube 1, 10 drops of water control to test tube 2, and 10 drops of protein control to test tube 3.

2. Record the color of each test tube contents.

3. Add 10 drops of Biuret reagent to each test tube.

4. Record the color of the test tubes after adding the reagent.

5. Dispose of the contents of the test tubes and clean them carefully. Caution: Biuret is extremely caustic and will burn your skin. Avoid all skin contact with Biuret. Clean test tube thoroughly and carefully in a manner that you do not come into contact with the Biuret. Wash your hands at the end of this procedure. If there are any spills, please notify the teacher immediately.

6. Wash your hands thoroughly with soap and water.