Macromolecules - Student Protocol

HYPOTHESES: In this activity, the experimental hypothesis might be that the addition of an indicator dye to each test solution will result in a color change if the test solution contains the macromolecule of interest. The null hypothesis might be that the addition of an indicator dye will not result in a color change in any of the test solutions.

Place 16 clean test tubes in a tube rack in four rows of four tubes and label each row A through D and each column 1 - 4.

Label each test tube with its corresponding position in the test tube rack.

After this, stir solution A thoroughly and use a pipette to add 4 mL of solution A to each tube in Row A.

Next, stir solution B until it is well mixed and use a new pipette to add 4 mL of solution B to each tube in Row B.

After stirring solution C thoroughly, add 4 mL of solution C to each tube in Row C.

Then add 4 mL of soybean-derived vegetable oil to each tube in Row D.

When all of the tubes have been filled with their respective test solutions, add 200 mL of water to a 400 mL beaker on a hotplate and set the hotplate to high.

To perform the Benedict's Test, add 2 mL of Benedict's reagent to test tubes A1, B1, C1, and D1 while the water is warming.

Observe the initial color of the tubes.

When the water begins to boil, transfer each test tube to the beaker and heat the tubes in the boiling water bath for 3 - 5 minutes.

Then, record the final color of each of the tubes in the appropriate cells of the table and turn off the hotplate. Click Here to download Table 1

To perform an Iodine-Potassium-Iodide Test, first observe the color of the solutions in the test tubes in column 2.

Then, add 1 mL of iodine potassium iodide reagent to tubes A2 to D2 and record the final color change in each of the tubes.

For the Sudan IV Test, observe and record the color of the solutions in the test tubes in column 3.

Then, add 2 - 3 drops of Sudan IV reagent to test tubes A3 through D3 and record the color change, if any, in each tube.

For the Biuret Test, observe the color of the solutions in the test tubes in column 4.

Then, add 1 mL of Biuret reagent to test tubes A4 through D4 and record the final color in each of the tubes.

Using the results from the indicator tests, each of the four original solutions can be identified as a sugar, starch, lipid, or protein. Refer to the Concepts video to help you determine which tubes contain which macromolecules.

First, look at the results from the Benedict's Test. Determine which of the test solutions contain sugar based on your results.

Next, create a bar graph with your five plant species listed on the x-axis and the surface area in cm indicated on the y-axis.

Next, look at the results from the Iodine-Potassium-Iodide Test. Determine which of the test solutions contain starch.

Now, review the results from the Sudan IV Test. Using these observations, determine if any of the test solutions contain lipids.

Finally, look at the results from the Biuret Test. Determine if any of the test solutions contain proteins.