Biological Macromolecules An Inquiry Investigation Into the Properties of Certain Foods…..

Purpose: To determine which biological macromolecules are found within each of the following foods: Peanuts Crackers Eggs Milk

Your Goal: To design a set of experiments that will illustrate which biological macromolecules are present in each of the foods previously listed. You must include the following sections in your lab write up: Title Purpose Apparatus Procedure (for each of the 4 tests) Data Results & Error Analysis Conclusion

Questions to think about: Which macromolecules do you think are present in each of the foods listed? What kinds of data will you collect? What are your variables? What is your control? Can each food have more than one type of macromolecule? How will you know? How will you convey your results to the reader?

Testing for Simple Sugars: Benedict’s Test: In the presence of monosaccharides, a positive test results in a yellow-orange colored solution. MUST be heated to activate the test! ONLY tests for simple sugars; no positive tests for polysaccharides.

Testing for Starch (Polysaccharides): Starch Test: In the presence of starch, a positive test results in the Iodine solution turning a deep blue-black color. Does NOT need to be heated.

Testing for Lipids: Sudan IV Test: In the presence of lipids, this compound will stain the long hydrocarbon chains of fatty acids a red-orange color. Must dissolve the lipids in ethanol (alcohol) first (non-water soluble). No heat necessary.

Testing for Proteins: Biuret Test: In the presence of a protein, this solution will produce a violet colored solution. Must mix well (shake vigorously) Allow solutions to sit for at least 5 minutes BEFORE establishing if there has been a reaction or not.

What Materials Can You Use? The following is a list of materials available to you: Test tubes The 4 test solutions previously discussed Ethanol Alcohol burners Saliva (hint, hint…..!) Beakers, graduated cylinders, and/or flasks Anything else you can convince me you might need…..!

What’s next? You have the rest of this class, plus the next period, to design and conduct your experiment. You need my approval to move from the design phase to actual testing. EVERYTHING will be written up in you lab notebook. Use the AP Bio Lab Rubric to help guide your official write up. Make sure to answer all of the following questions in your conclusion when finished.

Questions to answer: Summarize your experiment. Were some of your initial assumptions as to which type of molecule was in each food confirmed or denied? Explain. How did you test each compound for simple and/or complex sugars? Explain. Describe the purpose of having a control for each test. What might have been some sources of error during your experimentation? Explain.