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What’s in it?
A Macromolecule Testing Lab
Name: ____________________
period & date: _____________
Purpose: To analyze a substance for the presence of complex carbs, simple sugars, proteins, &
lipids
Background: Bob Glucom claims he has developed a tasty new drink suitable for diabetics. Qualbev
Inc. is very interested in marketing this beverage, but Mr. Glucom refuses to give out
the secret recipe before they sign the deal. However, Qualbev Inc. needs to make sure
this drink is safe for diabetics (meaning it cannot contain any sugar). Your job as a
food chemist for Qualbev is to test the beverage for simple sugars as well as protein,
complex carbs (starch), and lipids. Of the 2 unknown solutions, one is Mr. Glucom’s
beverage and one is not.
Materials: unknown solution A, unknown B, starch solution, gelatin solution, vegetable oil, glucose
solution, Benedict’s reagent, biuret reagent, soap, test tubes, test tube holders, Lugol’s
iodine, hot plate(s), pipettes, Barnes bottles for reagents, beakers, water, GOGGLES!!!,
tape to label test tubes, 4 stations for each type of testing with example + & - test tubes,
test tube brushes, Petri dishes, brown paper bag or similar paper
Procedure:
1.
2.
3.
4.
5.
6.
7.
Part 1: Simple Sugars
Label one test tube “A” and another “B.”
Add 5-10 drops of unknown solution A to tube A and 5-10 drops of unknown solution B to
tube B.
Add 5 drops of Benedict’s reagent to tubes A & B.
Place the test tubes in the beaker of boiling water and wait 1-2 minutes.
Remove tubes with test tube holders and compare with sample + & - test tubes. A positive
test will be yellow or orange. A negative test will remain blue.
Record results in TABLE 1 in the results section.
Rinse the test tubes. If a tube will not rinse clean, dispose of it in the broken glass disposal
bucket. Tubes that rinse clean can be reused. BE SURE THEY ARE CLEAN TO PREVENT
CONTAMINATION OF YOUR RESULTS!!!
Part 2: Protein
1. Label one test tube “A” and another “B.”
2. Place 10 drops of unknown solution A into test tube A and 10 drops of unknown solution B
into test tube B. Proceed to station 2: proteins.
3. Add 10 drops of biuret reagent to both tubes A and B.
4. Compare with the sample + & - test tubes. A positive test for protein will be lavender, violet
or pink. A negative test will remain about the color of the biuret.
5. Record you results in TABLE 1 in the results section.
6. Rinse the test tubes. If a tube will not rinse clean, dispose of it in the broken glass disposal
bucket. Tubes that rinse clean can be reused. BE SURE THEY ARE CLEAN TO PREVENT
CONTAMINATION OF YOUR RESULTS!!!
Part 3: Complex Carbs (starch)
1. Go to station 3: complex carbs.
2. Label one side of a Petri dish “A” and one side “B.”
3. Place a drop of unknown solution A on the A side and a drop of unknown solution B on the
B side.
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4. Add 1 drop of Lugol’s iodine to A & B.
5. Compare with the sample + & - example provided. A positive test for starch will turn a
bluish-black color. The negative result will remain a rusty color (just like the iodine)
6. Record your results in TABLE 1 in the results section.
7. Rinse the Petri dish thoroughly, dry it, and return it to the basket.
Part 4: Lipids
1. Go to station 4: lipids.
2. Cut 2 small squares of brown paper big enough to fit a quarter on. Label one “A” and the
other “B.”
3. Return to the location of the unknown solutions A & B and place a few drops of each on the
corresponding piece of brown paper.
4. Return to station 4: lipids.
5. Compare with the + & - sample provided. Hold each up to the light. If lipids are present,
the paper will appear translucent. In the absence of lipids, the paper will still appear opaque
and just look wet.
6. Record your results in TABLE 1 in the results section.
7. Throw your paper squares in the trash.
Results:
A
color/result
B
+ or -
color/result
+ or -
Station 1: simple sugars
Station 2: proteins
Station 3: complex carbs
(starch)
Station 4: lipids
Conclusions:
1. Which unknown solution (if any) would be safe for diabetics? How do you know this?
2. Is Mr. Glucom’s claim correct? Explain your answer.
3. Which substances does each beverage contain?
AB4. Which beverage (if any) would you recommend for someone on a low-carb diet? Why?
5. Can your data tell you how much of these substances (sugars, protein, etc.) are in the
beverages? Why or why not? Clarify the difference between QUALITATIVE and
QUANTITATIVE data.
6. What would you have to do to make a nutrition label for one of these beverages?