Name: _____________________________________________________________Date:____________
Due to your excellent background in biochemistry, you have been hired by Dr. Oliver Border of the
Lancaster County Medical Examiner’s Office to clear up a situation. During some confusion with previous
laboratory technicians, samples of stomach contents from 5 murder victims got mixed up! Since these
specimens will serve as evidence in pending murder trials, it is essential that this mistake be corrected. The
only information that you have about these murder victims is what their last meal was. Hopefully your
knowledge of biochemistry will enable you to fill in the gaps and you will be able to match different stomach
contents samples with their “owners”. You should follow the procedures (found on pages 2-3) for identifying
various organic molecules including monosaccharides, starch, lipids, and proteins. Information about the last
meals of the 5 victims is as follows:
NAME OF VICTIM
LAST MEAL
Wendell Sputz
A bag of Swedish fish and
a baked potato
Margaret Little
Pineapple and tea
U. R. Downs
Plain spaghetti noodles
Lucy Wunderchomper
Large salad with lots and
lots of dressing
Davis O’Leary
Two eggs with cheese
and OJ
PREDICT TYPE(S) OF MACROMOLECULE(S)
FOUND IN LAST MEAL
Set up the experiment to test the five stomach content samples using all 4 tests. The stomach contents have already
been labeled 1-5. Record your results in Table 1 and analyze your results to determine which stomach contents belong
to which murder victims. Put your conclusions in Table 2. GOOD LUCK!
MATERIALS
Safety goggles
Five test tubes
Test tube rack
Test tube holder
Benedict's solution
Iodine solution
Biuret solution
Spot well
Brown paper towel
Marker
Hot plate with hot water bath
Test tube brush
Soapy water for clean up
Stomach contents of 5 victims
MANDATORY: MAKE SURE YOUR GOGGLES ARE ON!
DIRECTIONS FOR LIPID (FAT) TESTING
Observation
1. Obtain a spot well and place 1 dropper full of each stomach content sample in separate large wells.
Decide which ones look greasy.
2. Obtain a piece of paper towel and drop a small drop of the stomach content sample on the towel. Leave
it dry during the class period. Toward the end of class, observe the spots that are left. Is there still a
spot left? Does it look greasy? Mark your results in your data table.
3. Throw away paper towel and use spot well samples for the starch test once done with lipids.
DIRECTIONS FOR CARBOHYDRATE TESTING
Part 1: Monosaccharide (Sugar) Testing - Benedict’s Reagent
1. Place 1 dropper full of each stomach content sample in the appropriately labeled test tube.
2. Place 10 drops of the Benedict's solution in each test tube.
3. Mix gently by swirling the test tube.
CAUTION: Benedict’s can cause irritation. If you get Benedict’s solution on your skin, wash it off immediately with
soapy water. Clean up any spills on lab top with soapy water.
4. Place the test tubes in the hot water bath and heat for up to 5 minutes.
5. Remove the test tubes with a test tube holder after changes have occurred and place in the test tube
rack until results are recorded.
CAREFUL: Tubes are hot!
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6. ANALYSIS: Benedict's solution turns from clear blue to a cloudy orange/red in the presence of a
monosaccharide. If there are small amounts of monosaccharide present, Benedict’s may turn green or
yellow.
7. Record results in the data table.
8. Clean the test tubes using a test tube brush and soapy water. Rinse well and place upside down on the
pegs on your test tube rack. Place entire rack on the paper towels.
Part 2: Starch Testing - Iodine
1. Use the spot well samples from the lipid test.
2. Place 5 drops of iodine solution into each well.
CAUTION: Iodine will stain your skin and clothes. If you get Iodine on your skin, wash it off immediately with soapy
water. Clean up any spills on lab top with soapy water.
3. ANALYSIS: The iodine solution will change from brown to a dark purple/black color in the presence of
starch.
4. Record the results in the data table.
5. Clean the spot well using a test tube brush and soapy water. Rinse well and place upside down on paper
towel.
DIRECTIONS FOR PROTEIN TESTING
Biuret Test
1. Place 1 dropper full of each of the stomach contents in the larger wells of the spot well.
2. Add 5 drops of Biuret solution into each well.
3.
CAUTION:
Biuret can cause irritation or skin burns. If you get Biuret solution on your skin, wash it off immediately
with soapy water. Clean up any spills on lab top with soapy water.
4. ANALYSIS: Biuret will change from light blue to purple in the presence of protein.
5. Record results in the data table.
6. Clean the spot wells with the brush and soapy water. Rinse well.
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RESULTS
TEST
Biomolecule
Observation
Lipids
(fats)
Benedict’s
Monosaccharide
(sugar)
Iodine
Starch
Biuret
Protein
Stomach
Contents 1
Stomach
Contents 2
Stomach
Contents 3
Stomach
Contents 4
Stomach
Contents 5
TABLE 1: Results of biomolecule tests for five different stomach contents. + indicates the sample is
positive for the biomolecule. – indicates the sample is negative for the biomolecule.
NAME OF VICTIM
LAST MEAL
Wendell Sputz
A bag of Swedish fish
and a baked potato
Margaret Little
A bag of Skittles and
iced tea
U. R. Downs
Plain spaghetti
noodles
Lucy Wunderchomper
Large salad with lots
and lots of dressing
Davis O’Leary
Two eggs with cheese
and OJ
NUMBER OF
STOMACH
CONTENTS
TABLE 2: Conclusions derived from analysis indicating the most probable
match between the victim and the stomach contents sample.
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CONCLUSION
To conclude this laboratory you will be analyzing your data and
presenting your data in the form of a lab report. Using the data you
obtained, you must conclude which stomach contents belong to
which victim and support yourself with your results.
Your lab report should include all of the essential components of any
good investigation. You should have an explanation of your original
hypothesis along with an introduction and background information
on macromolecules. All materials used should be included as well as
a detailed description of your methods. Results should be presented
in a table format and your discussion/ conclusion section should
explain your results and relate back to your hypothesis. Finally, you
will need to explain (based on your data) if the stomach contents
have been mixed up.
You lab report will be created using a wiki and only 1 report will
need to be submitted per lab group.
Outline of final lab report:
1. Introduction/ Background Information- be sure to include your
hypothesis
2. Materials
3. Methods
4. Results
5. Conclusion/Discussion
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