Mellon/ MCHS
Biochemistry Lab—A Case of Possible Food Poisoning
You are a Medical Technician at a local hospital. Four college students have been admitted to the
emergency room in the last ten hours complaining of stomach pain, vomiting, and high fever.
Because these people ate at the same cafeteria, this may be a case of food poisoning. Your job is to
test the lab specimens (vomit) and make a report on the following:
1. What did each person consume? (carbohydrate—sugar or starch, fat, or protein)
2. Do your results show any similarities between the four patients?
Because of possible legal issues with the cafeteria (some patients may sue the restaurant if it turns
out to be food poisoning), ALL of your methods and results must be succinctly and thoroughly
reported.
Follow this format in your lab write-up:
1. Title
2. Purpose
3. Hypothesis
4. Procedure: Each person in the lab group writes up procedures for all tests! The 4
molecules are: simple sugars, starch, lipids, and proteins.
a. Describe these 4 molecules (what they are, give examples, chemical makeup)
b. Write out the testing procedure for these molecules (See back)
c. Do the chemical tests and remember to include a positive and negative control. (You
can split the work at your table if you show everyone at your table your test tube
results)
The four tests are: simple sugar, starch, lipid, and protein.
5. Data table: Copy example:
Simple Sugar Test
Starch Test
Lipid Test
Protein Test
Tube
#
Contents
1
3
Negative
control
Positive
control
Mr. Doe
4
Ms. Rae
5
Mr. Mi
6
Ms. Fa
2
Initial
Color
Final
Color
(+) or
(-)
Final
Color
(+) or
(-)
Final
Color
(+) or
(-)
Final
Color
(+) or
(-)
6. Analysis of Results in sentences: Explain how you know your results were positive or
negative in each of the four tests (refer to your control results!)
7. Conclusion: Did you prove or disprove your hypothesis? Answer the two questions in the
box above. Was this a case of food poisoning? What molecule did they have in common?
What food could be? Include Analysis of Errors. Describe any errors of experiment and
why your results were altered or could have been altered.
Mellon/ MCHS
Simple Sugar test:
1. Put 200ml tap water into a 600ml beaker. Put it on a hot plate and bring
the water to boil.
2. Label 6 test tubes #1-#6.
3. Shake each solution before you get your sample! Pipet 1ml of the
correct solution into it’s corresponding test tube. (Be sure to use the
correct positive control for #2)
4. Add 0.5 ml Benedict’s solution to each test tube and shake. Record this
initial color.
5. Heat the tubes in boiling water for 3 minutes. Remove the tubes with a
test tube clamp.
6. Record the final color. Distinguish between positive and negative results.
Starch test:
1. Label 6 test tubes #1-#6.
2. Shake each solution before you get your sample! Pipet 1ml of the
correct solution into it’s corresponding test tube. (Be sure to use the correct
positive control for #2)
3. Add 5-10 drops Iodine solution to each test tube and shake.
4. Record the final color. Distinguish between positive and negative results.
Lipid test:
1. Label 6 test tubes #1-#6.
2. Pipet 2ml water into each tube.
3. Shake each solution before you get your sample! Pipet 1ml of the
correct solution into it’s corresponding test tube. (Be sure to use the correct
positive control for #2)
4. Add 5 drops Sudan solution to each test tube and shake.
5. Record the final color. Distinguish between positive and negative results.
Pay attention to the lipid layer on the top!
Protein test:
1. Label 6 test tubes #1-#6.
2. Shake each solution before you get your sample! Pipet 1ml of the
correct solution into it’s corresponding test tube. (Be sure to use the correct
positive control for #2)
3. Add 0.5ml Biuret solution to each test tube and shake.
4. Record the final color. Distinguish between positive and negative results.
Food served in the cafeteria: Steamed Chicken with Herbs, Salad with oil and vinegar dressing,
Rolls, Butter, Fruit & Jello Salad.
Mellon/ MCHS
Biochemistry Lab Teacher’s Notes:
Summary: Students will describe the differences between biochemical molecules, know that these
molecules are found in the food we eat, and use the appropriate biochemical tests to determine the
presence or absence of these molecules. The importance of positive and negative controls should
also be discussed.
California State Standards:
Cell Biology: 1h
Investigation and Experimentation: 1a, b, c, d, j
Materials and Equipment:
Per student group (4)
Marker
Test tube clamp
600ml beaker
24 test tubes
4 test tube racks
100ml beaker with water
vortex mixer (optional)
Stock solutions (Make a few sets and put them in accessible areas in the room)
Put the following in dropper bottles or have a small disposable graduated pipet available:
Benedict’s Solution for Sugar test
Lugol’s Iodine for Starch test
Biuret for Protein test
Sudan IV for Lipid test
Put the following in bottles or beakers and have a pipet/pipet pump available:
Negative control: Water
Positive control: Sugar (10% dextrose)
Positive control: Starch (10% soluble starch)
Positive control: Protein (use 10% egg albumin)
Positive control: Lipid (use 100% vegetable oil or mineral oil)
To make the “vomit” samples, mix together positive controls in equal amounts:
Doe: protein, starch, lipid
Rae: protein, starch, sugar
Mi: protein, starch, sugar
Fa: protein, protein, lipid
Note: Lipid will rise to the top of the solution… remind students they must mix all samples before
pipeting out 1ml