Murder and a MealBiology 2011/12

The CaseA murder has occurred in the city of Fresno!

As top-notch biology students at Bullard High School, you have been asked to assist in the investigation of this most unfortunate incident. Central to identifying the individual who committed this crime is establishing where the victim was the day of the crime so that detectives can question the individuals with whom the victim came into contact.

• An autopsy that was performed on the victim has revealed that the victim ate just prior to the time of death. Upon questioning the victim’s friends and family, detectives working the case have learned that the victim enjoyed eating at the following places…

Review

• What are the four classes of macromolecules?

Hypothesis

• The next three slides will allow you to form a hypothesis

Me n’ Ed’s Pizzeria

The victim would never eat thin crust pizza from anywhere else! The victim would typically visit the local branch of Me and Ed’s and order a pizza with sausage, pepperoni, and bacon.

What macromolecules would you expect to find in the stomach contents of the victim if the victim’s final “pizza” was eaten here?

World Sports Cafe

The victim would hang out here to watch sporting events while feasting on Blazzin’ wings and celery.

What macromolecules would you expect to find in the stomach contents of the victim if the victim’s final meal was eaten here?

Ovidio’s Restaurante

The victim loved to go here for a night of bread, olive oil, and pasta.

What macromolecules would you expect to find in the stomach contents of the victim if the victim’s final meal was eaten here?

The forensic pathologist has removed the contents of the victim’s stomach for you to analyze in order to determine where the victim had his last meal.

Macromolecule

Chemical Test

Positive Test Result

Negative Test Result

Lipids(Wesson oil)

Proteins(tuna)

Carbohydrates-Glucose

(Karo syrup)

Carbohydrates-Starches

(rice)

Table 1. Positive and Negative Results for the Presence of Organic Macromolecules

Control Distilled WaterPaper Bag Benedict’s Biuret Iodine

Indicators

• 1. What is an indicator? How are indicators used in this experiment?

Lipid TestProcedure:1. Place a small scoop of the identified food onto the brown paper bag.2. With a paper towel, wipe off any excess pieces of food that may stick to the paper. 3. Set the paper aside - about 10 to 15 minutes.4. Hold the piece of brown paper bag up to a bright light or window.

Positive Result: Translucent spotNegative Result: Absence of Translucent spot

Carbohydrate (Starch) Test Procedure:1. Put one scoop of stomach contents

into well number one.2. Add 5 drops of Iodine stain to the test

tube.3. Gently stir with clean toothpick and

record any color changes.Positive Result: Contents will turn blue-black.Negative Result: Contents will remain yellow-brown.

Carbohydrate (Sugar) Test Procedure:1. Set-up a hot water bath. Half fill a beaker with

water and heat that water to a gentle boil.2. Put 2 scoops of the stomach contents into a test-

tube.3. Add 10 drops of Benedict’s solution to the test-

tube. 4. Gently shake the test-tube and place in the water

bath for 3 to 5 minutes.5. Use the test-tube holder to remove from the water

bath and place in the test-tube rack. Record any color changes.

Positive Result: Contents will turn yellow, orange, or red.Negative Result: Contents will turn blue.

Protein Test

Procedure:1. Put one scoop of the stomach contents

into well number 2.2. Add 5 drops of Biuret reagent to the test-

tube.3. Gently stir with clean toothpick and record

any color changes.Positive Result: Contents will turn blue-violet.Negative Result: Contents will remain blue.

Table 2. Results of investigation ______________________________________

Test for Lipids

Test for Proteins

Test for Glucose

Test for Starch

Observations: Observations: Observations: Observations:

Present? _______ Present? _______ Present? _______ Present? _______

Not Present? ____ Not Present? ____ Not Present? ____ Not Present? ____

Analysis 1. What is the purpose of using distilled

water as one of your test substances?2. Which macromolecules were found in the stomach contents?3. What were the indicators used in this lab?4. What is the purpose of an indicator?

5. If you wanted to test for the presence of amino acids what indicator would you use?

Conclusion

Use your data to explain in which restaurant your victim ate his last meal.

Extension

• Identify your favorite food.• What macromolecules do you think it

contains?• What indicators would you use to

support your hypothesis?