Name______Block______

The Case: A murder has occurred right here in our peaceful little town of Marietta. As top-notch biology students at Wheeler 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 was performed on the victim and 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:

Saporito’s Pizza: The victim would never eat thin crust pizza from anywhere else! The victim would typically order a pizza with sausage, pepperoni, and bacon.

  1. Prediction: What two macromolecules would you most expect to find in the stomach contents of the victim if his last meal was eaten here?

Buffalo Wild Wings: The victim would hang out here to watch sporting events while feasting on Wingfest wings and celery.

  1. Prediction: What two macromolecules would you most expect to find in the stomach contents of the victim if his last meal was eaten here?

Frankie's Italian Restaurant: The victim loved to go here for a night of bread, olive oil, and buttery and creamy pasta.

  1. Prediction: What two macromolecules would you most expect to find in the stomach contents of the victim if his last 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, and who he had it with. The following suspects submitted the testimonies below.

Suspect #1 = The victim’s boss, who claims to have been out that night with coworkers at Fat Baby’s Pizza.

Suspect #2= The victim’s roommate and best friend, who claims to have been out with their other buddies at the Smokehouse, eating wings and watching the Clemson game.

Suspect #3 = The victim’s girlfriend, who claims to have been out at Frankie Bones that night with her parents who were in town.

  1. Hypothesis = Who do you believe the killer is?

How to Test: Before analyzing the stomach contents of the deceased, you must determine the procedure usedto test for the presence of each macromolecule. Read the information provided below.

Use this informationto complete Table 1 on the next page with the name of the test to be used and what a positive and negativeresults will appear to beBEFORE doing the tests.

The Tests:

Simple Sugar Test: Benedict’s Solution

In the presence of simple sugars, the clear blue solution turns green, yellow, or brick red.

1. Add 40 drops of sample to a test tube.

2. Add 10 drops of Benedict’s solution to test tube.

3. Heat in hot water bath at 40-50 degrees Celsius for 5 minutes.

4. Note color change.

Complex Sugar (Starch) Test: Lugol’s Iodine Solution

In the presence of starches, the solution will turn bluish/purple-ish black.

1. Add about 40 drops of sample to the test tube.

2. Add 3-4 drops of iodine.

3. Note color change.

Protein Test: Biuret Solution

In the presence of proteins, this blue solution will change color to pink-purple.

1. Add 40 drops of liquid to be tested to a test tube.

2. Add 10 drops of Biuret Solution to test tube. Cover with thumb and shake gently to mix.

3. Note any color change.

Lipid Test: Sudan III Stain

In the presence of lipids, fat cells will turn red and form a fatty layer on top of liquid’s surface.

1. Fill a quarter of the test tube with the sample. Fill another quarter of the test tube with water. The test tube should be half full.

2. Add 6 drops of Sudan III stain to test tube. Cover with thumb and shake gently. Let sit.

3. A red-stained oil layer will separate out and float on the water surface if fat is present.

Procedures: After reading about the different tests and filling in Table 1, you will need to obtain a sample from the crime scene. Dilute the sample in a beaker of water 50:50 (if your teacher hasn’t already done so.)

Use this diluted sample for each of the tests above. Record results in Table 2, then complete the analysis and conclusion.

Data

TABLE 1 – Positive and Negative Results

Macromolecule / Name of Test / Positive Test Result / Negative Test Result
Carbohydrates – Simple Sugars
Carbohydrates – Starch
Lipids
Proteins

TABLE 2 – Results for the presence of Macromolecules in the evidence sample

Test for Carbohydrates – Simple Sugars / Test for Carbohydrates – Starch / Test for Lipids / Test for Proteins
Observations:
Results:
Positive or Negative / Positive or Negative / Positive or Negative / Positive or Negative

Analysis:

1. Based on the data you’ve collected, what foods were present in the stomach contents of the victim? Where do you suppose the victim last ate based on this data?

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  1. What is the importance of having control groups for each test in this lab?

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  1. Why did we not test for the presence of nucleic acids in the stomach content of the victim? Explain.

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  1. Explain which suspect was most likely the killer, based on the data you collected from the evidence sample from the victim’s stomach. Include your reasoning based on what you know about macromolecules and what foods you normally find them in. Refer back to your hypothesis and whether your data causes you to support or reject it. Finally,describe three ways your knowledge of macromolecules could be applied to real worldsituations.

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Station 1

Simple Sugar Test: Benedict’s Solution

In the presence of simple sugars, the clear blue solution turns green, yellow, or brick red.

1. Add 40 drops of sample to a test tube.

2. Add 10 drops of Benedict’s solution to test tube.

3. Heat in hot water bath at 40-50 degrees Celsius for 5 minutes.

4. Note color change.

Station 2

Complex Sugar (Starch) Test: Lugol’s Iodine Solution

In the presence of starches, the solution will turn bluish/purple-ish black.

1. Add about 40 drops of sample to the test tube.

2. Add 3-4 drops of iodine.

3. Note color change.

Station 3

Protein Test: Biuret Solution

In the presence of proteins, this blue solution will change color to pink-purple.

1. Add 40 drops of liquid to be tested to a test tube.

2. Add 10 drops of Biuret Solution to test tube. Cover with thumb and shake gently to mix.

3. Note any color change.

Station 4

Lipid Test: Sudan III Stain

In the presence of lipids, fat cells will turn red and form a fatty layer on top of liquid’s surface.

1. Fill a quarter of the test tube with the sample. Fill another quarter of the test tube with water. The test tube should be half full.

2. Add 6 drops of Sudan III stain to test tube. Cover with thumb and shake gently. Let sit.

3. A red-stained oil layer will separate out and float on the water surface if fat is present.

Station 5

Control Groups

Sample Positive and

Negative Results for

each Test

Use these test tubes as references as you complete each test for the sample to determine a positive or negative presence of each macromolecule.