Name:_________________________________________________________        Per:_________        Date:______________

Murder and a Meal

The Case: A murder has occurred right here in our city of Portland, OR. As top-notch biology students at Cleveland 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 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.

Pyro Pizza

The victim would never eat wood fired pizza from anywhere else!  The victim would typically 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 “pie” was eaten here?

Fire on the Mountain

The victim would hang out here to watch sporting events while feasting on Blazin’ 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?

Kure Juice Bar

 The victim loved to go here for an afternoon of smoothies complete with an Orange boost blast. They would also often grab a bagel at Einstein Bros.

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

Background: Some of the biological macromolecules (“biomolecules”) the human body needs for energy, operation, and building materials are carbohydrates, proteins, fats & lipids, nucleic acids vitamins and salts. These biomolecules are present in the plants and animals humans use as food. These biomolecules are constructed primarily of carbon, hydrogen, oxygen, nitrogen, & phosphorus. All being very different in their shape however, they each have unique chemical properties. As a result, these bio-molecules react with certain chemical compounds (called indicator reagents) and produce different colors.  These colors allow us to know what biomolecule is present when mixed with a specific indicator reagent.  For example, when you add “Lugol’s iodine” to a solution containing starch the solution will turn a dark purple. 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. The powder has been dried for you to test.

Objectives:

In this investigation, the objectives are:

• To learn how to employ indicator reagents in a testing environment.
• To understand the use of indicator reagents in determining unknown, applicable substances.
• To understand the concepts of false positives and false negatives.

Materials:

• Safety goggles                 
• Benedict's solution
• Biuret solution                      
• indophenol solution
• Lugol’s iodine
• 1% silver nitrate (AgNO3)
• vortexer
• Scoopulas
• test tubes                
• glass stir rod
• hot water bath
• graduated pipettes
• known and unknown samples of biological molecules

Safety:

• GOGGLES MUST BE WORN AT ALL TIMES
• Tie back long hair
• The reagents you will use in this investigation may be corrosive, poisonous, irritating to the skin, may destroy clothing and stain anything.  Avoid skin and eye contact – if contact occurs, wash immediately
• Should a splash or spill occur, flush the area with plenty of water
• DO NOT mix the reagents
• Keep pipettes in their designated bottles

Procedure Day 1

Before analyzing the stomach contents of the deceased, you must master the procedure to be used to test for each organic macromolecule.  For each macromolecule you must (1) read the procedure you will follow to perform each test, (2) describe how a positive result for the macromolecule will look and record this information in Table 1, and (3) describe  how  a  negative  result  for  the  presence  of  the  macromolecule  will  look  and  record  this information in Table 1.

1. Negative Control: Mr. Shalman will test the distilled H2O (dH2O) we will be using in this investigation in order to determine if it is contaminated.  The results will be at the front of the room for you to record.
2. Positive Control: You will be testing known substances in order to learn the skill of using indicator reagents (i.e. Biurets solution, Lugol’s Iodine, etc.). Prepared is a data table to record your observations of the tests (Table 1).
3. Testing Protocol: For the following tests place a small (thumbnail) amount of the substance in the bottom of a test tube.  Add 3 mL of distilled water be sure to get the solid into solution.  To each of the known powders follow the protocol below.

1. Glucose: add 2 mL of Benedict’s solution; place test tube in hot water bath for ten minutes
2. Starch: add 5 drops of Lugol’s iodine solution
3. Vitamin C: add 3 drops of indophenol
4. Protein: add water, use vortexer to get protein into solution, add 1-2 drops of Biuret solution
5. Salt (in the form of NaCl): add 5 drops of silver nitrate (AgNO3)

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

Day 2 - The Investigation

The Investigation Part 1: Obtain a sample from the victim’s stomach and use that sample to answer the following questions before you begin your investigation.

1. What is the Investigative Question?

2. Identify the Independent & Dependent variables

Independent (what are you changing?):

        Dependent (what are you measuring?):

        Constants:

3.  What is your hypothesis? (If, then, because... statement)

4. Design a way to test what macromolecules this substance could contain. Write your protocol in the space below:

The Investigation Part 2: Below create a data table where you will collect information during your investigation of the unknown. Do not forget to include a title!

Analysis Questions

1. Describe why you chose the testing protocol you performed in order to determine what substances were in the unknown you received.

2. Through these testing protocols, make a conclusion as to what substances were present in the unknown sample given to your team and where the victim could have had their last meal.

3. How might the original colors of the test materials affect the results?

4. Explain the reasoning behind the negative control.  

1. Why was it done?

2. How does doing the negative control help eliminate false positives while testing the evidence?

5. Explain the reasoning behind the positive control.  

1. Why was it done?

2. How does doing the positive control help eliminate false negatives while testing the evidence?

6. Discuss how one could come to a conclusion which results in a false positive.

7. Discuss how one could come to a conclusion which results in a false negative.

Day 3 - Investigation Lab Write Up

Template for Murder and a Meal Lab

This is a template designed to help you understand what you need to include in your lab write up for the Murder and a Meal Lab.  Please delete the information and questions that I’ve provided after each section title after you are done answering them, but please leave the section titles.  Your report should address these requirements in 2-3 pages. The report must be typed and any diagrams, figures, or tables should be embedded into the document. Be sure to write in a persuasive style; you are trying to convince others that your claim is acceptable or valid!

TITLE

Background - This is the place to summarize what you have verified about the topic using research.  Use reputable online sources, but you can probably start with class notes, the lab handout, and text book.  You should have a minimum of two sources cited at the end of your report (No Wikipedia and MLA Citations).  You may repeat some of this information in your conclusion.  Please include information about biological macromolecules, what indicators are and what they test for, as well as what was the purpose of the lab.

(1/2 page maximum)

Investigative/Research Question – must be focused and not ambiguous in any way.  What is the effect of independent variable on dependent variable? Be specific. Example: How does the change in duration of exercise affect the rate of cellular respiration?

Hypothesis – state first & then give a logical rationale – your conclusion should address the hypothesis you are giving here.  Hypothesis should be in the form of an if, then, because statement. State the science behind your hypothesis explicitly and offer citations. Do some background research.

Variables – chart or list identifying Independent, Dependent, and Constant Variables (Level 4: Include in this chart how dependent variables will be measured, and how & why controlled variables will be controlled).

Data Analysis

Overview – this is a short paragraph section that gives an overview of your lab set up and what your data tables are showing. You should also provide an explanation of how and why you decided to present the data in the form that shows up later in this section.  This should show that you understand why you chose to analyze this way!

Testing with Knowns Data Table – Neatly lay-out and explain each of your chemical tests, what your negative test results should look like, and what your positive tests results should look like.

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

Testing with Unknown Data Table - Neatly lay out and explain the design for your second data table.

Insert *Table 2 here. ** Don’t forget the title!

Conclusion & Evaluation

Conclusion - this is a paragraph section in which you get a chance to discuss the results of your experiment. Write a conclusion that answers the investigative question in paragraph form:

• Answer your experimental question (CLAIM)
• Restate your hypothesis and describe if it was supported or not supported (do not use prove!)
• Briefly summarize your data and how is led you to determine if your hypothesis was supported or not supported (EVIDENCE)
• Explain your results using the data table that you made and how it led you to your conclusion (REASONING)
• Include references to background information to support your conclusion (2 citations minimum)

(1/2 page maximum)

Limitations of Experimental Design – this paragraph section discusses how well your experimental design helped answer your experimental question.  What worked well (and why) and what did not work well (and why).  This is also a section in which you should discuss why it was important to have a negative and positive control. You should also discuss why negative and positive controls help eliminate false negatives and false positives. Describe procedural errors and any limitations or observed mistakes that may have influenced your results. (1/2 page maximum)

Suggestions for Improvement - in reference to the limitations given in the previous subsection, what realistic and useful improvements could be made if you were to do this investigation again? How could you modify the procedure to ensure that you don’t get false positives or false negatives? (1/2 page maximum)