Macromolecules, part 2-Murder and a Meal

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Students will plan a procedure for the identification of nutrients in food samples.

Big Idea

Case studies are a fun way to learn science.


5 minutes

Warm-Up: “If an unknown substance found on a meteorite is determined to contain no trace of carbon, can scientists conclude that there is no life wherever the meteorite came from?”  Explain your answer.

This question serves as a review of the previous lesson, Macromolecules, part 1.  It requires students to not only recall facts but it also requires them to explain the “why” of their response, which allows them to practice higher order thinking.

Allow students to ponder the question for several seconds before accepting students’ ideas.  Giving students ample time to consider a question allows all learners to have adequate time to consider the question and possible responses.  After a short period of thinking time, allow 2-4 students to share their thoughts. 

Encourage students to engage in academic discourse for 2-3 minutes using the academic sentence prompts. Look for students to identify that carbon is a biological component of almost all life and life as we know it, is carbon-based.  Therefore, we can assume that that there is no life where this meteor originated from.

Content Review

20 minutes

Distribute an envelope or small sandwich bag of macromolecule labels and terms to groups of two students.  Because my students sit in pairs at lab tables, is easier to have students work with their seatmate for this activity. Tell students to not open the bag until told to do so. Note: Use the Macro matching template to make enough sets of the labels and terms for students.

Explain that this activity is a matching activity that will allow students to reinforce the concepts taught in the previous lesson.  Project instructions for visual learners as you explain how to complete the performance task. Explain that the envelope contains the four large macromolecule labels and several other terms on smaller pieces of paper. Instruct students to categorize the terms into one of the four macromolecule groups.

After providing the instructions for the task, display a timer and set it for 5 minutes Release the groups to match each of macromolecule headers with the terms in the envelope. Walk around the room to observe students at work to assess how easily or difficult they find this task. Listen to the table conversations, as well.  Note misconceptions and errors that should be addressed after the timed period ends and the class reviews the correct associations between the terms and the macromolecules.

After 5 minutes have passed, ask groups to stop their work.  Tell students that they will now participate in a carousel review.  A carousel review process involves students conducting peer review by rotating to the another table to review another group’s work. Explain how students will move from one table to another for the carousel review. The movement can be clockwise, backward, forward, etc.. based on the organization of the room.  Whatever the room set-up, it’s important to be explicit about how and what movement looks like before you direct students to move.  Being explicit with instructions about movement eliminates disruption.  It’s also a good idea to choreograph the start of movement by counting down, “3-2-1, move”.  This simple act allows for coordinated movement with minimal disruption, as well.

Guided Practice

10 minutes

Inform students that they will complete a Murder and a Meal in Clayton County case study that will allow them to plan an experiment to identify the nutrients found in food eaten by a victim of homicide (Note: Adapted from “Murder and a Meal” by Camron J. Stanley 2008).

Explain that students will work in groups of four on the assignment.  Prior to class, decide whether students will be allowed to form their own small groups or whether the groups will be pre-assigned.  Knowledge of your students and the class dynamics are valuable information that should be considered in making this decision.

Note: You may choose to change the names of the restaurants to reflect local establishments that students know well.  Familiarity with the restaurants may help build interest in the task.

Use the LCD projector to display an overview of the Murder and a Meal case study and provide hard copies of the instructions to each group, as well.  Ask for a student volunteer to read to case overview. Explain what students will be required to complete in their groups:

  1. Students must conduct research to determine the procedure to be used to test for each organic macromolecule (lipids, proteins, carbohydrates (glucose), carbohydrates (starches).
  2. Using information gathered from the research; write out the procedure for testing for each of the macromolecules. For each macromolecule you must (1) describe the procedure you will follow to perform each test.  This should be detailed enough so that anyone can follow the procedure.
  3. Describe how a positive result for the macromolecule will look, and describe how a negative result for the presence of the macromolecule will look.

Provide access to computers and display a list of useful sites that will help in the completion of the assignment:

Model how a procedure should be written so that students will know how an exemplar procedure is written.  The example does not have to be scientific.  Just make sure that the procedure is detailed enough to display how procedures are written in the sequential order of the occurrence of actions.

For example, use the  “think aloud” strategy to model how to write a procedure for getting ready for school.  This will help students gain a better sense of how they should write the nutrient testing procedures:

  1. Get out of bed.
  2. Brush your teeth and wash your face.
  3. Eat breakfast.
  4. Walk to the bus stop.
  5. Get on the bus.

Build a few errors and correct them.  For example, omit step 4 and go from step 3 to step 5.  Then, say, “Wait, have I explained how I went from eating breakfast to getting on the bus?  I think I forgot a step of the procedure.”  This type of modeling will help students observe how thinking occurs when writing a procedure.


Independent Practice

25 minutes

Release students to work on the assignments. Make sure that each student assumes responsibility for researching one of the four macromolecules.  Walk around to monitor that all students are on task and able to access the websites.

Walk around the room to monitor students work and ensure that all students are actively engaged in the completion of the task.

Instruct those students who are different learners or lower level readers to use the Identifying Nutrients gizmo from the previous lesson, Macromolecules, part 1 as the sole source of information for the assignment, while requiring other students to access the websites for information.

The identifying nutrients lab was utilized in the previous lesson and it is very informative and useful in understanding the procedures for the identification of macromolecules.  The assignment of how information is accessed allows all students to contribute to the group work, while learning the information in a manner that is better suited to a particular learning style or challenge.

The student work samples show that students were able to identify how to test for the presence of different molecules.  However, the quality of the written procedures varied, even within the same submitted work for a group.  Student work 1 shows that the students in the group were able to write a sequential procedure for identifying nutrients but they did not include details about a negative test.  Student work 2 shows that the group provided more complete procedures for the positive and negative testing.




5 minutes

As a class, view hypothetical data and determine where the victim had his/her last meal. 

Look for students to be able to apply what they've learned about positive and negative testing to a food sample findings in order to justify their response.