Title: Who done it?  A criminal investigation using indicator tests.

Topic:  Indictor testing for the presence of protein, carbohydrates, and lipids.

Grade Level: Living Environment

Time: 80 minute double period.

                        First period- lecture

                        Second period- lab

Science background material for the teacher:  All living things contain organic macromolecules: lipids, proteins, carbohydrates, and nucleic acids.  Each of these macromolecules contain building blocks:


Building Block


Amino Acids




Glycerol + Fatty Acids

Nucleic Acids


Testing for macromolecules:



Change Observed

Carbohydrates (test for the presence of starch)

Lugol’s reagent (iodine solution)

Changes from yellowish-brown to a dark purple/black


Brown paper towel

Paper towel becomes translucent in the presence of lipids (grease/fat)


Buiret solution

Buiret solution changes from a blue liquid to purple (lavender) when proteins are present.

Indicator: a substance that undergoes a distinct observable change when condition in its solution change.  It indicates the presence or absence of a particular substance.

Objectives: At the end of this lesson students will be able to:

1.      Name the four biological macromolecules and their building blocks.

2.      Test food samples for the presence of lipids, proteins, and carbohydrates.

3.      Use proper laboratory techniques to complete indicator tests.

4.      Apply knowledge of indicators to solve a murder mystery.

National Science Education Standards:

1.     Use technology and mathematics to improve investigations and communications.

2.     Formulate and revise scientific explanations and models using logic and evidence.

3.     Cells have particular structures that underlie their function.

4.     The atoms and molecules on the earth cycle among the living and nonliving components of the biosphere.

New York State Living Environment Core Curriculum Standards:

2.2a Development of a research plan involves researching background information and understanding the major concepts in the area being investigated. Recommendations for methodologies, use of technologies, proper equipment, and safety precautions should also be included.

1.2hMany organic and inorganic substances dissolved in cells allow necessary chemical reactions to take place in order to maintain life. Large organic food molecules such as proteins and starches must initially be broken down (digested to amino acids and simple sugars respectively), in order to enter cells. Once nutrients enter a cell, the cell will use them as building blocks in the synthesis of compounds necessary for life.


40 1mL pipettes

40 medium test tubes

Lugol’s iodine solution

Buiret’s solution

1-package brown paper towels

500mL yogurt/water solution

500 mL milk/water solution

500 mL blended meat/water solution

500 mL corn starch/water solution

500 mL bread/water solution

Vegetable oil

Water (to act as control)

Computer (for teacher)

Projector/Smart Board (for teacher)

Who Done it? Video

Indicator solution Video

Power point

Motivation:  Bring in various food products.  Have the students identify what macromolecule the food is made of.  Apple- carbohydrates.  Milk- protein. Yogurt- protein. Bread- carbohydrates. Oil- lipids

Do Now: Think, Pair, Share: What do you think an indicator is? Indicator: a substance that undergoes a distinct observable change when condition in its solution change.  It indicates the presence or absence of a particular substance.


1.    Continue the discussion from the do now of what an indicator solution is.  Ask the students if they know any other indicator solutions (such as cabbage juice as a pH indicator. 

2.    Show the “Indicator Video.”  This video explains the 3 indicator tests we will be performing today.

3.    Review the video.  Ask: How do you test for a carbohydrate in the solution?  Answer: use lugol’s iodine solution.  Ask:  What color does the iodine solution turn in the presence of carbohydrates? Answer: turn from a yellow brown to a blue black.  Continue this questioning for all three tests (use the table above to see the answers).

4.    We will now show a video of a murder mystery.  Your task: determine who the culprit is (who done it?)

5.    Have the students write down who murderer is.  Collect the answers and see if the majority of the class got the answer correct. 

6.    Discuss with the class why French fry is the murderer.  What should he be sentenced to?

7.    Move into lab. Review and discuss safety procedures.  Never eat anything in the lab.  No food or drink in the lab.  Wear eye goggles, hand protection, and an apron while in the lab.  No roughhousing.  Keep aisles clear of bags and books.

8.    The teacher will have testing stations set up.  The students will work in groups of 3.  They will have 5 minutes at each station to complete indicator testing.

a.    Station 1- yogurt/water solution

b.    Station 2- corn starch/water solution

c.    Station 3- plain water

d.    Station 4- oil

e.    Station 5- bread/water solution

f.     Station 6- meat/water solution

9.    Students will complete a portion of a worksheet at each station.  They will perform all 3 tests at each station to determine what macromolecule is present in the solution.

10. Closure: Go over the worksheet with the entire class.  Answer any questions or misconceptions.  Have students hand in their worksheet as class work.

Adaptations for students with disabilities: The lab area will be easily accessible for students with physical disabilities.  This includes setting up the stations in a manner that the students can easily and safely rotate around.  The use of a murder mystery in the beginning of the lesson will keep the attention of students with a general learning disability.  Laptops and headphones will be made available for students that need to watch the videos at their own pace or re-watch the video to understand the material.

Multicultural Connections: Throughout out our discussion on macromolecules and different food groups the teacher can encourage students to share foods from back home that we may not have here and its food group.

Technology Incorporation:  The teacher will use the projector and a saved movie to motivate the students.  The teacher can also use the Smart Document Camera to display student work when going over the worksheet.

Assessment:  Students will be assessed based on the completion of their work in the lab and the worksheet they hand in will be graded.  They will also be given homework to complete on building blocks, macromolecules, and indicator testing.

Extension Activities: Students can be given a research activity on the different indicator tests (such as cabbage juice as an indicator for pH).