3. Testing for Life - Sources

All the materials needed for this lab may be purchased from Flinn Scientific or other science supply companies.

  • Protein test - Biuret solution (Flinn Scientific catalog #B0050, $4 for 100 ml) an alternative test for protein uses Ninhydrin solution (Flinn Scientific catalog #N0039, $9.50 for 100 ml)
  • Glucose test - Benedict’s solution (Flinn Scientific catalog #B0171, $3.50 for 100 ml qualitative solution and #B0172, $5 for 100 ml quantitative solution) an alternative test for glucose that does not require the hot water bath is to use glucose test strips that can be purchased from the pharmacy for diabetic urine testing (approximately $15-20 for a bottle of 100 strips, double your supply by cutting each strip lengthwise)
  • Starch test – iodine tincture (purchase from your local pharmacy or Flinn Scientific catalog #I0009, $5 for 100 ml)
  • Positive control for glucose test – either use glucose solution (Flinn Scientific catalog #G0024, $7.75 for 100 ml) or dissolve glucose tablets for diabetics in water (purchase from your local pharmacy)

Unfortunately, the common tests for nucleic acids, such as the Dische test, are highly toxic (the Dische test solution is dissolved in 2M sulfuric acid) and is not ideal for use in a middle school classroom.

Testing for organic molecules is a common activity in biochemistry classes. The following are some of the resources available:

  • Mission 10 from the Life in the Universe curriculum, published by the SETI Institute provides great ideas and information about how to teach about organic molecules, particularly carbohydrates and proteins, to students.
  • William Monaco of Pennsylvania State University provides an excellent description of lab to test for the presence of proteins, carbohydrates, and lipids.
  • Michael Gregory of Clinton Community College also includes a full write up with excellent pictures of this lab.
  • Anthony Huntley of Saddleback College describes a similar lab including the Dische test for nucleic acids as well as a good series of conclusion questions (see Week 3’s Biologically Important Molecules lab).

Grade 8
Chemistry of Living Systems (Life Sciences)
6. Principles of chemistry underlie the functioning of biological systems. As a basis for understanding this concept:
a. Students know that carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organisms.
b. Students know that living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.       
c. Students know that living organisms have many different kinds of molecules, including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.

Grades 9-12 Biology
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a small collection of simple precursors.

Grades 9-12 Chemistry
Organic Chemistry and Biochemistry
10. The bonding characteristics of carbon allow the formation of many different organic molecules of varied sizes, shapes, and chemical properties and provide the biochemical basis of life. As a basis for understanding this concept:
a. Students know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.
b. Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.
c. Students know amino acids are the building blocks of proteins.