Enzymes (page 2)
Try New Approaches
How does pH affect proteases in detergent? Repeat the experiment with the hard-boiled eggs, omitting detergents without enzymes. Instead, have four sets of three jars. For each set 1, label and number the jars "Control-1," "Acid-1," and "Base-1." Fill the jars with distilled water as before. Add 1 tablespoon (15 ml) of detergent with enzymes to jars Acid-1 and Base-1. Use red and blue litmus to test the water in each jar. In the Base-1 jar, if necessary, add 1 teaspoon (5 ml) baking soda at a time so that the pH is high enough to turn the red litmus blue. In the Acid-1 jar, if necessary, add 1 teaspoon (5 ml) of vinegar at a time until the pH is low enough to turn blue litmus red. Repeat preparing sets 2, 3, and 4, then proceed as in the earlier experiment. Note: Litmus can be obtained at most teacher supply stores or your teacher can order it from a science supply company. See Appendix 9 for a list of science supply companies.
Design Your Own Experiment
Does temperature affect detergent enzymes? Design an experiment to determine how the temperature of wash water affects stain removal. One way is to use a permanent marker to label twelve 4-inch (10-cm) squares of white cotton cloth. Label 4 pieces "Cold," 4 pieces "Warm" and 4 pieces "Hot." Stain each by placing 1⁄8 teaspoon (0.72 ml) of yellow mustard in the center of each cloth. Spread the mustard and allow it to dry. Prepare four sets of three 1-pint jars with lids. Each set will contain jars with cold distilled water, warm distilled water, and hot distilled water. Add 1 tablespoon (15 ml) of detergent with enzymes and 1 stained cloth to each jar of water. With the lids secured on each jar, vigorously shake each jar 5 times every 15 minutes for 1 hour. Then remove the cloth pieces, rinse in cold tap water, and allow to dry. Compare the stains. The cloth pieces in the warm water will be used as a control to compare with the cloth pieces in cold and hot water.
Get the Facts
- The term detergent applies to materials that aid in the removal of dirt or other foreign matter from soiled items. Soap was the main detergent until the 1940s, when synthetic detergents were first developed. Now the term soap is usually used to refer to a cleanser made primarily from fat or oil, which doesn't clean well in hard water. Detergent is not made with fat or oil and is chemically active even in hard water. Find out more about the differences and similarities between soaps and detergents. Why are they called surfactants? Explain the hydrophilic and hydrophobic structures of each and how these structures aid them in cleaning. For information, see Carl H. Snyder's The Extraordinary Chemistry of Ordinary Things (New York: Wiley, 1997), pp. 323–329.
- Discover more about the biochemistry of specific enzymes and the proteins they break down. One model that you could use to represent the specific nature of enzymes is the lock-and-key example. Each key fits only one lock, just as each enzyme "fits," or reacts with, only one protein, or a specific class of proteins. Information about the lock-andkey model can be found in a biology textbook.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.