Enzymes in Action
You can use these easy and inexpensive labs to demonstrate enzyme activity.
By Lynsey Peterson
Chances are your students have heard of enzymes before they take your class. Unfortunately, they probably have no idea what they actually are. Many cleaners and products found in the marketplace tout their enzymatic action, and this is what students might be familiar with. But this is not the true function of enzymes. In our bodies, enzymes are essential. They are a special type of protein that are biological catalysts. Catalysts lower the activation energy of chemical reactions. Without enzymes, most cellular reactions would take too long for us to survive.
I introduce my students to the actions of enzymes with a simple demonstration laboratory. I dissolve some gelatin in warm water on a hotplate, and give each group of students two test tubes. In one test tube, students put meat tenderizer that has either pineapple or papaya extract. Some common enzymes found in meat tenderizer are Bromelian and Papain. These enzymes break down muscle fibers. I then pour a little gelatin in each test tube and students stir the contents and place the tubes in an ice bath. We take notes and discuss the characteristics of enzymes while the gelatin sets. After a few minutes, students check their test tubes. They find that the control gelatin set while the gelatin with meat tenderizer is still gooey. We discuss what happened and how it relates to enzymes.
We also show how enzymes are sensitive to environmental conditions. This is one reason why homeostasis is so important for our bodies. Changes in temperature or pH can denature enzymes and prevent them from functioning. My students illustrate this with a catalase lab. Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen gas. Without catalase, naturally occurring hydrogen peroxide could oxidize our cells. By placing small samples of raw and cooked tissue into test tubes of hydrogen peroxide, students can test the effect of temperature change on enzymes. I provide raw and cooked liver and potatoes for the students, as well as yeast. Students hypothesize which samples will show the most catalase activity and bubble the most. They are very impressed with the amount of bubbles that come from a little raw liver or yeast and the lack of activity from adding cooked tissue.
Using these labs really helps my students understand how enzymes work and helps break up some of the details they must also learn about these important organic compounds. You can try these and the ideas below to help your students understand the important role of enzymes.
Enzymes In Action:
Enzyme Activity: An Inquiry Based Approach
Students explore biochemical reactions mediated by enzymes in an inquiry approach. They are given two questions about the types of living materials that contain the enzymes that break down hydrogen peroxide, and under what conditions the enzyme works best.
Students test for the presence of enzymes in fruit and the specificity of those enzymes, as well as identify and show the susceptibility of enzymes to certain environmental factors (temperature and pH) originating in the enzyme's environment.
Students perform simple experiments to show properties of enzymes through studying how apple sauce can turn into apple juice and experimenting with papaya seeds. Students witness how enzymes speed up reactions through witnessing the breakdown of pectin and the resulting release of cell contents.
Students observe the actions of the enzyme and how shape is important to enzyme reactions.
Students explore the role of enzymes in chemical reactions. In this enzymes lesson plan, students use hydrogen peroxide and manganese dioxide to observe a chemical reaction. Students observe the rates of reactions of chalk, hamburger, liver, spinach, potato, and carrot with hydrogen peroxide. They use raw liver and boiled liver and compare the reactions. Students answer summary questions about their results and conclusions.
