Featured in PASCO’s Advanced Biology through Inquiry Teacher Guide
This manual features 22 challenging, standards-based, inquiry lab activities for AP, IB, and honors programs.
Students use an oxygen gas sensor or pressure sensor to investigate the catalyzed decomposition of hydrogen peroxide by catalase.
Enzymes are proteins that catalyze chemical reactions by reducing the reaction’s activation energy, This is important in many reactions. For example, to digest lactose (a sugar found in milk), lactase must be present. People born without the gene to produce the enzyme lactase cannot digest lactose.
Enzymes are hyper-specific—often an enzyme interacts with only one substrate. Like catalysts in other chemical reactions, enzymes are not consumed during the reaction but help turn the substrate into the final product. Notice in the following reaction that the enzyme is present before and after the reaction.
enzyme(l) + 2H2O2(l) → 2H2O(l) + O2(g) + enzyme(l)
Hydrogen peroxide (H2O2) is a byproduct of aerobic respiration in cells and is used in cell signaling and apoptosis. Hydrogen peroxide is highly reactive and can produce free radicals that damage nucleic acids, so cells must carefully regulate its concentration. To remove excess hydrogen peroxide, cells produce an enzyme (called catalase in animal cells and peroxidase
in plant cells) which breaks down H2O2 into oxygen (O2) and water (H2O), as shown above. This reaction proceeds spontaneously without the enzymes at a very slow rate. This uncatalyzed reaction will serve as the baseline, or control, in the initial investigation.
Students investigate the catalyzed decomposition of hydrogen peroxide by catalase or peroxidase according to the equation: enzyme(l) + 2H2O2(l) → 2H2O(l) + O2(g) + enzyme(l) Students can use either the oxygen gas sensor or pressure sensor to measure the oxygen gas produced as the reaction proceeds. Students design an experiment to investigate questions they devise about factors that can affect catalyzed reaction rates. Investigations that manipulate pH, temperature, enzyme concentration, or substrate concentration work well.
This experiment may require software and an interface for data collection.