FlinnPREP™ Inquiry Labs for AP® Biology: Peroxidase Enzyme Activity

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Big Idea 4, Investigation 13

Enzyme activity—how the rate of an enzyme-catalyzed reaction depends on concentration, pH, temperature, metal ions, etc.—provides the central basis for understanding how enzymes function. Among the thousands of different enzymes in a single cell, peroxidases are among the most active and the most widely distributed. Peroxidases protect plants and animals against cell damage by catalyzing the breakdown of hydrogen peroxide, a natural but toxic byproduct of aerobic respiration. In this Flinn Inquiry Lab Kit, students investigate the activity of turnip peroxidase by measuring its rate of reaction with hydrogen peroxide and a natural reducing agent called guaiacol.

The Inquiry Lab Kit begins with a Baseline Activity. Students use a Flinn Spectrophotometer or Vernier SpectroVis Plus to measure the absorbance of the orange product formed from the peroxidasecatalyzed reaction of guaiacol and hydrogen peroxide as a function of time. Graphical analysis gives the rate of the reaction—and the first clue for a model of enzyme action. Using this general procedure, students continue in the Opportunities for Inquiry portion of the lab to design experiments in search of additional evidence that may support or refute the mechanism of enzyme action. What does substrate concentration reveal about enzyme-substrate binding? How does the effect of pH illustrate the essential nature of protein and enzyme structure?

Includes detailed teacher notes, reproducible student handouts and enough materials for eight groups of students to complete the Baseline Activity and additional inquiry activities, including the variable discussed. A blender and spectrophotometer are required and available separately. Fresh turnips are also required.