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Tips and Tricks for Success with Inquiry‑Based Enzyme Activities

Illustration of saccharomyces cerevisiae

Understanding enzyme action is a fundamental concept in biology. The “Testing Catalase Activity” investigation in our Investigating Biology through Inquiry book is a very popular activity for investigating enzyme action. Our O2 Gas Sensor and Gas Pressure Sensor can be used in this activity along with some very simple materials, such as yeast and hydrogen peroxide.

However, you can’t just mix hydrogen peroxide with a few drops of baker’s yeast and expect to get repeatable results every time. The amount of enzyme in a drop of yeast suspension depends on the number of yeast cells in each drop. This will depend on how long the yeast have grown and where the students pull each drop from the suspension. To get consistent results each time, the instructor must proof the yeast at least an hour in advance.

In addition, the suspension should be placed on a stir plate and students should pull samples from the middle of the suspension. Our resident biologists have revisited this experiment and found that purified catalase enzyme can be substituted for the yeast suspension in this exercise. This is an excellent option for investigating the effect of enzyme concentration. This is also a very cost-effective solution, as 1 g of catalase will provide enough enzyme for more than 4000 trials!

  • Purified catalase enzyme can be purchased from Flinn Scientific, Ward’s Natural Science, or Sigma-Aldrich. The concentration of enzyme varies from 2000–5000 units/mg and depends on the bottle.
  • You can mix up a stock solution of the enzyme in water. Make a stock solution of 1000 units/1 mL. For a step-by-step video on how to do this, visit Flinn’s website.
  • If you are using the O2 Gas Sensor for this investigation, use 0.5 mL (5 drops) of 1000 units/1 mL catalase solution for the preliminary activity. Add the enzyme to a 250 mL Nalgene bottle first, then add 10 mL of 3% H2O2. Start data collection immediately.
  • If you are using the Gas Pressure Sensor for this investigation, use 1 drop of 200 units/mL catalase for the preliminary activity. Add the enzyme to a 20 mL test tube or 15 mL conical tube first, then add 6 mL of 3% H2O2. Start data collection immediately.
  • If students are investigating enzyme concentration as an independent variable, make 100 units/mL, 1000 units/mL, and 2000 units/mL enzyme solutions.
  • If students are investigating substrate concentration, start with 6% H2O2 instead of 3% H2O2. This can be ordered from Flinn Scientific, Ward’s Natural Science, or Sigma-Aldrich.
  • Store the catalase powder as instructed. Enzyme activity may decrease from year to year, but will remain viable for up to three years.

By using these tips, you and your students will have greater success in your inquiry investigations on catalase.

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