Objective

To determine the effect of temperature on catalase activity

Background

Catalase is an enzyme that breaks down toxic hydrogen peroxide in living cells, converting it to water and oxygen. Since catalase is a protein, its activity is affected by various conditions that could lead to full or partial denaturation, for example, change in pH, salt concentration, and temperature. In this lab we will be examining how catalase is affected by temperature.

Materials and Equipment

  1. Vernier LabQuest
  2. Vernier oxygen sensor
  3. Hydrogen peroxide (3%)
  4. Potato pieces (Treatments = (1) freezing, (2) boiling, and (3) room temperature)
  5. Digital scale

Method

  1. Prior to the start of the lab, one medium sized potato will be diced into approximately 1/4-inch pieces and divided into 3 parts. One third will be boiled for 3 minutes and then stored in the refrigerator; one-third will be frozen overnight; and one-third will be placed in the refrigerator without any additional treatment
  2. About two hours before the lab starts, remove the two sets of refrigerated potato and set them on the lab counter to adjust to room temperature. Let the third that was frozen remain in the freezer until you are ready for the experiment
  3. Set up the Vernier LabQuest and oxygen sensor as shown in the diagram below
  4. Add 50 ml of 3% hydrogen peroxide to the oxygen sensor bottle
  5. Set the oxygen level to zero on the LabQuest
  6. Set the run on the LabQuest for 300 seconds and the unit as ppm
  7. Collect approximately 10 grams of the food treatment assigned to your group
  8. Add the sample to the oxygen gas sensor bottle, attach the sensor, and press the green start button on the LabQuest
  9. The sensor will start measuring the amount of oxygen produced for the next 300 seconds
  10. After 300 seconds, measuring will stop. At this point, go to the data table on the LabQuest and record the total oxygen released at each 60 second interval

Vernier LabQuest and oxygen sensor

Data Table

Lab Questions (12 points)

  1. Plot the three line-graphs (for boiled, frozen, and raw) on the same chart showing oxygen concentration (ppm) on the y axis and time (seconds) on the x axis (5 points)
  2. What was the dependent variable in this experiment? (1 point)
  3. What was the independent variable in this experiment? (1 point)
  4. Write a conclusion statement base on the graph that was obtained (5 points)

Data Collected

As expected, the boiled potato showed no activity due to complete denaturation of catalase during cooking. The raw sample had a lower activity than the frozen sample. This was no expected since the optimum temperature (37oC) of catalase was closer to the temperature at which the raw potatoes were stored before the experiment. Potential errors may include differences in size of the potato pieces and hence differences in surface area. Partial thawing of frozen potatoes before running the test may have also played a role.

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Courtney Simons
Courtney Simons
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Courtney Simons is a food science professor. He holds a BS degree in food science and a Ph.D. in cereal science from North Dakota State University.