10.2: Exercise
Part 1: Observe the Effects of Catalase
Procedure
- Obtain two test tubes and label one as A and one as B.
- Use your ruler to measure and mark on each test tube 1 cm from the bottom.
- Fill each of two test tubes with catalase (from the potato) to the 1 cm mark
- Add 10 drops of hydrogen peroxide to the tube marked A.
- Add 10 drops of distilled water to the tube marked B.
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Wait 60 seconds and measure the height of any bubbling you observe.
- Bubbling height tube A
- Bubbling height tube B
- What happened when H 2 O 2 was added to the potato in test tube A?
- What caused this to happen?
- What happened in test tube B?
- What was the purpose of the water in tube B?
Part 2: Effects of pH, Temperature, and Substrate Concentration
Observations
From the introduction and your reading, you have some background knowledge on enzyme structure and function. You also just observed the effects of catalase on the reaction in which hydrogen peroxide breaks down into water and oxygen.
Questions
From the objectives of this lab, our questions are as follows:
- How does temperature affect the ability of enzymes to catalyze chemical reactions?
- How does pH affect the ability of enzymes to catalyze chemical reactions?
- What is the effect of substrate concentration on the rate of enzyme catalyzed reactions?
Hypotheses
Based on the questions above, come up with some possible hypotheses. These should be general, not specific, statements that are possible answers to your questions.
- Temperature hypothesis
- pH hypothesis
- Substrate concentration hypothesis
Test Your Hypotheses
Based on your hypotheses, design a set of experiments to test your hypotheses. Use your original experiment to shape your ideas. You have the following materials available:
- Test tubes
- Catalase (from potato)
- Hydrogen peroxide
- Distilled water
- Hot plate (for boiling water)
- Ice
- Acidic pH solution
- Basic pH solution
- Thermometer
- Ruler and wax pencil
Write your procedure to test each hypothesis. You should have three procedures, one for each hypothesis. Make sure your instructor checks your procedures before you continue.
- Procedure 1: Temperature
- Procedure 2: pH
- Procedure 3: Concentration
Results
Record your results—you may want to draw tables. Also record any observations you make. Interpret your results to draw conclusions.
- Do your results match your hypothesis for each experiment?
- Do the results reject or fail to reject your hypothesis and why?
- What might explain your results? If your results are different from your hypothesis, why might they differ? If the results matched your predictions, hypothesize some mechanisms behind what you have observed.
Communicating Your Findings
Scientists generally communicate their research findings in written reports. Save the things that you have done above. You will be use them to write a lab report a little later in the course.