The Effect of low pH on Enzyme Activity

2. Introduction: general background information about enzymes and specific information about your chosen enzyme, the question(s) that you are asking and a clear hypothesis for your experiment (20 points).

3. Provide a detailed description of the materials and methods used to conduct the experiment. (expeirment and results are below) Identify control and experimental samples, as well as independent and dependent variables. Also include the methods used for data collection and analysis (20 points).

5. Use your knowledge of enzymes and pH to interpret and discuss your results. It may be necessary for you to refer to the OLI course modules, lab manual and/or use additional information resources. What effect does the acidic treatment have on enzyme activity? Did you get the expected results? Explain. (20 points)

6. State a specific and accurate conclusion. Is your hypothesis supported by the results? Looking back, how could you have improved your experiment? (10 points)

7. Include a list of references to all information sources used in APA format (5 points).

Experiment & results

The effect of vinegar on catalase’s yeast activity.

Hypothesis. The enzymatic activity of the catalase’s yeast will be reduced by the addition of vinegar. The more vinegar that we add, the pH level will we be reduced and the activity will be lower.

Materials and reagents: pH paper, hydrogen peroxide solution (3%), plastic beakers or cups, (250mL or more) vinegar (acetic acid 5%), sugar, yeast, marker for labeling of beakers, tweezers, scissors, two spoons (for 1 tablespoon and ½ tablespoon measure) cylinder, chronometer, paper towel, filter paper, mortar and pestle.


  • Elaboration of the vinegar solutions
  • Preparation of the filter paper disks: Draw circles that could fit in a plastic beaker or cup. The idea is that you can put it easily on the bottom using the tweezers.
  • Elaboration of the vinegar-yeast solutions:
    • In a mortar, add 1 tablespoon of yeast and begin to mix the components, using the pestle, and begin to add the vinegar solution (being with the 0% concentration) until you have a paste. Transfer all the contents to the cup where is the remaining vinegar solution that you use. (For example, if you are working with the 0% solution, the paste will be poured in the beaker labeled as 0%)
    • Repeat step 3a with every solution of vinegar, from the least concentrated to the highest concentration (100%).
  • Trials.
    • In a clean beaker, add some hydrogen peroxide solution and ½ tablespoon of sugar.
    • Use a filter paper disk and use the tweezers to soak it into a vinegar-yeast solution for 30s. (Remember to mix again the solution to ensure homogeneity)
    • Using the tweezers, put the filter paper disk on a paper towel sheet to take the excess of the solution.
    • Using the tweezers, introduce the filter paper into the bottom of the hydrogen peroxide solution and start the chronometer when you release the filter paper.
    • Take the time that takes to the filter paper goes from the bottom to the top of the solution.
    • Repeat steps 4b to 4e for every vinegar-yeast solution. Record the time for every trial.

In different plastic beakers or cups, prepare 200mL of vinegar solution using the following proportions detailed in the table. (Don’t forget to label the beakers as 0%, 1%, 5%, 10%, 50%, 100%)

Vinegar (mL)

Water (mL)

Concentration (%)



















Results of experiment

0 – 5.58 seconds

1% – 13.50 seconds

5% – 14.15 seconds

10% – 20.75 seconds

50% – 1m05s20 seconds

100% – 20 minutes later filter paper still stayed submerged in the solution

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