Theeffect of varying pH levels on the enzymatic activityof potatoes
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Introduction, Observations and Hypothesis (Question 2)
Enzymatic activity can be controlled by pH, or what is also know as hydrogen ion concentration. Hydrogen ion concentration can influence the shape of an enzyme, and thus its functionality. There are a variety of enzymes, and each one has a specific pH where it functions most optimally. In this experiment, I investigate the most functional pH range for catechol oxidase, which is an enzyme pound in pieces of potato. I hypothesize that the enzymatic reactions will occur fastest at pH7, which is neutral and at basic pHs (8-14) as compared to the more acidic solutions, which are pH 6 and lower.
Design and Experiment (Question 3)
The materials for this lab are:
21 small tubes or cups
24 ml of potato extract
12 ml each of buffer solutions at pH 2,3,6,8, 10 and 12
12 ml of water
21ml of 1% Catechol
(I borrowed buffer solutions and Catechol from a local university where my Uncleis employed.)
Methods: Step 1 of my experiment was to label my test tubes in numeric order from 1 to 7, with each number also having an a, b, or c, to have 3 replicates per test tube mixture type. In each of these tests tubes I placedabout 1ml with of potato extract. After this, tube #1a-c, I added 4ml of pH2 solution and in test tube #2a-c, I added 4 ml of pH4 solution.In test tube #3a-c, Iadded 4ml of pH6 solution. I also added 4ml of pH8 solution to test tube #4a-c, and 4ml of pH10 solution in test tube #5a-c. In test tube #6a-c, I added 4ml of pH12 solution, and in test tube #7a-c, I added 4ml of water, which is pH7. As the final step, I added 1ml of 1% catechol to each solution.
I decided to use a color intensity scale of 1-5 to record if the reaction occurred. The darker and more drastic the color change (as score close to 5), the quicker the reaction was taking place. At the beginning of my experiment I recorded their initial colors at time 0 minutes. Then I placedall the test tubes in a warm water bath about 40degrees C. After waiting 15 minutes, Iobserved and recorded the color for a final time.
Conduct the Experiment and Record the Results (Question 4)
Data Collection
I observed that the most acidic solutions had the lowest scores, and the most basic solutions had intermediate scores. Lastly, I observed that the more neutral solution had the highest scores.
Tube # / Potato Extract / pH of Buffer 4ml / 1% catechol / Time 0min(Same for A-C, for all) / Time 10min / Average Color Intensity Score
1a-c / 1ml / 2 / 1ml / Clear with a faint blue tint / Faint blue tint for A and B, Medium blue for C / 0.5
2a-c / 1ml / 4 / 1ml / Clear with a faint blue tint / Light blue tint for A-C / 2.5
3a-c / 1ml / 6 / 1ml / Clear with a faint blue tint / Light blue for A and C, Medium for B / 3
4a-c / 1ml / 8 / 1ml / Clear with a faint blue tint / Blue for A and C, Medium to dark for B / 4
5a-c / 1ml / 10 / 1ml / Clear with a faint blue tint / Light blue for A-C / 3.5
6a-c / 1ml / 12 / 1ml / Clear with a faint blue tint / Light blue tint for A-C / 2
7-ac / 1ml / Water (7) / 1ml / Clear with a faint blue tint / Most blue for A-C / 5
Discussion and Conclusion (Questions 5 and 6)
From this experiment, I learned that acidity plays a big part in the functionality of enzyme activity. I determined that the reaction times were fastest for those that were exposed just to water solutions or those that were basic. From my dataset, I also realized that the more acidic the solution, the slower the reaction. It could be that the acid was decreasing the functionality of the enzyme. I originally hypothesized that the enzymatic reactions will occur fastest at pH7 as compared to the more acidic solutions, where darker colors indicate faster enzymatic activity. My data support my hypothesis. To improve this experiment, I could have conducted replicates per tube type to insure the accuracy of my results.
References (Question 7)
Introduction to Enzymes. (2014, January 1). Dec 5, 2015, from
Kinetics: Determination of an Enzymes Activity - Relevance. (n.d.). Retrieved Dec 4, 2015, from
Reece, J. (2008). Biology (Second custom ed.). Boston: Pearson Learning Solutions.