Factors Affecting Enzyme Activity

How is pH affecting catalase activity?

Hypothesis
The catalase activity is assumed to be the most active in pH7. The higher or lower concentration away from the optimum pH of catalase, the slower the rate of activity is.

Data Collection & Processing
I collected the results of pH4, pH7, pH10 and pH13 after 2 minutes, and I repeated the experiment 3 times. Below is a table to show the results, their averages and standard deviations: | 1st time (sec) | 2nd time (sec) | 3rd time (sec) | Average(4 d.p.)(sec) | STDEV(6 d.p.) (sec) | pH4 | 21.3927 | 22.6571 | 21.8604 | 21.97007 | 0.639294 | pH7 | 22.6128 | 24.8359 | 23.4023 | 23.74343 | 1.112041 | pH10 | 24.5181 | 23.7816 | 24.8846 | 23.38243 | 1.512198 | pH13 | 19.1448 | 20.3342 | 20.0647 | 19.8479 | 0.623634 |

I used the averages of each pH to make a graph, which I also added the error bars. Below is the graph:

According to the graph, it shows that the rate of catalase activity increases from pH4 (21.97007sec) to pH7 (23.74343sec). The rate of catalase activity of pH7 is almost the same with pH10 (23.38243sec), but pH7 has a slightly higher and faster rate. When it goes to pH13 (19.8479sec), there is a significant decrease.

Conclusion
The results match with my hypothesis, which the catalase activity is assumed to be the most active in pH7. The higher or lower concentration away from the optimum pH of catalase, the slower the rate of activity is. This shows that different pH has affection on the catalase activity, and that catalase will denature in the pH after pH10. At the start of the reaction, there is no product, and the concentration is the same as the atmosphere. After a short time, oxygen accumulates at a rather constant rate. The slope of the curve at this initial time is constant and is called the initial rate. As the peroxide is destroyed, less of it is available to react and the O2 is produced at lower rates. When no more peroxide is left, O2 is no longer produced.

Evaluation
There are quite a lot of errors when I was doing the experiment. After I pour the mixture of pH buffer, H2O2 and pig liver extract into the reagent bottle, the reaction is already starting. However, I still need more time to adjust the screen on the GDC, which I already missed many data. I should have known more about how to operate the GDC before doing the experiment; therefore I can save more time and avoid errors.
Another error was I did not know how long I should let the reaction lasts in order to collect data; therefore I chose to collect the data after 2 minutes. But I never know if there will be any more significant difference or changes more than 2 minutes. For improvements, I would do more research of how long will the reaction lasts, and then I will adjust the time of letting the reaction goes on.
The biggest problem of this experiment was I did not know how to operate the gas sensor. I spent so much time just to figure out how to use it and collecting the wrong data. More research and experiences are needed.
These different errors made the results not reliable and not accurate.

APA Reference

Vernier Software & Technology. Biology with Vernier. Retrieved from http://www2.vernier.com/sample_labs/BWV-06A-COMP-enzyme_action_O2.pdf