Each enzyme works best at a particular pH, called its optimum pH.
Apparatus
The apparatus for this investigation is almost exactly the same as that used for the investigation into the effect of temperature on catalase, but with a few exceptions. Rather than having two water baths at different temperatures, and a beaker full of icy water, five beakers all containing solutions with different pHs are needed. Beakers with pH 2, 4, 6, 8, and 10 were used. 5 test tubes are also required, one for each pH as there are no repetitions. Also, the thermometer is obviously not required. Other than that the apparatus was the same.
Method
Again the method for this is almost identical to the method for the temperature investigation, with just the variable changed. 5 samples of potato tissue were taken with the cork borer, and then these were measured to 1.5cm each. 5 test tubes were labelled –one for each of the pH solutions used – 2, 4, 6, 8 and 10. The potato tissue samples were then placed in the test tubes, with 5cm³ of hydrogen peroxide 10 drops of detergent. The pH solutions were then added to their respective test tubes. The test tubes were then left in the test tube rack for five minutes while the enzymes reacted. After five minutes the level of froth at the top of the test tubes was measured using the ruler and then recorded.
Results
Conclusion
From our results, we can conclude that the optimum pH for catalase to function is a high, and more alkaline pH. In our investigation the best solutions for enzyme activity were pH8 and pH10, both very alkaline solutions. Enzymes function better under high pH solutions. This is because the shape of an enzyme is party due to hydrogen atoms which hold its chains of amino acids together. If an enzyme is exposed to extreme pH solutions, like the high concentration of hydrogen ions in a strong acid solution, these chains are broken and the enzyme becomes denatured and cannot function.
Evaluation
As this experiment was so similar to the previous investigation, the possible sources of error were generally the same. Once again there was the possible error in the timing – the enzymes may have been given to much or too little time to react. More careful and accurate timing would have reduced the possibility of an error which could have affected the results. Any error that occurred would have completely skewed our results, because there weren’t even any repetitions of this experiment. Each pH was used only once, and this could have made our results invalid. More repetitions were definitely needed to make this experiment valid, because a single freak results would have altered our whole conclusion. There was also the possibility of the wrong volume of hydrogen peroxide, detergent, or the pH solution being added to the tissue, so perhaps more careful measuring is needed. Our range of pH solutions was fairly wide so that does not really need to be improved, but since our results showed that pH8 and pH10 were the optimum pH levels for catalase activity, another test tube with pH9 used would have helped us to discover if that was the optimal pH. This would have made our results more accurate and we could perhaps have found the single best pH for catalase activity.