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Investigating the influence of pH on catalase

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James Fung 3rdDecember, 2001 Biology investigation - Investigating the influence of pH on catalase Introduction: I am going to investigate the effect of reaction rate and the influence of pH on catalast found in potatoes. Background information: Hydrocarbon peroxide is a toxic substance formed during aerobic respiration. It is removed by the enzyme, catalase which is found in many plants and animal tissue. Catalase catalyses the breakdown of hydrogen peroxide into water and the gas oxygen 2H2O2 (l) 2H2O (l) + O2 (g) Equipment and substances needed: 1) Potato 2) Cork borer 3) Scalpel 4) Ruler 5) Ceramic tile 6) Measuring cylinders 7) Stopwatch 8) Gas syringe 9) Conical flask with a lid 10) Citric-acid phosphate buffers (pH3, pH4, pH5, pH6, pH7, pH8) 11) 20 volume of hydrogen peroxide 12) Clamp stands Method and steps: 1) Link a conical flask with a gas syringe and use the clamp stand to hold the gas syringe 2) Cut 20 pieces of potato of 5 mm to 5 mm in size by using the cork borer, scalpel and a ruler on a ceramic tile 3) Measure 10 ml of pH3 buffer and pour it into the conical flask prepared 4) Add those potato cut into the conical flask 5) Measure 10 ml of 20 volume hydrogen peroxide 6) ...read more.


2.25 cm3 / min at pH3. And then as the pH increases, the rate of reaction increases vigorously. But it decreases slightly at pH 8 after it reaches it maximum of 10.25 cm3 / min at pH7. Conclusion: From the basic AS Biology knowledge, for every enzyme there is an optimum pH at which the reaction it catalyses most rapidly. Many enzymes work within a pH range of 5 - 9 and catalyse reactions most efficiently at pH7. There are exceptions. For example, stomach work best at pH1.5 - 2.5. Alkaline phosphatase in the kidneys has an optimum pH of 10. The symbol pH refers to the concentration of hydrogen ions in a solution. The concentration of hydrogen ions [H+] affects the stability of the electrovalent bonds, which help to maintain the tertiary structure of protein molecules. A small change in pH means relatively large changes in [H+]. E.g. a change of 1 on the pH scale involves a ten-fold increase or decrease in [H+] while a change in pH of 2 represents a hundred-fold change in [H+]. Thus even small changes in pH can have a great effect on enzyme activity. There are few effects on the enzyme due to the change in pH. Proteins are denatured by changes in pH because the change in pH affects the ionisation of amino acids. ...read more.


Luckily, there weren't any anomalous results. But if I had a chance to do this experiment again I would reduce all the possible errors and limitations I faced this time as many as possible. In order to do this, I will have to keep those variables, which I mentioned before like: 1) Enzyme concentration --- by using potato from the same pack to make sure consistency 2) Substrate concentration --- by using exactly 10 ml of 20 volume of hydrogen peroxide each time 3) Temperature --- because when I finished the experiment in two different day, although I was doing it in the same laboratory, there might still have a slight difference in temperature which could have affected the result I obtained. So to make sure this kind of things will not happen again, I will have to do the whole experiment in a row within the shortest time in the same day without rushing to get the most accurate result 4) Size and surface area of the enzyme --- by making sure that 20 small pieces of potato are cut each time with 5mm ? 5mm 5) Time for the reaction --- by keeping the time for reaction the same 6) Besides I may use a different buffers e.g. a buffer with pH6 - 14 to see if it will show a different result. The end! ...read more.

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