To find out the optimum pH at which the enzyme catalase would best break down hydrogen peroxide.

Essay by kwjsrhaeHigh School, 11th gradeA+, May 2005

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PLANNING: Skill Area P

Write down the aim of your Investigation.

The aim of investigation is that to find out the optimum pH at which the enzyme catalase would best break down hydrogen peroxide.

Briefly describe your Preliminary Experiment and include your results. Explain how these results have helped you plan your main experiment (p8b).

The purpose of the preliminary experiment was to find out the best source of catalase for the investigation. The four choices of sources which were available were liver, apple, yeast and potato. Each source was cut up into 1cm3 sections and placed in four separate test tubes which each contained 5ml of H2O2. Observations were made on the physical evidence of what happened.

Catalase source Degree of bubbling Number of times

relights glowing splint

potato normal 1

apple little 0

liver a lot 7

yeast Quite a lot 3

As the result show above, the potato was considered to be the best source to be used in the real experiment because it produced enough oxygen (but not too much to cause a dangerous situation).

The apple did not appear to have sufficient catalase for the experiment as it did not produce any oxygen. The yeast and the liver, while rich in catalase unfortunately proved to be over sufficient with an unnecessarily large supply of the enzyme needed. The oxygen is produced by this equation:

List all the apparatus that you now plan to use (diagrams should be included) (P4b).

20ml of each buffer solution from pH3 to pH8

120ml of H2O2 6 test tubes

Three medium sized raw potatoes one cork borer

50ml Manometer fluid 2x syringes

1x Ruler 2x Pipettes

1x White tile 1x stopwatch

1x scalpel 2x measuring cylinder

1x clamp stand 1x glass pencil

Describe the method...