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The aim of this experiment is to demonstrate the effects of pH on potato catalase. My substrate is hydrogen peroxide and the enzyme catalase will be from three types of potatoes.

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Aim The aim of this experiment is to demonstrate the effects of pH on potato catalase. My substrate is hydrogen peroxide and the enzyme catalase will be from three types of potatoes. INTRODUCTION Enzymes are an important part of all living organisms in that they regulate chemical reactions within the organism. Enzymes are biological catalyst made of globular protein that speed up a reaction by lowering the activation energy while at the same time they do not take part of it. Because of enzyme's tertiary arrangement they are specific in the job they do and they can be altered by high temperatures, high pH and also by irreversible inhibitors. Enzyme denaturation is a result of the breaking of the hydrogen bonding, ionic bonding and/or the disulphide bonding which hold the enzyme molecule in its three dimensional shape. The shape that is altered is the active site which fits into a specific substrate. This is why the enzyme mechanism is known as the Lock and Key mechanism. The way a key is design to open a particular door so too is the design of the enzyme. The substrate fits into the active site to form an enzyme substrate complex. A product is then released. The enzyme catalase is an enzyme that is present in the cells of plants, animals and aerobic (oxygen requiring) ...read more.


Cube Size (cm3) Length of Potato (cm) Time taken in minutes Oxygen Produced 1 2 1 6 5 4.0 2 3 1 6 5 6.0 3 4 1 6 5 9.0 4 5 1 6 5 11.0 5 8 1 6 5 21.0 Here the results show see that the best volume of hydrogen peroxide was 8ml because it releases the largest volume of oxygen. Pilot 3 The third and last pilot test that was done was that of the volume of pH solutions that required for the main experiment. The volume of hydrogen peroxide obtained from pilot 2 was used and kept constant. The size of the potato was also kept constant. Test Number Volume of pH (ml) Cube Size (cm3 ) length of potato (cm) Time Taken in minutes Oxygen Produced (ml) 1 2 1 6 5 19.0l 2 3 1 6 5 17.0 3 4 1 6 5 25.0 4 5 1 6 5 21.0 4ml of pH was the best volume because it produced the most oxygen Apparatus need Water basin Test tubes Test tube bungs Delivery tubes Measuring cylinder Syringes 10ml and 5ml Digital stopwatch Beakers 50ml Beehive Gas syringe pH solutions pH (pH2-pH4 -pH 6 -pH 7 -pH 9) Hydrogen peroxide 20 volumes Three types of potatoes Desiree, Maries Piper and Estima Cutter and ruler Health and safety rules When working in the lab one must always be extremely careful. ...read more.


basic) solutions there is lots of hydroxyl ion free in this solution. This too also changes the active site of the enzyme making it produce less products and eventually resulting in denaturation of the enzyme if the pH is increased even more. There is an anomalous. The Maries Piper potato gives an odd result in that pH2 has a higher oxygen gas production then pH4. The values are also fairly low compared to that of the other two potatoes. This could be a result of the soil in which it was grown. When soil becomes acidic alkalis such as calcium hydroxide or calcium carbonate are used to neutralise the soil. If excess alkali is deposited into the soil it becomes basic and the vegetation could be contaminated with it. Evaluation: - The experiment is fairly accurate. The only method that contributes to in accuracy is the pressure at which the hydrogen peroxide is injected into the test tube. This is because during the course of the experiment the ones hand gets tired and sore therefore stops when injecting the contents into the test tube. The is not completely accurate at 5 minutes. There were always a few seconds that went with it. If the seconds seemed close to another minute the experiment was repeated to be as accurate as possible. During the course of the experiment the hydrogen peroxide might have been decomposed by light energy. The best thing to have done is to have kept it in a black container. ...read more.

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