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An Investigation into the effect of surface area on the activity of catalase in potato

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Introduction

An Investigation into the effect of surface area on the activity of catalase in potato In this investigation I will be adding pieces of potato (with different surface areas) to hydrogen peroxide. A reaction will take place because fizzing will occur. My aim is to investigate the amount of fizzing to the surface area of the potato. Potato contains catalase, which is an enzyme, found in all aerobic tissues. Its job is to catalyse the breakdown of hydrogen peroxide into water and molecular oxygen. It's important hydrogen peroxide is removed from cells because it becomes poisonous. Enzymes are biological catalysts so they will speed up a reaction. They work as follows: I predict that when the surface area of the potato piece is increased by a constant, the rate of reaction will also increase by that constant so the surface area of the enzyme will be directly proportional to the rate of reaction. E.g. when the surface area is doubled then the rate of reaction will double. This is because when the surface area of the potato is doubled, double the amount of enzymes (active sites) are made available to the hydrogen peroxide, so there's double the chance of collisions between the active sites and the hydrogen peroxide. To prove my prediction I will calculate the surface areas of each potato piece(s) from each experiment. This will allow me to calculate how much the surface area has been increased (see appendix 1). I will then calculate the gradient of each reaction (after the results have been plotted on a graph). ...read more.

Middle

This is because the enzyme molecules are becoming denatured. This means the enzymes have too much energy so they start to breakdown bonds on active sites that give it stability and shape. The shape of the active site is then changed and the hydrogen molecules would no longer fit and a reaction would not take place. To maintain a constant temperature I will ensure there is little or no contact between my hands and the potato/hydrogen peroxide. I can do this by using tongs. All the experiments will be conducted at room temperature. * pH Like temperature, enzymes also have an optimum pH. At this optimum pH the enzymes work best and variations either side of the pH scale denature the enzyme causing it to work less effectively. To ensure a fair test all experiment will be conducted using the same pH of hydrogen peroxide. * Concentration of Hydrogen Peroxide A change in the concentration may have an affect on the rate of reaction. If there isn't sufficient hydrogen peroxide to fill all the active sites then an increase in concentration will increase the rate of reaction because there will be more hydrogen peroxide molecules to fill the active sites. A lower concentration will decrease the rate of reaction. To maintain a fair test the same concentration of substrate (20%) will be used. The same volume of hydrogen peroxide will also be used. * Inhibitors In this experiment, Inhibitors would compete with the hydrogen peroxide for the active site of the enzyme. ...read more.

Conclusion

This allowed some gas to escape. There was also a delay between the start of the reaction and the starting of the stopwatch. This reduces the accuracy of the results. I believe these factors would significantly affect the accuracy of my experiment. It's also impossible to measure out accurately the hydrogen peroxide because the syringe measures to the nearest mm� however I don't think this significantly affected the reliability of the results. Another reason for the anomalous results is the fact that there was an un even arrangement of cells on the surface of the potato which means some surface would have more enzymes available compared to other pieces. You can tell this because some bits were a slightly darker colour compared to others. I used a lot of the potato so I was comparing pieces from the middle with pieces from the edge. This would affect the experiment because there would be different concentrations of enzymes in the middle and edge of a potato. To improve the experiment a gas syringe could be used however more substrate and more enzymes would need to be used, otherwise the syringe wouldn't move a significant amount to make it affective. A gas syringe would make it easier and quicker to read the amount of gas produced. If another person helped with the experiment then they could be used to start the stopwatch at exactly the correct time, improving the reliability of the results. The experiment could also be repeated more times and a more accurate average could therefore be taken. This is because anomalous results would be cancelled out by the other sets of results. ...read more.

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