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'The effect of changing the concentration of the substrate hydrogen peroxide on the rate of activity of the enzyme catalase.'

Extracts from this document...

Introduction

'The effect of changing the concentration of the substrate hydrogen peroxide on the rate of activity of the enzyme catalase.' Catalase occurs very widely in cells of living things. Catalase is a protective mechanism for the delicate biochemical machinery of cells. Hydrogen peroxide is a common by-product of the reactions of metabolism. Hydrogen peroxide is a highly toxic substance and is a very powerful oxidising agent. Catalase catalyses the breakdown of hydrogen peroxide to water and oxygen. Catalase breaks down hydrogen peroxide as soon as it forms before it can damage the cell. This is a good example of an enzyme-controlled reaction. This reaction is known as a catabolic reaction because a molecule is broken down into smaller pieces. Enzymes are biological catalysts, which control biological processes but remain chemically unchanged themselves. Enzymes act on specific substrates; catalase is specific to hydrogen peroxide. Hydrogen peroxide Catalase Water Oxygen 2H2O2 2H2O O2 To investigate the effect of changing the concentration of the substrate hydrogen peroxide on the rate of activity of the enzyme catalase, I am going to measure the amount of oxygen produced. I am going to use potato cylinders to explore this because catalase occurs in potato cells. In the experiment there are several variables that could affect what happens, these are: o Size, shape and surface area of the potato cylinder o Volume of hydrogen peroxide and distilled water o Concentration of hydrogen peroxide o Temperature of hydrogen peroxide o pH of hydrogen peroxide o Variety of potato used o Mass of potato cylinder o How the potato is handled o Amount of time potato cylinders left in solution Size, shape and surface area of the potato cylinder The size, shape and surface area of the potato cylinder can affect the rate of activity because the greater the size, the faster the rate of activity because there are more cells with the enzyme catalase. ...read more.

Middle

In addition I predict that if the solution has 0% of the original solution of hydrogen peroxide I predict that no oxygen will be produced because there is no hydrogen peroxide to be broken down. I first tried the 100% of original solution of hydrogen peroxide. The potato cylinder I used weighed 1.07g and measured 2.0cm in length. I checked the amount of oxygen produced after every minute for ten minutes. Below is a table with my results. Time (minutes) Amount of oxygen produced (cm3) 1 1.2 2 1.7 3 2.2 4 2.6 5 3 6 3.5 7 3.9 8 4.3 9 4.6 10 4.9 I then tried the 20% of original solution of hydrogen peroxide. The potato cylinder I used weighed 1.06g and measured 2.0cm in length. I checked the amount of oxygen produced after every minute for eight minutes. Below is a table with my results. Time (minutes) Amount of oxygen produced (cm3) 1 0.7 2 1 3 1.1 4 1.3 5 1.5 6 1.7 7 1.9 8 2 Below is a diagram of how I am going to set up my equipment: I have set out the equipment like this so there are no loops in the delivery tube and also I can see both the gas syringe and the test tube. On the diagram above I have not drawn several parts, I have not drawn the clamp that will attach the syringe to the stand, nor I have I drawn the test tube holder that will hold the test tube in place. I did not draw these because in this drawing they will obstruct the view of the syringe and test tube. To carry out the investigation I will first wash my equipment with distilled water, to make sure they are clean. Then I will cut the bottom of the potato off, with a knife so I have a flat surface to work with, this way the potato can't slip and I can't hurt anyone. ...read more.

Conclusion

This would have slightly affected the results, but as the procedure was repeated on each occasion, the error will be the same throughout the experiment. Another error occurred when readings were taken, these were taken by eye, and although they were taken by looking at the scale as near to right angles as possible, there may well have been possible errors. Errors could also have occurred when trying to get all the tissue the same size and the same mass, this would have come through problems with cutting tissues to the same length and also cutting the tissue at right angles each time. Some cylinders may have been cut at a slope and therefore they have increased in surface area. I did not monitor any changes in the temperature of the hydrogen peroxide and this may have altered my results slightly, this was very had to control because we had a rubber bung in the end of the test tube, so there was no where for a thermometer to go. I could have controlled the temperature of the hydrogen peroxide better by putting it in a water bath, to try and keep the temperature more constant. The procedure of this experiment could be improved, although the results do give adequate conclusions. Improvements would simply remove certain errors, and improve the accuracy of results. Using slightly different procedures could reduce the delay between putting in the hydrogen peroxide and replacing the bung and starting the stopwatch. The best solution would be to find a method that doesn't require the bung to be removed and replaced each time. The study of the enzyme catalase could be further investigated by analysing the effects of temperature upon the rate of the reaction between the enzyme and hydrogen peroxide. Although catalase can withstand reasonably high temperatures, it would probably denature at extreme temperatures. It would be interesting to investigate at what temperature catalase stops working. Biology Coursework Charlotte Nellist Page 1 ...read more.

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