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I aim to investigate the enzyme Tripsin, and the factors that affect the rate at which it hydrolyses proteins.

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Biology Coursework Introduction I aim to investigate the enzyme Tripsin, and the factors that affect the rate at which it hydrolyses proteins. Tripsin is an enzyme that acts in the small intestine of mammals. It is secreted by the pancreas, in the pancreatic juice. This suggests some things that may be important when conducting the experiment. Firstly, it suggests that the optimum temperature for Tripsin would be around the body temperature of mammals, i.e. just below forty degrees centigrade, and secondly, it indicates that the optimum pH would be about 8. This is because pancreatic juice contains sodium hydrogencarbonate, so that the acid from the stomach is neutralised. The pH of the environment in which the enzyme is working affects the enzyme in two ways; the hydrogen ions interfere with the attraction between the enzyme and the substrate, so each enzyme has a specific pH at which the concentration of hydrogen ions is just right for the maximum attraction between the molecules. But the pH also can break the twist and misshape the bonds in the enzyme molecule, thereby misshaping the active site, and so denaturing the enzyme. Therefore, the graph of enzyme activity against pH is usually a bell shaped curve. The temperature affects enzymes in a similar way, but with different consequences; the higher the temperature, the faster the molecules move, and therefore, a higher temperature means more collisions between the substrate and enzyme. However, high temperatures can permanently deform the enzyme, so the optimum temperature is the maximum temperature before the enzymes start to be denatured too much. The graph below demonstrates this:1 Rate at which enzyme activity decreases due to denaturation Enzyme Activity Speed of substrate (heat) Temperature This displays the idea that as the temperature increases, the number of collisions between the enzyme and the substrate increases, but so to does the rate at which enzymes are being denatured. ...read more.


4) Then I repeated this process of checking if the film has gone clear every ten seconds until it went transparent. It did not gone clear after six minutes, so I recorded this on the results sheet as more than six minutes. I made sure throughout the experiment that I did exactly the same thing each time I took out the film. 5) I then mixed up more test tubes replacing the pH 3 buffer with pH 4, then 5, 6, 7, 8, 9 and 10, and carried out the experiments with each different pH 6) I found that I could conduct two or more experiments at once, without losing any significant amount of accuracy, and so decided that in the given time it would be better to do the each experiment twice, while doing two or three experiments at once. 7) After one experiment, I noticed that the result was very different to what I expected, and the result I had got in a previous experiment with similar conditions, so I repeated it. When I had completed this set of experiments, and was confident of the accuracy of my results, I still had some time to investigate further into the workings of the enzymes so I decided to explore the effects of ions other than those found in the acid or alkali. Therefore, I decided to test what would happen if I added salt to the solutions, and see if these ions interfered in any way with the enzyme-substrate bonding. I mixed 1cm3 of saturated salt solution with 0.5cm3 of pH8 buffer, and 0.5cm3 of 4% Tripsin solution, so that I had a 1% solution of Tripsin. I also mixed a test tube with 1cm3 of pH8 buffer, and 1cm3 of 2% Tripsin solution, and placed both of these in the 51oC water bath, and carried out the experiment as above, taking car to do exactly the same thing to each test tube. ...read more.


Further Work As I have said above, if I were to repeat the experiment, I would try to improve the overall accuracy. I would do this by using a more accurate method for measuring the solutions, such as with a glass pipette. I would also try to find a way so that I could check on the film more frequently than every ten seconds. If I took it out every five seconds, then I would be faced with the problem that I would have to take the film out of the water up to twenty times, and so might introduce another error. I think that the best way would be to conduct the experiment in a transparent water bath, so that I could continually monitor the film without taking it out of the bath. If glass water baths have not been invented by the time I come to repeat this experiment, I could set up some sort of hi-tech solution, such as an underwater video camera, which would allow me to watch the piece of film in technicolour, as it is slowly hydrolysed away, and so record the exact time at which it goes transparent. This would cut the margin of error from 10 seconds to around 1. I would be interested to investigate the effects of adding salt solution, when the buffer is at different pHs. I would repeat the experiments that got me the results about the effects of salt solution on the rate, but instead of using pH 8 buffer, I would try other pHs. This would give me data about the combined effects of pH and salt solution, and so would help me to understand the effects of salt solution further, especially if I could compare the results of different pHs with and without salt solution. I do not think that all pHs would be affected in the same way. 1 Toole and Toole Understanding Biology 2 Advanced Biology by W R Pickering 3 Toole and Toole - Understanding Biology Hector Guinness 03/05/2007 1 ...read more.

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