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Investigation On The Enzyme Trypsin

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Introduction

Investigation On The Enzyme Trypsin Investigation on the Enzyme Trypsin An Investigation determining a factor affecting the rate of digestion of gelatin by the protease trypsin. Introduction An enzyme is a biological catalyst, which speeds up reactions. An example of this in the human body is trypsin (a protease produced in the pancreas and used in the stomach), which catalyses the digestion of gelatine, a protein. For this investigation, a photographic film will be the source of the gelatine. I will be able to identify when the gelatine is digested, when the photographic film turns from a dark brown colour, to being transparent. All enzymes are proteins, which are specific to the molecule that they break down. This is known as the 'lock and key' theory, where the active site only allows a specific substrate to be broken down, eventually resulting in easier absorption (larger surface area). Enzymes are made up of a long chain of amino acids, which form together in such a way as to leave a specific pocket, into which a substrate (as long as it fits perfectly into the pocket) can fit into it like a key in a lock (hence the 'lock and key' theory). The reaction then takes place, and the product of the substrate is then released. The enzyme, not changed by the reaction, can then perform the same "operation" on countless other substrates. Because the enzyme can be re-used, only a small amount is needed. Despite this enzymes can make cell reactions go many million times faster than they would normally. Since enzymes are biological catalysts, by definition, they are not used up or changed in the reaction that they catalyse. Even though they cannot be used up, when subjected to a high temperature (50�C and above), enzymes can become denatured and the active site damaged or destroyed. After denaturisation, the enzyme becomes useless as no more substrates can become further digested by them. ...read more.

Middle

Throughout my investigation, all that I changed was the incubation time of the trypsin, and I made sure that the other independent variables did not alter. This was in order to make the investigation as fair as possible, and so my results could be as accurate as possible. A 50�C water bath was prepared to the nearest �C, and I checked with my thermometer that the water was indeed at 50�C. I then prepared my gelatine, by sliding the photographic film inside the end of the wooden splints. This was done so I could easily operate the gelatine source, and it was much easier to control when it was on the end of a wooden splint. Then I used the syringe to fill a test tube with 2cm3 of trypsin. This was a convenient level, as half of the photographic film would fit inside the trypsin, and I could easily tell when the gelatine had been digested, by comparing the film that had been in contact with the trypsin, and the other half of film, which had not. Once the test tube was prepared, I placed it in the 50�C water bath, and I started the stopwatch. I left it in there (on its own - with no photographic film) for however long I wanted to, and when that time had been reached, I placed the splint containing the film into the test tube. At this point I restarted the stopwatch, and I checked the gelatine for any signs of digestion every 10 seconds. When I realised the photographic film would soon go transparent, I kept a closer eye on the film, and checked every couple of seconds. This way, I was able to record my results pretty much accurately to one second. I noted down the result, and repeated the exact same experiment (with the same incubation time) 5 times. After taking 6 recordings for that incubation time, I then repeated the experiment but increased the incubation time by 1 minute, up until I had obtained results for an incubation time of 20 minutes. ...read more.

Conclusion

My table shows significant variation in percentage decrease, and I think that this was mainly due to timing difficulties. There was also the problem that when I took the splint out to check on the film, for that short period of time the film was not in contact with the trypsin, although the stopwatch was not stopped. Since I had to take each splint out several times to check on the progress of the denaturisation, this built up and would have resulted in at least a few seconds of inaccuracy for each reading. For this reason, if I were to perform the experiment again, I would have asked a classmate to help me when placing the splints in the trypsin. I would ask them to start the stopwatch at exactly the same time as I placed the splint in the trypsin. Also, I would have done 2 experiments at a time. One of them I would check frequently and the other I would leave untouched. When I saw that the one I was checking on had almost gone clear, I would then check the other one and stop the stopwatch when that one had gone clear. I would do this to reduce the amount of time that the gelatin spent outside the trypsin, and I would ignore the result of the other experiment. This, I feel, would improve the accuracy of my experiment, and would probably supply more constant results. In order to extend my investigation, I would investigate the denaturisation of trypsin at 60�C, and see if expediential decay still occurred. I would first wait until the temperature had reached 60�C (this would take a few minutes), and then start timing, because before the trypsin reaches 60�C, the results produced cannot be formed into a conclusion analysing trypsin at 60�C, as the trypsin would never have reached 60�C. (This also leads into the problem that waiting a few minutes for the trypsin to warm up would result in some of the trypsin becoming denatured before timing had started). ...read more.

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