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Investigating the Factors That Affect the Activity of Trypsin

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Investigating the Factors That Affect the Activity of Trypsin Planning Aim: To investigate how pH affects the activity of trypsin. Background Knowledge An enzyme is composed of polymers of amino acids that act as catalysts within living organisms. They speed up chemical reactions within the body, without which these reactions would occur too slowly, causing the organism to die. They are not themselves used up in this process. They break down large nutrient molecules within the body into smaller ones. The way they do this is by the lock and key theory. That is, each enzyme has its own shape that fits like a lock fits with a key with the appropriate substrate. It is the sequence of amino acids that make up an enzyme that determine the 3D shape of an enzyme and hence its specificity. Its unique shape prevents the enzyme reacting with the wrong substrate. An enzyme is a lot bigger than its substrate, so only a small portion, which comes into contact with the substrate, is active. Enzymes usually (but not always) work best at neutral pH. While heat does speed up a reaction, it can also change the shape of an enzyme (as can pH) making it useless. The graphs show the effect of pH and temperature on an enzyme-controlled reaction. ...read more.


Another factor which may affect the accuracy of our results, is we may not know exactly when the reaction has taken place. Not only are 6 samples difficult to keep watch over, you can't always tell if the reaction has taken place as there may still be loose particles which have not come free of the film. Another point to consider, is with the stirring. It is inevitable that one will get more vigorous stirring than another, it is impossible for humans to regulate their stirring exactly. This will cause loose particles of silver to come off, clearing the film sooner than otherwise, giving the false impression that the reaction took place faster than it actually did. Prediction From the knowledge I have obtained, I think that the reaction will be fastest at pH 8, as this is trypsin's optimum pH. Those pHs closer to 8 will also react reasonably quickly but not as fast as 8, and the more acid or alkaline the buffer solution, the slower the reaction will be. This will be due to a deficiency/excess of H+ ions which will affect the enzyme's performance. Looking at my preliminary results, the film took 419 seconds to go clear at 5% concentration under pH 9. Because this is slightly more alkaline (less H+ ions) ...read more.


Some were given longer than others and it is possible that perhaps pH 8 was not given long enough to equibriate in the first instance. Some pieces of photo film were also bigger than others, as it was difficult to measure them exactly and to cut them, holding them with the tweezers as we could not allow our skin to come into contact with the film. Another limitation was the stirring of the buffer solution. We tried to stir them all equally vigorously, however this was not always possible and some were shaken more vigorously than others, shaking some silver particles loose from the film, giving the false impression that the reaction took place faster than it actually did. It is only by averaging the two results for pH 8 and 9 that we get the impression that 8 is the optimum. Although we know, from the background knowledge that it is 8, further investigation would be required in order to test this theory. Perhaps by investigating how the enzyme reacts under pH 8.5. Another thing would be to test each pH individually, as it was difficult to test them all simultaneously with one stopclock, as it was hard to tell exactly when all the gelatine had been digested. Ideally, we would have also liked to test each pH a third time, for greater accuracy. But overall, I think there is sufficient evidence to support a firm conclusion. ...read more.

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