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The effect of temperature on the rate of an enzyme catalysed reaction

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Introduction

Biology AS Skills I, A & E The effect of temperature on the rate of an enzyme catalysed reaction By Rebecca Steptoe A Table to show the rates of reaction when an enzyme-catalysed reaction was carried out at different temperatures Temperature/ �C Time taken/Secs (to nr 30s) Time taken/Mins Rate 1 . Time /Min Room (20) 165 5.5 0.2 30 150 2.5 0.4 40 120 2 0.5 50 90 1.5 0.7 60 90 1.5 0.7 70 60 1 1 See Graph: According to the graph the optimum temperature this enzyme, trypsin, works at is 80�C. Meaning As the graph has shown us the optimum temperature for trypsin in this experiment is apparently 80�C, however it is known that this result is not possible since enzymes are denatured at around 40�C. As the temperature rises the enzyme and substrate molecules move faster, collisions happen more frequently so the substrate molecules enter the active site more often. Even more important is that when they collide it is with more energy that they do so; this makes it easier for bonds to be broken so that the reaction can occur. As the temperature continues to increase the speed of movement of the substrate and enzyme molecules also continues to increase. However, above a certain temperature the structure of the molecule vibrates so energetically that some of the bonds holding the enzyme in its precise shape will begin to break. ...read more.

Middle

By identifying and adjusting errors in the method and taking the limitations of the equipment into account a new method can be proposed which minimises significant sources of error and promotes attaining reliable results. Suitability and accuracy of each piece of equipment: Water baths: For temperatures 20�C to 50�C water from kettles were used for water baths and the temperature was brought down by the addition of tap water. For temperatures 60�C and 70�C electrical water baths were used. This was already posing a large threat to the fairness of the practical. The kettle water bath temperatures were not kept constant like the electrical water baths. This meant that the enzyme was not necessarily working at the temperature being examined. Also, the method of using the water baths was faulted. The method states to add the bottle of milk and trypsin tot the water bath once a constant temperature has been reached. This meant that the actual temperature the enzyme was working at had not yet adjusted to the required temperature. As the required temperature got higher the more time the enzyme-substrate solution needed to adjust to the temperature. However time for this adjustment was not taken into account, resulting in a massive inaccuracy. A suggested improvement is to use electrically controlled water baths for all of the temperatures tested and to allow for the enzyme-substrate solution to reach the temperature of required reading, equilibration. ...read more.

Conclusion

Therefore this method had a fairly low degree of accuracy. Timers: This piece of equipment has a degree of accuracy to 100th of a second, however the method under which it is used is also imprecise. The question is whether to start the timer when the first drop of trypsin hits the milk or the last drop, and is it physically possible to do these two things at the exact same time. However it is difficult to suggest improvement, unless you could get a partner to start the timer just as the first drop of trypsin hits the milk so that there is a more precise reading without a gap in the time it takes to move from the syringe to the timer start button. Repetition: There was no mention of repetition in the method for this experiment. Indicating that any of the results could be anomalous and none of them can be guaranteed as accurate. This method therefore rules out human error. However this may be accounted for when a graph is drawn up. Anomalous results can be singled out and in this case there is certain fault in the shape of the graph. After identifying many sources of error within this experiment it is clear that the validity of the evidence is challenged and will mean any conclusions drawn from this experiment will be imprecise and have little evidence to support them. ...read more.

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