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The effect of Temperature on the rate of Enzyme Activity.

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Biology Practical Assessment: The effect of Temperature on the rate of Enzyme Activity. Interpretation of Results: Table to show the effect of temperature on the rate at which rennin solidifies the milk protein caseinogen. Temperature /�C Time taken for milk to set/s Mean time/s Mean rate/s-1 x1000 1 2 3 4 5 6 7 8 9 10 11 35 255 255 210 255 180 210 240 240 180 240 225 226 4.4 39 120 135 90* 285* 120 105 105 165 105 120 120 134 7.5 44 90 180* 120 225* 60 60 90 75 90 105 105 109 9.2 49 45 105* 90 90 75 45 45 75 45 90 90 72 13.9 60 NR NR NR NR NR NR NR NR NR NR NR NR 0 Anomalies* Trends and Patterns: Up until 60�C, the general trend of the graph shows that as the temperature increases, the rate at which the milk solidifies increases. When the temperature was at 49�C, the rate was highest but above this the rate decreased until it reached 0 at 60�C. Between 35 and 39�C, the rate increased from 4.4/s-1 x1000 to 7.5/s-1 x1000. However, between 39 and 44�C the rate did not increase as much and this is shown on the graph as the gradient between these points is not as steep as between 35 and 39�C. ...read more.


However, although the temperature increased up to 60�C, the rate began to decrease rapidly after 49�C. This is because the rennin particles began to vibrate and this caused strain upon the ionic bonds which became so great that the bonds broke. Consequently, this caused the shape of the tertiary structure to alter- and therefore the shape of the active site. As the shape of the enzyme's active site had been altered- or denatured- it was no longer complementary to the substrate- or caseinogen and so no enzyme-substrate complexes could form, and in turn no products- insoluble casein- could form, therefore bringing the rate down to 0/s-1 x1000. Evaluation: Although the graph shows the general trend expected when temperature is the independent variable on enzyme activity, there were some anomalous results within the mean times used to calculate the rates. For the reactions at 35�C I did not highlight any anomalies as although the times recorded ranged from 180 seconds to 255, the mean result was 226 and this falls somewhere in the middle of this range. Furthermore, although 180 seconds seems very low in comparison with a mean result of 226 seconds, two groups recorded this time and so I believe it is no completely anomalous. For the rennin-caseinogen complexes incubated at 39�C, there were two clear anomalies in comparison with the mean time of 134 seconds; one anomaly was 90 seconds and the other 285 seconds. ...read more.


The third most significant reason for any anomalous results could again be down to differences in procedural technique between groups. The rennin and milk were combined after incubating separately but whereas some groups would have shaken the tube to ensure a homogenous solution, others may not have. As a result some enzyme molecules would have just remained on top of the solution and when heated would not have been able to bind with the caseinogen. This may have been the case for group 2 who recorded 105 seconds for 49� whereas the mean was 72 seconds. The only way of improving this would be to ensure that all groups made an attempt to homogenise their solutions by shaking thoroughly before heating. However, the reason for ranking this third is that the heat would have caused the molecules to gain more kinetic energy and to therefore the probability of them colliding to form rennin-milk complexes would be dependant on this. The least significant reason for anomalous results would be biological variation between the milk samples used. This could be an error as here may be differences in pH between different breeds or individuals. However I believe this is unlikely to cause any major anomalies as all groups were told they were using full fat milk and furthermore, the samples of milk would not have some from single cows, but from a batch which would have been mixed to produce a homogenous solution. ...read more.

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