Investigating the Effect of Temperature on Enzyme Activity

Risk Assessment:

* Hydrogen Peroxide (H2O2) is an irritant and dangerous if swallowed.

* Wear eye protection.

* Avoid contact with skin and clothes.

Results:

Temperature °c

Rate at which the

oxygen evolved in

cm3per min-1

Mean Rate

2

3

5

0.6

0.2

No result

0.4

25

2.2

2.6

No result

2.4

35

2.6

2.5

2.6

2.6

45

2.0

.8

2.2

2.0

55

.0

.0

No result

.0

Graph:

Analysis of results:

The graph and table of results both prove the hypothesis to be correct: The higher the temperature, the faster the reaction rate, until an optimum temperature is reached.

The figures in the table shows that as the temperature increased, the mean rate had increased steadily until 35ºc, after which the mean rate started to decrease. This is because the optimum temperature for enzymes to work at is around 38ºc. Temperatures exceeding this will denature the enzyme; therefore the enzyme is unable to function properly, hence a decrease in the rate.

The graph shows the points at which the enzyme activity is steadily increasing and when it starts denaturing. The rate increases very fast between 15ºc and 25ºc, showing that the enzymes are most active at this point. From 35ºc onwards, the enzyme activity starts decreasing due to the denaturing of the enzymes, therefore a dip in the curve. The rate falls fastest between 45ºc and 55ºc because the enzyme is no longer able to function properly. At higher temperatures (20ºc - 40ºc) the enzymes are able to work faster. More successful collisions take place due to an increase in kinetic energy, this results in an increased reaction rate, however after the optimum temperature is reached, the enzyme deactivates, so to say it denatures, hence the reaction rate decreases, thus a lower rate of activity.

Evaluation:

In the experiment, there were no anomalous results. The experiment was suitable to test the hypothesis because it proved it correct and this is clearly shown in the graph and table. However there were a few problems with the experimental design:

) There was not a constant mass of peas used; this was a random error. To overcome this, grind the peas so that 2g of peas was used each time. Weigh the tube before and then after adding the peas, so that exactly 2g is being used. This is better because everyone gets the same amount and also because the mass will stay consistent, therefore the variables will be more controlled.

2) The way in which the peas were crushed was not controlled either, and this once again was a random error. To control this, a blender could be used to crush the peas, timed for 10 seconds. By doing this, the surface area of peas being exposed to the hydrogen peroxide would stay constant.

3) Gas was also leaking from the bung of the test tube. This was a type of systematic error. To minimise the effect of this, tape the seal around the bung, this secures the bung therefore preventing the gas from leaking.

Conclusion:

The experiment proved my experimental hypothesis to be correct and disproved/ rejected the null hypothesis. The null hypothesis stated that temperature had no effect on enzyme activity, however the results showed that as the temperature increased, so did the enzyme activity, until an optimum temperature was reached. In conclusion, enzyme activity was affected by temperature.

Zoya Khan Biology Investigation- Janet Taylor 18-04-2007