The graph above shows that as the temperature rises the enzyme activity increases. This means that the number of collisions between reactants and enzymes also increases up to the optimum temperature.
The graph then continues to show that after the steady increase in temperature, collisions still continue to collide but the enzyme molecules denature due to the increasing temperature and at a much slower rate. Different enzymes have different optimum temperatures and I predict that my final graph should look like the one above but I will use a dotted line around the top curved area because my results won’t be accurate enough to pinpoint the exact optimum temperature.
Method for Final Experiment
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I will count out 15 potato discs into a test-tube, and then measure out 10ml of hydrogen peroxide into another test-tube.
- Putting them to one side I will then prepare a small beaker of water at a desired temperature and place the two test tubes inside.
- I will leave them for approximately 5 minutes in order to adjust the temperature of the contents of the beaker.
- After 5 minutes has commenced I will pour the hydrogen peroxide into the test-tube containing the potato discs and connect the tube leading to the gas syringe and also start the timer.
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When 10cm3 of gas has been collected in the tube I will stop the timer.
- This process will be repeated for all the desired temperatures I require plus three times over in order to gain an average and keep this a fair test.
Is it a Fair Test?
I will make the experiment a fair test by controlling and changing certain key factors.
- I will use the same number of potato discs each time.
- I will remain to use 10ml of hydrogen peroxide of the same concentration.
- I will always make sure the potato and the hydrogen peroxide are at equal temperatures.
- I will be varying the temperature.
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I will only time how long it takes for 10cm3 of oxygen to collect in the gas syringe.
Varying the Temperature
The different temperatures I will be using are:
10, 20 (Room), 30, 40, 50, 60 and 70°C. I will take results from these temperatures 3 times and then derive an average result from them. I will measure out all the products using the right equipment and using a level table to ensure it is accurate.
Is it a safe test?
As we are using harmful substances, to ensure safety I will follow the concluding rules:
- I will tuck in my tie, and remove my blazer.
- I will wear gloves when handling the hydrogen peroxide.
- I will wear goggles throughout the whole experiment.
- I will take great caution when using the hot water baths.
- The hydrogen peroxide I use will be of a low concentration as it is a very violent substance and may blister the skin if contact occurs. Also if a high concentration of it gets hot, it may become more harmful.
RESULTS
These results below are the ones collected from the final experiment:
The result in read is anomalous and will be explained in my evaluation.
This table shows the reaction rates of the experiment:
From this table above, the highest rate of activity is at the temperature of 40°C and these results show very clearly what I predicted earlier in my hypothesis. My hypothesis stated that the best temperature to keep the enzyme Catalase working at is 40°C and anything higher than this optimum temperature will decrease because the enzyme has denatured.
My two graphs portray this theory clearly. The first one is showing the increase in the release of gas is affected by the increase in temperature and the second graph is showing the energy levels of the enzyme throughout the reaction and how it peaks at the optimum temperature of 40°C
We conducted the experiment at 60 and 70°C but due to this temperature we did not get any results. This is because the enzymes were very likely to have denatured and we can say this because of our background knowledge.
Conclusion
Our results are accurate enough to show that my prediction was very correct, and the enzyme Catalase works best at an optimum temperature of 40°C. Also from my results, I can see that the extreme temperatures are not so different in action. As the temperature increases from 0°C the time that it takes for 10ml of oxygen to collect in the gas tube decreases slowly until it gets to 40°C which is where it reaches its lowest time at 56.3 seconds. This means that the enzyme works best at around 40°C.
When we conducted the experiment at 60 and 70°C we had no results at all because it just took too long to get to 10cm³ because the enzyme had denatured in the extreme temperatures. From this experiment, I can now conclude that varying a factor such as temperature can affect the rate of reaction of an enzyme extremely well. When these factors are changed accurately, the rate of the reaction will be manipulated very well.
This is scientifically proven by the ‘Theory of Collisions’. As the temperature of the Hydrogen peroxide is increased, the energy levels of the molecules start to increase and there are more successful collisions because of the increase in movement and therefore a rising reaction rate. But nature controls the energy levels by designing each different enzyme to denature at different temperatures and from my results it seems that once an experiment has reached a temperature of around 50°C, it slows right down. More collisions of molecules occur but the enzymes become denatured by the heat and that decreases the enzyme activity until they completely slow down and stop working.
EVALUATION
During this investigation we encountered a couple of areas that could have caused the anomalous results and could be improved. I will list these below.
Change in Temperature.
During the whole time that we undertook the experiment there could have been a vast change in temperature in the room that we weren’t aware of. This could have included the heating coming on, 30 people warming the room from inhabitancy etc. This could have caused a difference in temperature between the individual tests, which would have altered the rate of reaction. Also because the reaction gave off heat (exothermic) the conical flask may have heated up and the heat energy may have remained in the glass, therefore altering the temperature for the usage of the flask. This could be resolved by instead of just conducting the test within the water baths, trying to insulate the tank more so that the temperature could not change and remained accurate. This would make the glass keep its temperature to a desired one, and we would then have a constant of temperature for the entire experiment, this would also be an appropriate solution for a change in temperature in the surroundings.
Result Taking.
I think that if we took results at narrower margins we may have found that certain conclusions I have come to may be different. This could alter the whole outcome of an experiment. For example a margin that we could change would be the amount of different temperatures we took readings at. We conducted the experiment at every 10°C up to 70°C. We could have altered this and conducted the experiment at every 5°C.
Certainty
Without some of the issues I have discussed above my results would be very accurate, but those issues did exist and as a result of them on the whole there were quite a few strange results. But disregarding the anomalies the results I do have still manage to prove my prediction. With scientific evidence to back up my prediction my results prove it. Also my graphs show that the optimum temperature for the enzyme to work at is 40°C., but even if the experiment had gathered more accurate results I would have still been brought to the same conclusion that the optimum temperature for the enzyme to work is at 40°C. However this conclusion may have differed if we had conducted the experiment at narrower margins of temperature. We may have found it to be at 35 or 45°C.
We noticed an anomaly in our results. At 50°C on our 3rd test the time taken to collect 10ml of oxygen was extremely high. Higher than the other two results we gained. This then increased our average. However it did not alter the trend too much as the other two results were very much the same. To avoid a result like this maybe two people should be responsible for timing and taking readings, as they may have been a delay in taking the result from lack of concentration etc.
Investigation variations
This experiment went very well overall, although the factors I have discussed above did not seem to accredit the method very well. The major weakness with the method we used was only the loss of gas during the process of connecting the bung to the conical flask this meant anomalous results could be recorded. The best way to solve this problem is not to adapt the current method, but to change it completely. I think that an alternative method of conducting this experiment would be to measure something other than the gas release. In laboratory, controlled conditions it is much easier to measure gas release but in a classroom, that certain method is unreliable. One idea is to measure the weight difference. This alternative method could be as follows:
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Place a conical flask containing a fixed amount of Potato in onto the scales.
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Take the weight of the flask and contents & add it to the weight of the fixed amount of H2O2.
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Keeping the conical flask on the scales add the H2O2 to the flask. Every 10 seconds you can take the reading of the weight as it decreases on the scales.
From this I can work out the weight difference.This difference will represent the content given off as gas and from this I can get a reaction rate, which is the goal I am aiming for.
