I took great care with the experiment because I was dealing with hot liquids.
Apparatus
- 27 photographic strips (substrate), each measuring 0.5cm x 35 mm
- 3ml protease (trypsin)
- Wire
- Test tubes
- Water bath
- Thermometer
- Stopwatch/timer
Method
I measured the time taken for the film to become transparent at different temperatures – this demonstrates whether or not the effectiveness of the enzymes increases or decreases with heat.
I first switched on the water bath, setting it to 35ºC. I then measured out 3ml of trypsin into the test tube, placing it upright into the water bath. I bent both ends of the wire into tiny hooks, threading the photographic strip onto one end. Then, when my thermometer told me the water had reached 35ºC, I suspended the wire into the trypsin using the other end of the wire as a hook over the side of the test tube.
Immediately the photographic film was put into the trypsin, I started my stopwatch, stopping it when the photographic film became transparent and immediately taking the photographic strip out. I noted down the time it had taken and entered it into a table (see below). Using a fresh photographic strip, I repeated this part of the experiment twice more, to give me three readings against each temperature, from which I could then take an accurate and meaningful average.
I then turned up the temperature of the water bath at 5ºC intervals, recording the results again three times each. I ended my experiment when the temperature reached 70ºC.
Fair Test:
I ensured this was a fair test by doing the following:
- Doing all the tests on the same day because sometimes there are conditions out of our control that can change
- Checking with universal indicator paper that the pH value of the trypsin was always the same, because enzymes denature when exposed to pH values greater or less than seven.
- Checking that the concentration in the test tube was always the same: 0.5% trypsin, to ensure balanced results
- Making sure the temperature on the thermometer was exactly as it should be when recording my stopwatch results
- Using the same type of photographic film and the same height and length
Predictions
I think that as the temperature increases, so will the enzyme’s rate of reaction, but I think when it gets to a certain temperature, the enzymes will begin to denature and will not react as quickly.
I think this because in my research I found that all enzymes are proteins and at high temperatures, protein breaks down. This changes the active site so the substrate can no longer fit, denaturing the enzyme.
Results
Time taken for film to become transparent
* temp = temperature
Conclusion
In order to see the results from my table more easily, I converted them into a graph. From the graph, I could clearly see that, on average, trypsin enzymes work best at temperatures of 40 - 60ºC, because it is then that the film turns transparent fastest, shown on the graph as a flattening-out.
The graph also shows that the enzymes then start to denature at around 65ºC because the line shoots up. Here, the film takes radically longer to become transparent, eventually causing the trypsin to have no effect on the photographic strip.
A line of best fit would only be appropriate between 45 and 65ºC.
These results fitted in with my predictions because the enzymes did increase their rate of reaction when the temperature increased and did denature at a high temperature.
Evaluation
I thought my experiment worked well because it showed similar readings and I didn’t have any odd-looking figures within the results. I also thought the results were accurate enough, because it gave such a clear pattern of the enzymes’ behaviour.
If I wanted get obtain even more accurate results, I could have tested at an even greater number of temperatures.
I think my method was the best way of carrying out the investigation because I took more than two results to reach my conclusion. I could improve my method by taking even more results.
To provide me with even more evidence for this investigation, I could compare notes with other students who have carried out the same experiment, to see if there are any anomalies.
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