prediction. I have predicted the collation between the rate of reaction and the
temperature because of the collision theory. The collision theory is affected by the
temperature of the solution. If the temperature is high the chance of a successful
collision is increased. This is because the extra temperature supplies extra energy to
the particles. The particles must have a certain amount of activation energy to have a
successful collision. In this case the trypsin will collide with the gelatine and attach
itself to it. Trypsin must break the gelatine to succeed in clearing the film. The
enzymes do denature at higher temperatures so the reaction should slow down. When
an enzyme denatures it stop working and in this reaction it should stop. However the
gelatine doesn’t need trypsin as it dissolves at high temperatures. Below there is a
diagram of how a substrate and an enzyme fit together. Enzymes have a particular
shape and this shape can only fit into one substrate. In the lock and key hypothesis the
enzyme is the key and the substrate is the lock, the place at which the enzyme and the
substrate meet is called the active site. At lower temperatures, generally below 50oC
the enzyme and the substrate fit together like a lock and a key. However, when the
temperature increase the enzyme denatures and the shape of the enzyme alters. Now
this enzyme cannot fit into the substrate. Each enzyme has a specific substrate so if
the enzyme cannot fit then the enzyme is useless and doesn’t act like a biological
catalyst, anymore. The reaction however will still continue to rise as the gelatine will
dissolve at high temperatures.
Apparatus
- Splint
- Test tube
- Photographic Film
- Trypsin
- Thermometer
- Stop Watch
- Water
- Measuring cylinder
- Kettle
- Small pan
- Pipette
- Pipette fillers
Diagram
Method
We started by laying out all of the apparatus according to the diagram above.
We had to do this experiment at 6 different temperatures, however we did the
experiment at 7 as this would allow us to make a mistake and still be able to complete
the experiment. We also did each of the temperature 3 times so that we could remove
any anomalous results, we would remove the anomalous result by taking the average.
We made this test fair by keeping all the factors of the experiment the same apart
from the temperature. For the safety precautions we used goggles as Trypsin can be
dangerous if it was to go in to the eyes. This is the step by step procedure that we
employed to complete the experiment:
- We took a piece of the film that was pre cut to 1cm x 1cm, and placed it between pieces of cut splint.
-
We took 10ml3 of heated kettle water and 10ml3 of Trypsin and put them into a test tube.
- We heated a kettle and poured the water into a small pan.
- We put the test tube inside of the small pan and monitored the temperature of the solution inside of the test tube.
- We waited until the temperature was the temperature that we desired.
- We took the splint with the film and placed it in the test tube. At this point we started the stop watch.
- One of our group members agitated the film so the reaction will take place faster, however this person stayed the same throughout the whole investigation as it had to be a fair test.
- Another member of the group watched the film, this is because we had to find the precise moment in which the film goes clear.
- At this point the person with stop watch stops timing and copies his results in a diary.
- This experiment has to be repeated 3 times for each temperature.
- The temperatures that we produced are 20, 30, 40, 50, 60, 70 and 80.
Results
Results Average
Conclusion
My graph has begun to show a trend. At 20 oC the time was 156 seconds however at
40 oC it is 83 seconds. This shows that as the temperature increases the time
decreases. This is because reactions at high temperatures have more collisions, like I
have stated in my prediction in the form of the collision theory. As the temperature
gets higher there is more energy present in the reaction. So therefore there is more
activation energy. If there is more activation energy then there is a greater chance of
having a successful collision. If there are more successful collision then there are
move bonds broken. Therefore the rate at which the reaction occurs will also increase.
However some reactions have different activation energies. All in all I feel my
prediction was correct.
Evaluation
My results show that my prediction was correct. I can see this as my graph shows the
correlation between the temperature and time it take to complete the reaction. The
graph also shows that the reaction kept on occurring even though the Trypsin has
denatured. This is because the reaction keeps on occurring at higher temperatures.
Gelatine is insoluble, however if it comes it to contact with water at high temperatures
it becomes soluble. Luckily I did not receive any odd results as my graph is smooth
and free flowing. My method was easy to follow as it had a step by step layout. It
also covered all the components to this experiment, to make it easy to do the
experiment without making mistakes. My results however could have been made to
be more accurate. I could have used a graduated pipette so the amount of Trypsin that
was put in would have been more accurate, this is because it had a smaller scale than
that of a measuring cylinder. I also could have used a water bath. If I had used a water
bath I could have kept the water temperature at a constant. I could have also used a
water bath that contained a stirrer. We did have enough time to complete the
experiment as we were getting three test tubes at the same temperature. To make the
experiment even more accurate in the future I could use an electronic thermometer.
This will benefit the experiment in two ways, one way is to stop the misreading of the
temperature and another is the more accurate reading of temperature as a thermometer
can be hard to read in some situations. Some aspects of this experiment did prove to
be difficult. For example achieving 85 degrees Celsius was difficult as it could only
be achieved for a sustained time, however in this time the experiment could take
place. The next time I do this experiment I will make the size of the film strips larger
because if the surface area of the film was greater, the timing of the experiment will
be easier. Another reason for our experiment not being so accurate, may have been the
stirring of the photographic film. This could have changed our result as one piece of
film could have been stirred faster than another. The trypsin molecules may have been
moving faster and may have been hitting the gelatine layer much harder and more
often, therefore the film would have cleared more quickly. This could have been
rectified by using a mechanical stirrer, this would stir the mixture at a constant speed.
If I could do another experiment linked with this I would see how much film could be
economically cleared by a particular amount of trypsin. This can be used to make
clearing film economically viable. I think the experiment was reliable for me to state
my conclusion. As think this because there were very few anomalies.
Bibliography
Unilever Education Advanced Series: Proteins