Prediction:
I am going to change the temperature that the trypsin works at. The time taken for the trypsin to digest the gelatine will change because of this.
I predict that the temperature that the trypsin works at best (and so the time that the gelatine is digested quicker at) will be about 37°C, because this is body temperature.
Hypothesis:
Trypsin is one of the three principle digestive enzymes which are called Proteases. the other two are Pepsin and Peptidases. During the digestion process, Trypsin acts with the other Protease enzymes to break down protein molecules to their component Peptides and amino acids.
Trypsin is produced in the pancreas but works in the small intestine.
Gelatine is a protein, and will be digested by the Trypsin.
I predicted that the trypsin will work best at 37°C. This is because enzymes break down the substrate by a method known as the “lock and key” method. The enzyme traps the molecules that they react with (the substrate.)
The shape of the enzyme is vital for this. To be effective, it must fit exactly with the substrate. It is often described as a key (the substrate) fitting into the lock (the enzyme)
If the temperature is too cold, the shape of the enzyme is altered slightly and the reaction cannot happen because there is less kinetic energy and fewer collisions. This is because the substrate can no longer fit the enzyme. But however, if the enzyme is warmed up again, its shape is restored.
If the temperature is too hot (above about 38°C.) then the shape of the enzyme is altered again, this means that the reactions are affected (slowed down or stopped)
But in this case however, the higher temperatures can permanently destroy the enzyme.
The best temperature, therefore is when the shape of the enzyme best fits the substrate molecule. For humans, our body temperature is 37°C as this is what our enzymes work best at.
Apparatus list
15 test tubes
measuring cylinder
pipette
5 water baths set up at 15°C, 25°C, 35°C, 45°C and 55°C.
Trypsin enzyme
Gelatine strip
Thermometer
5 stop watches
2 test tube racks
Tweezers
Method
Set up 5 different water baths at 15°C, 25°C, 35°C, 45°C and 55°C. These temperatures were decided with the help of my preliminary experiment and these are grouped around my predicted value for the best temperature which is 37°C.
Safety
- Wear safety glasses at all times
- Keep all test tubes, in the test tube racks.
- Keep the tables and floor area clear with stools under the desks.
Fair test:
Factors that will make the experiment fair.
- Same size of gelatine.
- Same amount of trypsin.
- Same pH level of trypsin.
- Keep temperatures the same in all water baths.
- If the temperature in the water baths goes over 60°C the gelatine may melt, which would lead to unfair results.
- Pickup the gelatine using tweezers as fingertips may damage the film.
Fill 5 test tubes with 8 ml of trypsin, using a pipette, then put 1 of theses into each of the different temperature water baths.
Use a thermometer to check to see if the trypsin has reached the temperature of the water bath.
Then put a strip of gelatine into each of the 5 test tubes. Start a stopwatch for each one at the same time as u do this.
When the gelatine strip is no longer black and goes completely clear in each test tube of trypsin, it means that the gelatine has been digested. Stop the correct stopwatch and record the time in a table.
Repeat this experiment, three times to ensure that any odd results are fixed so that the results are reliable.
Results
Averages:
25°C - 23.07mins.
30°C - 12mins.
35°C - 9mins.
40°C - 8.25mins.
45°C - 7.31min
Evaluation
Overall, I felt that the experiment went reasonably well. Although, it was not a perfect experiment I felt we got the results we expected. A result that doesn’t seem to fit can be seen in the result’s table where 55 seems to be the lowest. This is because when we obtained the data we saw that the film was clear but the solution was still murky, we only found out later that this meant that the solution hadn’t digested completely. We assume that this result is wrong as it does not fit any pattern. I felt the method that we used was a good method and helped us get most things right. The results have shown us that the enzymes work best at 35 , this may be because 35 is around the same temperature as body temperature, so enzymes would work better.
Analysis
The pattern I was expecting to see was something with a U shape, instead I got more of a W. This may have been because there was a wrong result which leads to me getting the W. As the temperature began to rise the speed of reaction increases until it gets to 35 ,then the speed starts to go down because the enzymes are then denatured. At 15 there is not enough heat to get the enzymes to work. At 35 this is almost the right temperature for the enzymes to work as it is almost body temperature. At 55 the temperature is too hot and some of the enzymes are denatured and unable to work.
