Prediction
I predict that the gelatine on the film will digest most quickly at 40o as this is around about body temperature and trypsin is found in the body. Also at this temperature the enzyme molecules should have enough energy, from heat, for sufficient successful collisions which means the rate of reaction will be very slow. At 0o and 20o the molecules will not have substantial energy. As the temperature goes above 60o, the shape of the enzyme change and the substrate can no longer bind with the active site. The substrate will no longer fit, the enzyme is denatured.
Preliminary Work
We decided which concentrate of trypsin solution we wanted to use. We had a choice of 3 strengths, 0.5%, 1% and 1.5%. We have chosen the concentration 1.5%. We chose this because it was best suited to the length of photographic film we used. We chose the length at 1inch because if we had decided on a very small piece the reaction would have been too fast for us to time, but if had chosen a long piece it would have taken too long and we would have taken a very long time for us to finish the experiment.
Factors
The factor we changed was the temperature, because we were studying the effect of temperature on enzyme activity. The concentration of the trypsin solution, the length of the photographic film and the amount of trypsin solution all stayed the same.
Fair Test
We made this a fair test by doing the experiment 3 times to get an average result. This made our experiment more accurate. If we had only done the experiment twice at each temperature the two results could have been totally different and with just two we would not be able to tell which one was wrong.
Apparatus List
-
5 cm3 1.5% trypsin solution
- 1 inch photographic film
- Test tube
- Thermometer
- Test tube rack
- Stop clock
- Water bath
-
Ice (only at 0o)
Diagram
Method
- Collect all the equipment.
-
Measure out 5cm3 of trypsin solution and heat in a water bath for 5 minutes.
- After 5 minutes add the photographic film to the trypsin.
- Place straight back into the water bath.
- Check every 15 seconds to see if the photographic film has turned transparent.
- When the film is transparent, this means all the gelatine has been digested.
- Stop the clock.
Safety
For safety we wore goggles so that the trypsin could not get in the eyes because it is an irritant.
Results
- The rate of reaction was calculated with the formula 1/t. Where t = the average time taken.
Conclusion
When the temperature was low (0oc, 20oc and 40o) the enzymes had little energy for successful collisions, which meant it took more time to digest the starch. At 80oc the enzymes had denatured which meant the substrate could no longer bind to the active site, which meant the starch took longer to digest. I expected 40o to be the best temperature for trypsin to work at as this is body temperature, but the best temperature was 60o. This means trypsin denatures at a higher temperature than other enzymes such as amylase.
Evaluation
My results did not quite back up my prediction, but only had one anomalous result, at 60o, which meant my method was quite reliable and accurate. This result could have been caused by human error for example forgetting to check on the experiment or not quite adding enough trypsin. This result could also have been caused by failures of equipment like a broken or slow stop clock, or a faulty water bath that does no stay at the right temperature constantly. To make my results more accurate could have looked at my experiment more frequently e.g. every 5 seconds instead of every 15 seconds. Room temperature fluctuates which could have changed some of the temperatures slightly, which would have effected results. I could have furthered my investigation by investigating ph instead of temperature as this would tell me the best ph for trypsin to work in. Also I could have used less/more photographic film or a weaker/stronger strength solution of trypsin.
