Graph 2
The graph of rate of reaction against temperature did show that the 2 factors were proportional, but only up to a point. After 60 degrees Celsius the next temperature measurement showed that the reaction did not occur. I believe that this is because at some point between 60 to 80 degrees Celsius the Trypsin enzyme became denatured, (this is where the heat distorts the enzyme in such a way that stops it from functioning).
While it is said that rate of reaction and temperature are directly proportional this is not completely true. The graph plotted shows a slightly curved line from the reading at 20 degrees Celsius to the reading at 60 degrees Celsius, (the region of the graph that I believe shows direct proportion). I believe that curve is caused by some of the trypsin enzymes denaturising at a lower temperature, leaving the bulk of the enzymes to react proportionally faster until after 60 degrees Celsius. I believe this is why the effect becomes more prominent as the temperature continues to increase, (as more of the enzymes are likely to denature earlier than 60 degrees Celsius as there is a wider range of temperatures for them to denature at).
From the graph it is clear that the fastest rate of reaction for the trypsin is when the temperature is at 60 degrees Celsius. When the temperature is at this level particles have more energy and so more collisions, (resulting in reactions) will be made between the trypsin and the proteins in the milk, meaning that the reaction occurs at a faster rate. This is true according to the collision theory which states that the more heat energy particles have the faster a reaction will be undergone.
Scientific Theory
Trypsin is a biological catalyst, (a substance that speed up a reaction without being used up or changing the reaction in any way), known as an enzyme that is found in the human body. Trypsin is a protease enzyme, which means that it digests the proteins in food that is consumed. However humans, (as animals themselves) are constructed largely of proteins.
This means that unless stopped trypsin produced in the pancreas would digest the proteins that make up the body itself and indeed all of the body’s enzymes as well as the proteins digested in the digestive system. This is why trypsin is not produced in its active form.
Trypsin breaks down proteins by separating the long chains of amino acids that form the proteins into smaller ones. This occurs when a Trypsin enzyme comes into contact with a protein. It is believed by scientists that the enzymes function by fitting onto substrates, (because of a specific shape an electric change they bear) and undergoing reactions to split or link the substrate.
As contact is needed for enzymes to react with substrates the impact theory, (which states that reactions occur when substances bump into each other) suggests that the higher the temperatures at which substances are left to react with each other, the greater the chance of reaction, therefore the faster the rate of reaction. This however is only true to a certain level, as after a point enzymes denature. Denaturing is when the enzyme, due to it being formed of proteins reaches a temperature where it can no longer hold its shape and it warps so that it no longer fits the substrate it is supposed to react with. In the case of most enzymes this occurs at around 50oC.
Enzymes are all designed to operate best at a specific temperature. For example enzymes in the human body such as trypsin operate best at around 37 degrees, as this is the average temperature of the human body. The temperature at which enzymes work best at is known as the optimum temperature.
Evaluation
I believe that the results recorded for the experiments undergone are reliable enough to base my conclusions upon. I believe that a suitable procedure was followed that ensured that all inaccuracies in readings occurred due to human errors in reading. A syringe rather than measuring cylinders being used avoided errors in the measurements of volumes of solutions. This left no room for inaccuracies in not accounting for the meniscus as a syringe will leave no room for a meniscus and bears detailed volume readings, (to the nearest tenth of a cm3). This procedure yielded fewer inaccuracies meaning that results were more reliable.
It was found out that the protein test used to determine when a reaction had finished did not function. This may have been due to the trypsin enzyme itself being a protein, however I believe that the test did not function correctly anyway as the solution used was supposed to start purple and change colour when protein was added, instead it turned blue and remained that colour indefinitely. Due to the protein test not working another system was employed whereby the transparency of the solution was gauged by observation. This meant that there was a larger error margin as to the definition of when the experiment had finished. Though this affected the accuracy of the results recorded I believe that the conclusions drawn were still accurate, as there was a large time difference between the results from the different temperatures that could not be mistaken even if the results were only accurate to the nearest 10 or 20 seconds.
I believe that my results show no anomalies, as the results shown on my graphs show simple trends with no obvious exceptions. Due to this continuity of results, (drawn from my graphs), I believe that my findings are accurate enough to base my conclusions upon.
I believe that the investigation could be further explored by experiments being performed at 10 degrees Celsius temperatures intervals ranging between 0-80 degrees Celsius. This would help to verify trend in the results and would show to a greater degree of accuracy the exact temperatures at which the reactions cease to occur. The results would show more accurately how steep the curve from the optimum temperature past the point of denaturisation to the point where the reaction doesn’t occur is. This would show more accurately the temperature at which the reaction stops occurring. Equally the point at which the trypsin is dormant, and does not react at could be ascertained to a higher degree of accuracy.
Bibliography
A revision website used to define key terms and use correct scientific terminology:
Website used to identify link between two factors:
Another website used:
Website for information about trypsin:
Knowledge I have learnt through the teaching of B4
OCR 21st Centaury Science textbook
OCR 21st Centaury Science revision guide
