Results
Here the tables of my results, along with another two groups. Here are my results first.
Here the second groups.
Here is the third group’s set of results.
The graphs I made from results are on a different piece of paper. Along with a time graph I have also done a rate of reaction graph. The rate of reaction graph will be more accurate as I am measuring the arte of reaction. I have found some anomalous results in my results table, which I will explain now. I have circled them in red. The reason for the anomalous results at 40ºC was that we had to use a Bunsen burner, as the temperature did not remain constant and fluctuated. To keep it the right temperature, we needed to use a Bunsen burner. As heat does not travel well in water, not all the water become hot, but the part that did became extremely hot and so could have altered the temperature. This would have had an effect on the results obtained. Sadly we did not have enough time to do another test at the same temperature. We also obtained anomalous results at 60ºC and 65ºC. The reason for the anomalous results at 60ºC was because one of our test tubes was of a different size and so was not submerged under the water, giving a false result. At 65ºC, we had to use a Bunsen burner, which like the 40ºC may have altered the temperature because only part of the water was exposed to a high temperature.
To make this a fair test, I will use the same manufacture ad type of milk; I will use the lipase from the same animal, and I will use the same concentration of lipase, milk and sodium carbonate.
Safety procedures that I must take are to wear safety goggles when handling the hot water as it is steam and I may get scalded, and also to wear goggles when using the lipase, as it is corrosive. I will also keep the stools under the table preventing people from falling over.
Conclusion
Looking at my results I can see that although my results do not follow a pattern, but the other results I attained from fellow colleagues came up with a similar pattern. Although I should use my results I will talk about trends and patterns using the other group’s results. The trends that I attained from the graph I drew proved that there was a similar trend in the results. The slight difference in the graph is where the peak is in each curve. In my results, the peak is at 50ºC, but in the others they are at 55ºC and 60ºC. This may be the case, but the trend lines that they follow are the same, showing that there is an optimum temperature to the lipase, and anything below that it works slowly, and anything above that, the enzyme starts to work slowly and then becomes denatured. The rate of reactivity altered in different temperatures because the heat gave the energy, and depending on how much heat was given depended on the energy. This backs up my theory as I stated about the Kinetic theory and the Collision Theory.
Enzymes have factors that affect the rate of reaction. They are the concentration of the lipase, the concentration of the substrate and the temperature. I investigated the temperature. To understand how the temperature affected the rate of reaction and gave me the results I achieved, I need to see what enzymes are and how they work. An enzyme is a biological catalyst that speeds up reactions without chemically changing itself. They have an active site that connects the substrate and the enzyme together. It is here that the enzyme breaks the substrate down, making it easier for it to be absorbed into the blood stream. Here is a diagram of the enzyme breaking a substrate down.
This diagram shows what is happening to the fat in the milk. When an enzyme is not present, there is an energy barrier preventing the molecules in a cell from reacting more than occasionally to form products. An enzyme gives more chance of this happening by temporarily combing itself with the molecules of the substrate and making them more reactive. In this way, if there is more heat then the molecules will work faster as they have more energy. At higher temperatures this happens, but if the temperature exceeds the optimum temperature a lot, then something different happens. The reason for the reaction going slowly at a temperature below 50ºC is because there was enough energy at such a low temperature, even if there was an enzyme there. At temperatures above the optimum temperature, which were different in my graph, the enzyme became denatured. The rate was higher at the higher temperatures (up to 50°C) because as the temperature is raised, so is the energy level of the enzymes and substrate molecules. This is where the greatest number of collisions takes place between the enzyme and the substrate and therefore the highest rate of reaction is. This means that they have more kinetic energy so they collide more often and therefore more reactions take place between them. The enzyme denatured at about 70°C because the weak bonds, which hold the molecule into the specific shape for one substrate, are broken. The increase in molecular collisions and vibrations at higher temperatures is great enough to permanently change the shape of the active site. The enzyme is said to be denatured because it can no longer form an enzyme-substrate complex as its active site has been unalterably changed. Another reason for the way enzymes act at lower temperatures is because they are protein based and so react like them, and are damaged by excessive heat or cold, as well as acidity. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate.
My prediction, though wrong as I predicted the wrong temperatures, was right in the sense that I had said that at lower temperatures than the optimum temperature, the rate of reaction would be slower, and higher than the optimum temperature meant that the rate of reaction would slow down and then stop completely at high enough temperature. I have given reasons for why this occurs. As I did not get a proper set of results, as they were mainly anomalous, I can see that in the other groups the optimum temperature differed and so I cannot really say what the optimum temperature was as the results varied.
Looking at my results on the graph, I noticed that some were very anomalous. This was because I was not able to repeat the temperature and get better results. As I explained in my results I justified why the results were anomalous. This was carried onto my graph and so they came out anomalous if we draw a trend line with my results. Also looking at my results, I can see that apart from being very inaccurate, they are also very unreliable. I used two groups’ results to see if similarities lay in their results and the compared my results with theirs. I will explain more of this in my evaluation.
I conclude that my results, although inaccurate and unreliable, did follow a general trend that backed up my prediction. The results I obtained helped me to understand more about enzymes and their behaviour. As well, the pH for lipase is alkaline as it is in the duodenum, for the reason that one of the products is fatty acids, and if the pH were high as it was, then the gut wall would be attacked and destroyed by the acid.
Evaluation
The method I used was suitable, although it did lead me to get a fair few anomalous results. These anomalous results would draw me to the conclusion that the method was unsuitable, but as I used two other groups’ data, I could see that the method was suitable for them. I followed the method accurately, but still managed to get anomalous results, which show that there was a flaw in the concept. There was a flaw in that there were only two people, and if there was maybe one more person, it may have gone well. Everything was fine until we had to add the lipase. I had to somehow manage to put lipase into two test tubes without it going everywhere. This was quite unsuccessful and may have contributed to the anomalous results I obtained. Also, I used different milks over the days (the same type though), and so the fat concentration may have varied over the days, as I could not finish it in one day. The phenolphthalein was not really an accurate way of seeing when the fat had been digested. It was difficult to see when the colour had changed and I was not sure whether the transition had been fully completed. In the actual experiment, the control had phenolphthalein in it, so all we had was to compare it with a purple solution. This would have been easier if we had had the original colour of the milk to compare it to, as then I could have fully recognised the transition from purple to colourless.
As I have pointed out the inaccuracies in this experiment, I will see how I can overcome them if I was to repeat this experiment. I would change the group to three, as then not one person has to try and put lipase into two test tubes. I would also have liked it if we could have done the experiment in one day as I would have used the same milk and hopefully have got continuous results, as the concentration would not have really differed. This may have allowed me to get some reliable results. Instead of using phenolphthalein I would have used a data logger that would have measured the change in pH. This would have been more accurate. I have enclosed a graph showing the change in pH at 25ºC. You can see when the lipase has been added, (at 2 minutes). This method is better than judging by eye and seeing whether the colour had changed, because not everybody will agree in a colour and so each group would obtain different results. Also, to obtain even more accurate graph, I would check the rate of reaction at every 5ºC. This would help me to see where the optimum and the denaturing temperature easily.
The trends I acquired from my graph were not enough to draw firm conclusions, as the trend line is the path my results should have followed, but many of them were anomalous. My results were so inaccurate and unreliable that my conclusions were based on the results of the other two groups. Their results were consistent, and were generally consistent with my prediction and so I was able to draw firm conclusions from their trends. The difference between the two results mainly lay in their optimum temperature. As they found different temperatures I was unable to say how wrong my prediction was. Even though, I was still able to come to the firm conclusion that an enzyme has an optimum temperature where its rate of reaction is the highest, and any temperature below that, the rate of reaction will be a lot slower. A higher temperature will cause the enzyme to become denatured. This conclusion was consistent with my prediction.
This experiment could be extended to see how different types of milk may affect the rate of reaction. I could also see how different pH’s affected them to. To carry on the work on temperatures, I could see how low does an enzyme work. I could find out the lowest temperature recorded of a human being, and try and see how it affects the rate of reaction of the lipase. Also, this could be tried with different types of enzymes, for example using potato discs with amylase.
This experiment helped me to learn a lot more about enzymes and how the function under some circumstances. It also helped me to learn how I can improve my obtaining results section. Although it was almost a suitable method, the fact that I obtained anomalous results shows that it was not that reliable. Also many people did not get accurate results, as the equipment used did not allow us to acquire accurate results.
It is important that we find out about enzymes and their actions as we use them in our everyday lives. Apart from living in our bodies and breaking up large molecules, enzymes are used for other important things. These are included in industrial and medicinal. They are needed for the fermenting of wine, leavening of bread, curdling of cheese, and brewing of beer. In medical usage, they include the killing of disease-causing microorganisms, the promotion of wound healing and the diagnosis of diseases. They are also needed for washing-up powder, to break down food stains, and also to be synthesised to produce more enzymes for people who cannot manufacture it themselves. If wee do not understand enzymes, then we will not be able to use them when we need to do. This would cause us to fall back in our progress in science. As well as these reasons, we use enzymes everyday and so we need to understand how they work so we know where to use them. They are also living inside us and many people like to know what is going inside themselves.
This investigation was very helpful and informed on new things that involve enzymes. It also helped me to see that changing the temperature will affect the rate that the enzyme breaks down the substrate, which affects our body.