The optimum temperature for most enzymes is 40˚c, and after this they generally start to denature however, this is not always the case. The enzymes in the body have an optimum temperature and the body is adapted due to homeostasis to control this temperature so the enzymes are working at their best. Enzymes also have an optimum pH level where they work best at, and changes in this level can result in the denaturing of enzymes.
Hypothesis
I predict that a rise in temperature will coincide with a rise in the amount of bubbles up until 40˚c, and I think that after this the enzymes will denature and therefore, the amount of bubbles will fall. I can make this prediction on the basis that I have the findings of the Q10 theory so the amount of bubbles will roughly double every 10˚c I increase the temperature of the water and I think that this increase in the rate of reaction will stop and the enzyme will be denatured at 40˚c as this is the temperature closest to the bodies. Up until 40˚c the higher you raise the temperature the faster the molecules will move and the more collisions will occur. However, above 40˚c the enzyme will lose its unique shape. The active site of the enzyme will change and it will therefore not be able to break down hydrogen peroxide. The higher above 40˚c you raise the faster the enzyme will denature E.g. there will be more bubbles at 70˚c then there will be at 90˚c.
Apparatus
The apparatus I used when carrying out this experiment were: Hydrogen peroxide, 2x test-tube and beaker, borer, potato, delivery tube, ice, water, stopwatch, knife, ruler, thermometer, kettle, bung, syringe, safety goggles and tile.
Method
Trial runs were carried out so that I would know the exact amount of hydrogen peroxide and potato to use, and what the temperature margins should be. The results of the trial runs were:
From carrying them out these trial experiments they, helped me to decide what the best settings for my experiment were E.g. 1cm of potato was too small as it was totally immersed in the hydrogen peroxide, however when I carried out this same experiment but with 2cm of potato it was way too big to give a fair test. Next I chose to test 1.25cm of potato but it was also too small as it was immersed in the hydrogen peroxide so then I tested 1.5cm of potato and to me, this was the perfect length for which to carry out the experiment. I tested 2ml of hydrogen peroxide but I didn’t think that this was enough for the amount of potato I was using so I decided to do 3ml of hydrogen peroxide however, this also wasn’t enough. I tested 4ml of hydrogen peroxide and this was nearer than the other two, to the correct amount however it still wasn’t enough so lastly I tested 5ml of hydrogen peroxide and this was just the correct amount. With time it was not really the case of the time it was going to react best in but more a case of which was the time where it would react well but still have enough time to carry out a number of experiments. For the first experiment 1 minute was not long enough to get good results, so I decided to carry out the experiment at 1.30 minutes however this still wasn’t long enough to get good results so I skipped all the way up to 3 minutes and the potato reacted well however, this was too much time to spend on one experiment and if we used 3 minutes there would not be a lot of time to carry out experiments so, I tested it for 2 minutes and this left enough time for the potato to react well but also still left enough time to get a lot of experiments done.
Place goggles on face gather together 2 beakers and 2 test tubes. Put tap water in one beaker and get the temperature of water that you are going to use in the other. Use a borer to get a strip of potato and cut the potato strip into the desired length and put the capacity of hydrogen peroxide into a test tube. Fill the other test tube with water and place your thumb over the top to prevent gas escaping. Place the potato in the same test tube as the hydrogen peroxide and place a bung over this test tube. Place this test tube in the beaker with the water to your selected temperature and place a delivery in the other test tube while it is in the other beaker upside down start the stopwatch and read the amount of bubbles that come out. Repeat the experiment twice for reliability and to find an average. Do the experiment at various different temperatures at least 6 to see the difference that temperature makes. Make sure the temperature of the substrate has reached the temperature of the water that has been modified before adding the potato and as soon as the potato has been added start the timer.
There are also other methods which can be used these include measuring the mass of the gas lost but this type of specialist equipment is not readily available.
I will make sure that a fair test is conducted by:
- Using the same length of potato
- Using the same volume of Hydrogen Peroxide
- Washing and drying the test tube after each experiment has been conducted
- Using the same potato, as different potatoes will have different levels of catalyse present.
- Using the same concentration of Hydrogen Peroxide
- Using the same borer to cut the potato
- Washing and drying the knife after cutting each length of potato
I will make sure that the experiment is kept safe by:
- Always wearing safety goggles, as hydrogen peroxide can damage your eyes
- Not spilling the hydrogen peroxide as it is an irritant and bleaches
- Taking care when using the borer to get the potato strip
- Taking care when cutting the potato
- Taking care when handling hot water in a beaker
- Making sure that all substances are kept a safe distance from the edge of the table
Results
Experiment 1
Experiment 2
After compiling the results section it I quite obvious that there will be some very unusual averages.
Average Results
Analysis
From doing the investigation I have found out that the temperature of the room at the time of conducting the experiment is very important as one day when I conducted the experiment with the substrate at 90˚c there was 151 bubbles with a huge influx of bubbles at the beginning however when I conducted the experiment on a different day with the substrate at 90˚c again no bubbles were produced which means that the enzyme was denatured. I found this very strange, as I did not expect such a stark contrast from two different day’s results. This is a clear indication that the room temperature affects the rate of reaction.
From carrying out this experiment I cannot say at what temperature the enzyme was denatured at totally however, from the results I have taken on one day it was denatured at 90˚c and on another day at 10˚c. The optimum temperature for this experiment was 45˚c overall however on one day 70˚c gave off the most bubbles. Ii conclude that the most collisions occurred at 45˚c and this proves my prediction that the highest rate of reaction will be at 40˚c wrong however; I was not much out only 5˚c. This must have been the temperature where there was the correct activation energy. On the second run of experiments that I conducted I also realised that at the beginning of the experiments there was a massive influx of bubbles at the beginning of the experiment and I am not sure why this occurred. The Q10 factor could not also be proved in my work, as the rate of reaction did not approximately double as I increased every 10˚c of temperature. Even though my prediction was not proved 100% accurate it was proved correct to a degree as I expected the highest rate of reaction to occur at 40˚c however the highest rate of reaction proved to be, between 45 and 50˚c. This proves my prediction partly correct, as I was not far off. I think that this was due to the room temperature and some sort of human error by me.
Evaluation
I think in general the investigation was carried out well I wouldn’t say with complete success but I would say 90 out of 100%. I think I carried it out well but human error like not checking the temperature of the substrate just before putting on the stop watch however I think a valid conclusion was drawn from these results. I don’t think the results were clear enough for the investigation as there were many anomalous results and I don’t know how one day the enzyme was denatured at 90˚c and the next day it produced more bubbles at this temperature then there should have been at the optimum temperature. Although, the results were not that accurate the test was fair and safe and all the variables were kept constant. The same volume and concentration of hydrogen peroxide was used and the surface area of the potato was kept constant. The results that did not fit in with the main pattern were 40 that should have been a lot higher and 60, 70 and 90 which should have been a lot lower and not higher than the predicted optimum. My results are reliable enough to draw a conclusion, as there was a reasonable pattern even though it did not follow the Q10 factor. The line graph showed some sort of pattern however; it was not a very distinct pattern but you could see that at up to 45˚c the pattern rose slowly upwards but after it is not all a decrease and there is some increase especially 50˚c and 70˚c. I might have improved my method to obtain more evidence to support my conclusion by leaving the experiments for a longer time. This may have had an effect because if it was left for three minutes some temperatures may have stopped reacting at 2 minutes and 10 seconds while some may have gone all the way through to 3 minutes that may have made the graph and the results more accurate producing a more valid conclusion. If I also used more potato or a more or higher concentration of hydrogen peroxide I also may have got more accurate results. I think that I used more temperatures in between E.g. 15 and 25˚c there might have been more accurate results as I could see the exact difference that say 3˚c would make on the amount of bubbles produced.
Some better investigations that could be carried out to extend this investigation are if I measured the mass of gas lost, as digital equipment is used. Also if more electrical equipment were use human error would be eliminated.
By Daniel McIntosh