From the list above, I have decided to use the temperature of the reaction as my variable, using a specific range to find its optimum temperature. I will be using time as my control, timing each experiment for 1 minute.
Apparatus
- 33 pieces of liver
- Gas Syringe
- Rubber Bung with Syringe Needle
- 330ml of 0.2M Hydrogen Peroxide
- Timer
-
100cm3 Gas Syringe
- Retort Stand
- Boss
- Clamp
- Bunsen Burner
-
500cm3 Beaker
-
500cm3 Conical Flask
- Top Pan Balance
- Scalpel
Method
- Collect apparatus and set up as above
- Heat the water to required temperature. Record the exact temperature before starting the experiment
- Weigh a piece of liver by cutting it into a suitable size and place onto the Top Pan balance. Place it into a conical flask
- Put 10ml of Hydrogen Peroxide into a syringe
- Place syringe into rubber bung and start the timer as soon as the H2O2 is first poured in
- Wait for 1 minute and record the amount of oxygen that has been produced by the liver using the gas syringe
- Complete the experiment for the remaining temperatures and then go back to step 2 for repeats
The temperatures that I will be using are:
- 10ºC
- 15ºC
- 20ºC
- 25ºC
- 30ºC
- 35ºC
- 40ºC
- 45ºC
- 50ºC
- 55ºC
- 60ºC
Preliminary Study
My preliminary study was to investigate the effect of Hydrogen Peroxide on potato chips. Using Focus Software on the laptop computers, I used 5 potato chips at 5 different temperatures. I measured the amount of oxygen produced after 1 minute and repeated the experiment 3 times. Here are my results:
Calculating Rate of Reaction
Rate of Reaction = Average O2 produced / 60 seconds (*100 if plotting a graph to get easier figures)
The first graph shows the amount of oxygen produced against the temperature of the reaction. It shows that the enzymes inside potatoes have an optimum temperature of about 38°C. The second graph shows the rate of reaction against the temperature. It shows that the reaction is faster when the temperature is between 30 and 40 degrees.
Fair Test
In my experiment I will be doing a number of things to get as accurate results as is humanly possible. Firstly, I will use a syringe to get accurate measures of Hydrogen Peroxide. Also, I will be measuring results to 2 decimal places, and some to 3 decimal places.
Prediction
I think that as the temperature of the reaction is increased, then the amount of oxygen released from the liver will also increase. This is because an enzyme would work a lot better under a specific temperature, which I will be finding out. If the temperature is raised to far, then the enzyme will denature and so the piece of liver will not produce as much oxygen. This will also reshape the key, which will then not be able to fit into the lock.
Analysis
The results that I have collected show me that when an enzyme is heated to a specific temperature, it produces more oxygen than at another temperature.
Using my first graph, I can say that in this case, the piece of liver produced about 22.5mm3 of oxygen at 35°C and at 50°C it only produced about 5mm3 of oxygen. From my first graph I can see that the enzymes optimum temperature is 22.5°C. After this point, it denatures, and before this point, the enzyme is not working as well as what it could be. My results from this graph are quite accurate and there does not appear to be any anomalous results. As you can see, I stopped recording results at 60°C. This proves to be a very good point to stop as the enzyme looks as if it is producing very little oxygen.
My second graph shows the rate of the reaction and is more or less the same shape as my first graph. This graph shows that the enzymes was reacting its best at about 37°C, and that after this point, the enzyme denatured. This is what my first graph also shows.
This graph is also very accurate, as there appears to be no anomalous results.
Using both graphs, I can say that the piece of liver has to be at about 37°C to react at its full potential (3.75), and produce the highest amount of oxygen (22.5mm3).
The two graphs that I have produced are very similar to the graphs from my preliminary work. This tells me that all enzymes have very similar conditions and work in a very similar way.
I think that the reason for the increase in enzyme activity at the start of the reaction would be because there are a lot of collisions happening at this time. This activation energy is what gets the reaction started, but when the amount of oxygen produced reaches the optimum point, then the activity starts to decline. This is because the enzyme has denatured so the active site ‘lock’ has changed.
From my experiment I can now say that as the temperature of an enzyme increases, the amount of oxygen produced by the enzyme also increases, but only up to a certain point. At this point, the amount of oxygen that is produced starts to decrease and very little oxygen is produced.
Also, the rate of reaction proves this and the graphs all look very similar. The point at which the amount of oxygen produced starts to decrease, is where the enzyme works at its full potential. This point is very important to so that we know what conditions are ideal for certain enzymes.
I have found that once the temperature is past 37°C, then the key will no longer fit into the lock and the reaction can no longer occur.
This happens in the human body as well, i.e. most of our enzymes have an optimum temperature of about 37.5ºC. This is because all of the enzymes work more efficiently at this temperature, so it would make sense for them to have this temperature as there main conditions.
Evaluation
If I were to do this experiment again, I would change a number of things to my procedure so that I could get more accurate results. This changes would be:
- To use a water bath. This is a bath that heats water to a specific temperature and keeps it there. This would then make my results far more accurate, because when using a Bunsen burner, the temperature still rises even after taking the flame away from the reaction. It can rise by about 1, 2 or even 3°C.
- To use a digital thermometer. This would give me temperatures correct to 2 decimal place. This would lead to more accurate results and make things a lot easier.
- To keep the mass of each piece of liver the same so that the results that I obtained would be very similar, and 100% dependant on the temperature. If the pieces were all different weights, then one piece could produce more oxygen than another.
I think that the suitability of my procedure was good, as I find out what I wanted to find out. I think that if I had done the same experiment but with potato chips and then compared the two, I would have been able to come up with a better conclusion than what I have concluded so far. This is because liver has more catalase than a potato chip, but it is easier to measure potato chips, so I could have used the surface area of the chip as well.
I was quite pleased to how my experiment worked out and I think that my results were quite accurate. I did find a few anomalous results, these were:
-
Experiment 1, where the temperature was 29ºC and the mass of the liver was 0.60g and the amount of oxygen produced was 17.0cm3. I would have expected this result to have been at about 15ºC or less, so that the jump would not have been as much to the next result (22.8cm3)
- Experiment 1, where the temperature was 44ºC and the mass of the liver was 1.51g and the amount of oxygen produced was 13.6cm3. I would have expected this result to be about 16 or a little higher. The results following this should also have been a lot higher as well.
Looking at my preliminary results, I would say that there was not that much of a change in the graph shape. I would also say that the temperatures and the results from my preliminary study were roughly the same (the proportion, not figures). That is to say that at the optimum temperature was roughly the same and the enzyme begins its activity at the same point (roughly).
My aim, ‘to investigate the effect of Hydrogen Peroxide on a Catalase enzyme, whilst heating the reaction at different temperatures’ has been reached. I have done this by using Hydrogen Peroxide and pieces of liver, and I have done it at a number of temperatures.
I think that the suit
I can also say that I was right with my prediction, as I said that I thought that if the temperature of the reaction were increased, then the amount of oxygen released from the liver would also increase. This has proved to be true. I also said that this would be because an enzyme works a lot better under a specific temperatue, which I found out to be 37°C. I then said that if the temperature was raised to far, then the enzyme will denature and so the piece of liver will not produce as much oxygen. This is also correct, as I have found out using different temperatures to measure the amount of oxygen produced. I lastly said that if the temperature were raised above an enzymes optimum temperature then the key would be reshaped and therefore would not be able to fit into the lock.
