Catalase Investigation
Planning
In this investigation I intend to find out how surface area affects an enzyme catalysed reaction. To do this I will conduct an experiment using a potato (which contains the enzyme Catalase), Hydrogen Peroxide, water bath, test tube, bung + collecting tube and a measuring cylinder. I have chosen to use a potato as the catalyst for the reaction as it makes it easy to test surface area and it simulates the surface area much better than just a liquid enzyme. I have chosen the other pieces of equipment simply because they are what's available.
First of all I will fill the water bath up to about 3/4 of its capacity, this is because of the displacement that occurs when I put the measuring cylinder in and from a bad experience in the preliminary experiment I will not make the mistake of filling it up to the top again. I will then put 20ml of Hydrogen Peroxide into a test tube and cut the piece of potato using a special kind of cutter, which means I always get the same amount of potato cut. I will then fill up a measuring cylinder and place it upside down in the water bath and place the collector tube inside the cylinder. I will cut up the potato to the desired size and put it into the test tube, put the bung in the test tube and start the stopwatch. After 3 minutes I will take the collector tube out of the measuring cylinder and record where the water has gone down to in millilitres.
I will repeat this process 6 times for a complete set of results. If time allows then another set of results will be collected. The only thing that should change is the surface area of the potato; the volume of potato going into the test tube does not change.
2
Everything will be kept at room temperature and hopefully this temperature will remain constant. Obviously this is a variable that I cannot control.
My Prediction for this experiment is that the bigger the surface area the higher the result will be. This is because the more surface area you have the more enzyme is released from the potato causing the Hydrogen Peroxide to turn into Oxygen faster.
I will try to make the test as fair as possible, cutting the potato could be a problem as it is difficult to measure the cutting effectively, but it shouldn't make much of an impact on the results.
In an ideal world I would replace many of the apparatus after ...
This is a preview of the whole essay
My Prediction for this experiment is that the bigger the surface area the higher the result will be. This is because the more surface area you have the more enzyme is released from the potato causing the Hydrogen Peroxide to turn into Oxygen faster.
I will try to make the test as fair as possible, cutting the potato could be a problem as it is difficult to measure the cutting effectively, but it shouldn't make much of an impact on the results.
In an ideal world I would replace many of the apparatus after each result recorded, this is because washing test tubes etc makes the Hydrogen Peroxide more dilute when you add it to the wet test tube but I do not have the equipment to do this, but judging from the preliminary experiment the equipment doesn't seem to affect the results.
However every enzyme has a particular temperature and PH at which it works best. If an enzyme is subjected to extremes of PH or temperature, irreversible changes can occur in the structure of its active site. The enzyme becomes denatured and loses all its powers of catalysis. If this happens it will be obvious, as no oxygen will be produced.
In the preliminary work I conducted the experiment that I have described to see if it worked, the results were as follows:
Pieces Of Potato
Attempt
Amount Of Oxygen (ml)
Time (minutes)
6
3
2
2
0
3
4
3
8
3
The results are a little dubious but at least they are close together in terms of range. The results have helped me to improve the plan for the proper experiment, for example measuring how much Hydrogen Peroxide I put in the test tube, which I didn't do in the preliminary experiment.
3
Results
Set 1
Potato is 4cm long, temperature is at a constant 22°C, using 20ml of h²o².
Pieces Of Potato
Attempt
Amount Of Oxygen (ml)
Time (minutes)
8.5
3
2
2
9.5
3
4
3
1.5
3
8
4
8.5
3
6
5
23.5
3
32
6
25
3
Set 2
Pieces Of Potato
Attempt
Amount Of Oxygen (ml)
Time (minutes)
9
3
2
2
9.5
3
4
3
2.5
3
8
4
4.5
3
6
5
8.5
3
32
6
20
3
Analysis
Using the results from set one I have found out that the more surface area you have the more enzyme is released. This causes the Hydrogen Peroxide to produce more Oxygen as more pieces of the potato are added. From observation during the experiment it is also clear that the Hydrogen Peroxide produces Oxygen quicker as more enzyme is added.
My results prove that my prediction was right. I said that the more pieces of potato you put in (or the higher the surface area) the bigger the result will be. My results show that as you add more pieces of potato the amount of Oxygen also increases.
The results clearly show a steady increase in the amount of Oxygen being produced. In some places the amount of Oxygen increases significantly, for example from results three to four in set one, the amount of Oxygen increases much more than it does between any other result in the set.
4
The graphs show that the more pieces of potato you put in the test tube, the higher the amount of Oxygen. The increase starts off steady, rises dramatically and then levels off again, to create an s shape. I believe the reason it levels off as you put lots of pieces of potato in is that the Hydrogen Peroxide produces as much oxygen as it can in the amount of time given, and cannot go any faster even if you put more enzyme in. This is just a theory and I have nothing to prove it. Of course I could just forget the s shape altogether and use a line of best fit but then, the results would look out, because it is difficult to draw a line of best fit on points which are dotted about the graph.
Using the graphs I predict that if you keep adding more and more pieces of potato to the Hydrogen Peroxide then the graphs will level off completely or increase at a very low gradient.
Evaluation
I think that the first set of results were very accurate. The first experiment went well without any problems and I got no odd results. The graphs of the first set show a significant pattern which wouldn't be there if any of the results were odd. The experiment was also fair, I made sure everything was the same and I conducted each test in the same way every time. When reading the measurements I made sure they were to the nearest 0.5 of a millilitre. The first set of results, in my opinion, are very accurate and useful to task and purpose of the experiment.
However, set two is completely different. I do not believe that this set of repeat results is accurate. It does increase and follows the pattern of the set one graph but every result is much lower in value. There are a number of possibilities to why this happened.
It could be that the potato was subjected to extreme forms of temperature or PH, denaturing the enzyme. However if the enzyme was denatured then how are the results still quite high, if it was denatured then shouldn't the results be extremely low or the experiment not worked at all? A second possibility is that with all the washing of the equipment and the test tube, the Hydrogen Peroxide could have become dilute enough to the point where it affects the results. It could have been human error, I might have changed the way I conducted the experiment but I do not think I did this to the point where it would affect the results.
5
Another possibility is that there was a sudden change in the environment, but I checked the room temperature and it remained at a constant 22°C. It is in fact rather bizarre as to why I should get a table of odd results and I do not know the exact cause, but I think it is one of the possibilities listed above and most it is probably most likely that the Enzyme was denatured in some way.
I think my plan showed a sensible way of testing my prediction. It was quite a simple plan, and a simple experiment to conduct and more importantly it got good results. The most difficult part of the experiment was cutting the potato into equal amounts. I could not find a quick and effective way of measuring the cutting and had to go largely by guesswork.
I think my results do prove my prediction in a fairly solid way. Of course to back my prediction up completely I would need about 3 sets of results all showing near enough the same thing, but I did not have the time to do this. However, the pattern from the results is such that
To improve the experiment I would change the way I cut the potato to make it more accurate. I would possibly change the test tube that the Hydrogen Peroxide is kept in for each test to stop the Hydrogen Peroxide from diluting. To improve it further I would conduct it under a controlled temperature and a clean environment so the potato doesn't get contaminated.
By Jack Higgs 10K
