There is a depression on the surface of the enzyme called an active site, the substrate molecule needs to hit this molecule at the right angle to fit into the depression. It's like a key fitting into a lock. ( In this experiment the lock is the catalase enzyme and the key is hydrogen peroxide.) Then the substrate and enzyme form a reaction, and then the substrate when broken up into the products is released so the process can happen again.
So when the enzyme concentration of potato is increased then the chance of a substrate molecule hitting a enzyme molecule at the right angle is, also increased.
Baced on my predictions I think that the graph of results will go up quite steady with the time on the x axis and the volume of gas produced on the y axis. The lines will be labelled with how many pieces of potato.
preliminary work
As preliminary work for the investigation, i have performed a number of tests to determine conditions for geting the best results. The first experiment used a 1cm piece of potato,
firstly cut by a size 4 cork borer, the potatoe contains the catalase. I then used different amont of hydrogen peroxide, but settled on 18ml, we also put in some washing up liquid in the hydrogen peroxide because we found that when the oxygen bubbles form the burst before we could read the accurately. We then decided on a time of when we could measure the oxygen bubbles that had formed, in the firsted experiment that we tried we left a gap of three mins but then we changed it to 1 min because the experemnt took to long.
So from the preliminary work we concluded that 18ml of hydrogen peroxide and a size 4 cork borer for the potato which would then be cut into 1cm pieces using a 50ml measuring cylinder to collect the gas in.
In this investigation, so that I get accurate results I am going to do the experiment four times this will include: doing the experiment with seven diffent amounts of bits of potatoe they will be 2 pieces of potato, 3 pieces, 5 pieces, 6 pieces, 8 pieces, 10 pieces and then 12 pieces of potato, I will then measure the volume of gas prodused evey minuite for eight minuites.
Apparatus
- measuring cylinder
- potato
- size 4 cork borer
- knife
- ruler
- hydrogen peroxide
- washing up liquid
- maker pewn stop clock
Diagram
methord
-
I will Set up all the equipment: put the 18ml of hydrogen peroxide and the 2ml of washing up liquid into the measuring a cylinder.
- I will Put the cork borer though the potato, I then push the potato back out again, then I wil lay the piece of potato down against the ruler and cut it into smaller bits of 1cm.
- I will drop the potato into the solution, in the measuring cylinder, I will then started the stop clock, every minuite I will check how much (o2) has been produced. I will then mark on the measuring cyilinder how high it was, so that its easier to measure next time. But I wont stop the clock. I will do this for eight minuites.
- I will do the experiment seven times using different amounts of potato each time: 3, 5, 6, 8, 10, 12 pieces.
- The will repeat the whole experiment (stages1-4) again four times.
SAFETY: In my experiment I need to be alert at all times, when using hydrogen peroxide (H2O2) I need to:
1. Wear safety glasses.
2. Stand up at all times.
3. Keep bags and stools under desk.
4. Wipe up any spillages.
5. Follow the lab safety rules.
6. tie long hair back
7. avoid contact with chemicals
Results tables
First experiment
Second experiment
Third experiment
Fourth experiment
To find the average of all the results I added each result to gether then divided by 4. example:
2 pieces of potato at 1 minuite = 2+1+3+4=10 10/4=2.5
averages
Rounded averages
Graph
Series 1 = 2 pieces of potato
Series 2 =3 pieces of potato
Series 3 = 5 pieces of potato
Series 4 = 6 pieces of potato
Series 5 = 8 pieces of potato
Series 6 = 10 pieces of potato
Series 7 = 12 pieces of potato
Conclution
These results show me that increasing the amount catalase (potato) in the reacton the more oxygen is produced. we can see this because if you look at the 1 minite colum on one of the tables, the more potato that is in the solution the higher it is ussaly:
The trend shows that as the amount of catalase goes up the gas produced goes up. The reason that the amount of gas produced goes up is because the total surface area of catalase is increasing and this would mean that there is more chance of the hydrogen peroxide colliding with it.
I think the results on the graph level of at the end beacuae the supply of hydrogen peroxide when there was two potato pieces was, 9ml of H2O2 per potato piece, and when there was five pieces it was, 0.27ml of H2O2 per pices of potato. This is showing that there was a lower concentration of H2O2 in the experiments with more potato. Because there was a lower concentration of H2O2 that would have made their be less chance of particles hitting into a certain bit of catalase therefore not giving it the same chance as a bit of catalase in an experiment with less catalase. Because of there being less H2O2, in experiments with more potato suggests that the H2O2 was running out towards the end of the experiments and therefore the catalase might not have been working to its full potential in the experiments with more potato. Also as the H2O2 was being broken down water was being produced which was lowering the concentration of H2O2 towards the end of the experiments.
The trend doesnot go up in a set amount because if I look these results and take 3 pieces of potato, we can see that the amount of o2 produced was 4ml so if we double thiswe would expect it to double:
Pieces of potato = 3p o2 produced =4ml
X2
Pieces of potato = 6p o2 produced =8ml
But as we can see in the table below that isn’t the case, it doesn’t follow this pattern.
My results agree with the pridiction that I made apart from the part I have just explain the results not following a pattern.
Evaluating
In this experiment I have tried to be as accurate as I can, but this was difficult to do because it wasn’t always clear which point the o2 level was at, but it was as accurate as it could have been,the lack of accuracy is shown in the results where some of the results stay the same for a long period of time, this would have been because there was such a small change that I couldn’t really see or record it.
In the graph most of the results were accurate but there are a few anomalous points (they are circed on my graph). This couldn’t have been caused by the concentration of the H2O2 could not have been the problem here because all the other results that used the H2O2 from the same bottle were roughly on target.
It could have been caused by a change in temperature but this is unlikely because most of the other results that were recorded at the same time fitted in with the trend. Probably the thing that caused this result to be anomalous was that there may have been an abnormal bit of potato.
As I explained in the concultion the ratio of H2O2 and potato was different in each experiment because the same amount of H2O2 was used in each experiment. Therefore the supply of the H2O2 may have started to run out towards the end of the experiments with more potato and cause the results to change. What could be done to prevent this would be putting the same ratio of H2O2 to potato in each experiment or putting the pieces of potato in a larger solution of H2O2 so that the supply does not run out. One other problem that might have affected the experiments was that the pieces of potato might have been touching each other and blocking each other's access to H2O2.
