I must also try to get the temperature as accurate as possible. I will be doing all this by controlling the factors.
As the only variable we are changing is the temperature it is important that when we wash out the conical flask we will wash with cold water as warm water could help change the temperature of the hydrogen peroxide. It is also important that the water is preferably around room temperature and not too cold otherwise this could cool the hotter temperatures of the hydrogen peroxide quicker prior to doing the result taking.
If the celery is sliced then this would mean unfair results as the surface area could change for the different experiments, we could keep the surface area very similar by processing it until it is a mush, as a larger surface area would make the reaction quicker. Also this would be a good method as catalyse is contained in the middle of the celery and may never come into the reaction if in chunks.
If we measure the celery into the measuring cylinder then a lot would get stuck to the side and then when entering it into the conical flask some mass of the celery would be lost. To avoid this and to keep the weight of the celery as near 5g as possible the conical flask will be placed onto the scales, then the celery will be measured into it, using a spatula to guide the celery in to prevent it sticking to the sides.
To make my results as accurate I will be doing 2 sets of results, and then find the mean of the results. This will also spot any anomalous results.
I will take my results from between 16°C to 70°C. Starting at 16°C as this is the lowest at which we can get the hydrogen peroxide during the given time.
We will take the results often, taking them more often around 40°C as this is when it will work at its best. We know this as the human body stays at 37°C as the enzymes work at its best around this temperature. We also know that at a smaller temperature the particles will have very little energy and if it did collide with the enzyme it may not have the energy to succeed the reaction. I will also take results more often from 50-70°C, as this is when the temperature will denature, as it can only reach an optimum point.
Reliable Results
To avoid anomalous results and so spot them easily I will be taking 2 sets of results of the hydrogen peroxide at each temperature. This will enable me to make sure that the first set of results gained is close to the second set of results. We will then get the average of each temperature. Doing this method of taking more than one set of results should ensure that the results are reliable, as if one of the results is no where near the second set we know that something had gone wrong.
Also the hot plate will be monitored and as soon as it has reached its desired temperature we will work quickly at obtaining the result, having as much equipment set up as possible to try to ensure the temperature stays at this temperature. Whilst the hydrogen peroxide is on the hot plate it must be monitored closely to avoid over-heating.
Also to make sure we have reliable results, the variables will be kept the same apart from the temperature. The equipment will be cleaned to affect contamination from previous substances.
Information Gained
We had two lessons before the experiments to gain background information. Such as the ‘lock and key mechanism.’ Information like this had to be gained so that it was possible to find a way to gain results during lesson time. The ‘lock and key mechanism’ is when the enzyme (celery) and its substrate (hydrogen peroxide) meet. The substrate is the substance on which the enzyme does its work. The substrate and the enzyme must fit together in the way that a lock and its key fit together. On the surface of the enzyme, the substrate is changed to some other compound (in this case Oxygen.) The new compound separates from the enzyme. And so the enzyme is again free to combine with another molecule of the substrate. This can happen again and again. Such information like this was available through text books called “Hunt and Sykes” We also looked into the body and at the temperature at which the enzymes work. The body temperature being 37°C.
Predictions and Reasons
Through information gained in lessons and background knowledge I predict that as the temperature of the hydrogen peroxide increases so will the amount of oxygen produced, and should work at its best at around 37°C, as this is the temperature at which the enzymes in our body work at. Also at the point of reaching around 45°C I predict that the amount of oxygen produced should decrease. Reason being that enzymes are proteins and their structure is three-dimensional. Increasing the temperature disturbs the intra molecular bonds that hold the 3D shape. Because of this the shape is altered. Enzymes have an active site. This fits into the substrate molecular. If the active site is altered the substrate will no longer fit in and so the enzyme doesn´t work properly.
The rise of reaction rate is also due to the increase in temperature, relating to the kinetic theory. The higher the temperature, the faster they move. This happens but only to an optimum of 40ºC. The curve leading up to the optimum point is gradual but as it is reached it falls dramatically. The reason being that the active site is destroyed therefore no reaction can take place as there is only one specific active site per substrate.
Results Table
From observing the results table I can see that as predicted the amount of oxygen produced increased as the temperature increased as it took less time for the 10ml of oxygen to be produced. Also as predicted the production of the oxygen started to denature around 45°C. I shall now display my results in a graph.
The trend in the graph supports my prediction as it shows that as the temperature of the hydrogen peroxide was increased, the amount of oxygen also increased. However to show this positive correlation clearly, i.e. a graph looking like so:
I shall do a rate compared to temperature graph. The calculations for the rate will be multiplied by 1000 in order to make it suitable numbers to display on a graph.
Calculations
These results now display the positive correlation as the temperature increases so does the rate of reaction.
These shall now be converted into a graph.
Analysing Results and Conclusion
The shape of the 2nd graph shows my predictions well as it shows all the stages at which were intended, like so:
From my results it appears that catalase works best at 40ºC, and it has denatured at 70°C. And by observing the initial part of the reaction it is clear that the gradient is steeper between 0-16°C.
Looking at my background knowledge and prior experiments using enzymes I can explain my results as follows.
Kinetic theory states that particles, which gain heat energy, move more quickly. In our case the reacting particles are the substrate (hydrogen peroxide) and the enzyme catalyse. As the temperature is increased the particles of hydrogen peroxide have more energy therefore they collide with the celery more frequently and so increasing the rate at which the product is formed. However at a certain temperature this is no longer the case. This is because enzymes are proteins and proteins can be denatured at high temperatures. This is because proteins have a 3D shape. In our case the catalyse has a certain shape that the substrate fits into. At high temperatures the active site on the enzyme is altered. This stops the substrate from ‘fitting´ and so no product is formed.
My results support my original prediction at which the temperature that would have the greatest production would be around 37°C, the graph also shows the denaturing from 45°C onwards as predicted.
Whether or not my prediction was undermined about the optimum point being 37°C could have been proven more clearly if I had of actually done the temperature 37°C instead of 35 and 40.
Evaluation
In my investigation I was pleased with my achievements.
In my method, keeping the temperature constant throughout the investigation was hard to maintain, as the temperature of the contents of the tube would change quite quickly and therefore the hydrogen peroxide wouldn´t be at the temperature required. To overcome this problem I could keep the test tubes in a hot water bath for all the temperatures making sure that the water bath was the suitable depth. This would ensure constant temperature throughout the time taken to obtain 10ml of oxygen.
Also another problem that I observed on accuracy was that I didn´t allow the temperature to equilibrate to the right temperature. In this case I wasn´t using the correct temperature that I wanted, this could have led to some anomalous results. Ideally I should have brought the temperature of the hydrogen peroxide up to the needed temperature before adding to the celery.
Looking back at my results I found some anomalous results in my findings. When averaging I used these results, which could of made the average either lower or higher than it should be. To improve this I should have missed these results. Not including some sets of results when making averages may have led to better values.
My results are in line with those I predicted. Graphs indicate rise in temperature up a point leads to an increase in oxygen production. This is in line with kinetic theory. However it is very clear that after a certain temperature is reached the enzyme actually virtually stops. This supports my theory of lock and key fit.
However optimum activity of enzyme is at about 37ºC this is as we expected. This could have been proved more clearly if I had used the temperature of 37°C in my results. But at 65ºC the enzyme is still not denatured according to my results. This is a higher temperature than I would expect. Possible not allowing solutions to reach temperatures selected has led to an inaccuracy. It may be that in fact that many temperatures of solutions were lower than we stated.
Overall, due to reliable repeats and in general predictions being confirmed I feel my results are reliable enough to make a conclusion.
The obvious thing I would improve about the measurements I made would be to take more frequent temperatures around 65°C and 35°C temperatures to find a more accurate optimum and denatured temperatures. However I would have had to find a reliable way at keeping the temperatures as stated.
