The Effect of Temperature On the Enzyme Catalase
THE EFFECT OF TEMPERATURE ON THE ENZYME CATALASE
PLAN
AIM
My input variable for this investigation is the temperature of the hydrogen peroxide solution. My output variable will be the rate of reaction of the enzyme catalase in the potato, i.e. the amount of oxygen given off. I will investigate how the rate of reaction of catalase varies as its temperature is varied. This will be shown by the amount of oxygen given off within a certain time.
PREDICTION
I predict that as you increase the temperature of the enzyme catalase the amount of oxygen given off will increase (i.e. the rate of reaction of catalase will increase). This is because catalase speeds up the chemical reaction H202 - - - -H20+02. Therefore, as you increase the temperature, catalase will gain more and more activation energy and so the speed of reaction will increase.
As the temperature of catalase is increased by 10?C I predict that the rate of reaction will roughly double, i.e. double the amount of O2 will be produced.
When a solution is heated, the particles move around quicker because they have more energy. Because they travel faster, they collide more often. At low temperatures, the particles do not always crash hard enough together to start a reaction. However, at higher temperatures, the particles crash much harder and therefore more reactions are started.
Above a certain temperature, I predict that the amount of oxygen given off will decrease rapidly and then eventually stop altogether. This temperature will be just over 40?C. At a temperature above 40?C, enzymes stop working as well and eventually at a temperature of around 50? - 60?C, stop working completely. This is because they become denatured. Catalase speeds up the reaction because it has special receptors with a certain shape on its surface. The hydrogen peroxide molecules are able to fit into them and then become broken. If the temperature gets to high then the shape of these receptors become deformed. Once deformed the hydrogen peroxide molecules can no longer fit into them and can therefore not be broken. Therefore, any oxygen given off at a very high temperature when the enzyme is denatured will be the natural breaking up of hydrogen peroxide. Not the cause of catalase!
A FAIR TEST
Other variables than temperature that could affect the outcome variable could be
I. The concentration of the enzyme.
II. The concentration and volume of the reactant.
III. The surface area, type and the mass of the potato.
IV. The method of collecting the oxygen given off.
In order to insure that my investigation is a fair test I will make sure that each of the above variables are constant each time I carry out the experiment.
METHOD AND SAFETY
Cut out a few pieces of potato using a 10mm cork borer. Using a knife and ruler to measure and cut these pieces into 12 smaller pieces, with a length of 30mm each.
Get twelve test tubes and two test ...
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III. The surface area, type and the mass of the potato.
IV. The method of collecting the oxygen given off.
In order to insure that my investigation is a fair test I will make sure that each of the above variables are constant each time I carry out the experiment.
METHOD AND SAFETY
Cut out a few pieces of potato using a 10mm cork borer. Using a knife and ruler to measure and cut these pieces into 12 smaller pieces, with a length of 30mm each.
Get twelve test tubes and two test tube racks to hold them. Use a syringe to fill up each tube with 25ml of hydrogen peroxide. Place a thermometer in each of them. Then put them in water baths that are set to temperatures of 30?, 40?, 50? and 60?C. For the temperature, 20?C use room temperature and for 10?C place in a beaker of ice.
Next go to one of the water baths and check it is at the temperature you want. Fill up a plastic bowl or a beaker with water. Fill a burette with water and connect it to a delivery tube. Then turn it upside down in to the bowl as shown in the diagram. Place one of your potatoes into one of the boiling tubes of hydrogen peroxide. Quickly put on a bung connecting it to the delivery tube and to the burette. Use a stop watch and after five minutes record how much oxygen has risen into the upside down burette. (This will be how far the water level has gone down during the five minutes). Do this twice for each temperature to get an average.
To make my experiment safe I will wear a lab coat and safety goggles throughout the experiment. I will be careful whilst using a knife or scalpel. I will also be very careful when handling hydrogen peroxide, as it is irritant and corrosive. After handling it, I will immediately wash my hands.
I will have my input variable, the temperature, at six different values. They are as follows: 10?, 20?, 30?, 40?, 50?, 60?C.
PRELIMINARY WORK
VALUES
Before doing the experiment, I did some preliminary work to try to find out what would be good values to use for the size of my potato, the amount of hydrogen peroxide and the different temperatures to use.
The other thing to consider is the amount of time I do each experiment. During tests, I found that at two or tree minutes, little amounts of oxygen were produced. Therefore, five minutes was enough time for reasonable amounts of oxygen to be given off.
For the size of my potato, I decided that a diameter of 10mm and a length of 30mm were perfect as the potato would be fully immersed and there would be enough of it to obtain adequate results.
I did some tests and decided that a good amount of hydrogen peroxide to use would be 25ml. This seemed the right amount, as it was enough to get sufficient results and did not let the froth rise to the top of the boiling tube.
The last thing to decide was the range of temperatures. Because I knew from my scientific knowledge that enzymes do not generally work above a temperature of 40-50?C I decided the highest temperature I would use was 60?C. I decided six temperatures would be enough. Since my quantitative prediction said the rate of reaction doubles every 10?C I though a difference in 10?C each time appropriate. Therefore, for 60?C, 50?C, 40?C and 30?C I used water baths. For 20?C I used room temperature and for 10?C I used ice to cool it down.
SOURCES OF INFORMATION
In order to make predictions and explain them in my plan I needed to learn more about enzymes and their properties. I used the following resources for information.
. Letts Study Guide GCSE
2. Key Science Biology
3. GCSE Double Science Biology- The Revision Guide.
4. My notes on enzymes made during my GCSE course.
OBSERVATION
Amount of O2 given off after five minutes. (1rst set of results)
Amount of O2 given off after five minutes. (2nd set of results)
Average amount of 02 given off after five minutes.
0?
.20
.10
.15
20?
.90
2.00
.95
30?
3.70
3.90
3.80
40?
4.00
4.20
4.10
50?
0.10
0.20
0.15
60?
0.00
0.10
0.05
ANALYSIS
After plotting my results on the graph opposite, I have found that as you increase the temperature the rate of reaction increases.
This relationship happens up to a certain point. Above a temperature of 40?C, the rate of reaction rapidly decreases and only a very little amount of O2 was produced at 50 or 60?C. This probably had nothing to do with the enzyme. It is likely, as it is such a small amount, that the O2 produced was the natural breaking up of hydrogen peroxide.
This relationship agrees with my prediction as the rate of reaction does increase as the temperature is increased. For example at 10?C, 1.15ml of oxygen were produced and at 20?C, 1.95ml of oxygen were produced. As I said in my prediction after a temperature of 40?C, the rate of reaction rapidly decreases. Looking at the graph, at a temperature of 40?C, 4.10ml of oxygen were produced but at 50?C, only 0.15ml of oxygen were produced.
This is because as you increase the temperature, catalase will gain more and more activation energy and so the speed of reaction will increase. As said in my prediction, this only happens up to a temperature of about 40?C. The reason for this is that enzymes generally work best just bellow 40?C because this is about the normal body temperatures of animals which they work in. Once the enzymes get too hot, their special receptors become deformed and so the hydrogen peroxide molecules can no longer fit into them. The enzymes therefore stop working and are now denatured.
The quantitative relationships for these results are as follows: as you raise the temperature by 10?C, the rate of reaction roughly doubles. This agrees with the quantitative prediction I made, as the rate of reaction does roughly double as the temperature is increased by 10?C. For example looking on my graph at 20?C, 1.9ml of oxygen were produced and at 30?C, 3.8ml of oxygen were produced.
This is because when it is heated the particles move around quicker because they have more energy. Because they travel faster, they collide more often. At low temperatures, the particles do not always crash hard enough together to start a reaction. However, at higher temperatures, the particles crash much harder and therefore more reactions are started.
EVALUATION
The results I got were fairly accurate. In the two times I did the experiment, the results I got were close enough together to say this. For example at a temperature of 10?C, 1.10ml of oxygen were produced the first time, and 1.20ml produced the second time. At a temperature of 20?C, 1.90ml of oxygen were produced and the second time 2.00ml of oxygen were produced. As you can see the amount of O2 produced each time were not out by much so I can therefore say they are accurate. Another reason I believe my results to be accurate is that I was very careful when measuring amounts of hydrogen peroxide, when measuring the size of the potato and when checking the temperature of the hydrogen peroxide solution.
I feel that there were no inaccuracies in my results. However, I do believe that if I repeated the experiment there are things I could do to improve my experiment. The main thing I could have improved is how I measured the amount of oxygen produced. Instead of just measuring the amount of oxygen given off after five minutes, a better idea would be to record amounts given off each minute. This way I would have more results to plot and therefore have a much more accurate graph. I could also have counted the no. of bubbles produced each minute. This would have given me another set of results and I could have gotten more evidence towards my conclusions.
None of my results appear to be anomalous.
My results are good enough to support the simple conclusion that as you raise the temperature the rate of reaction increases up to a temperature of 40?C. As the graph clearly shows, as the temperature steadily increases the rate of reaction increases. Once the temperature passes 40?C the graph goes rapidly down near the zero mark, meaning little or no reaction is happening.
My results are good enough to support my quantitative conclusion that as the temperature is raised by 10?C the rate of reaction roughly doubles. For example looking on my graph at 20?C, 1.9ml of oxygen were produced and at 30?C, 3.8ml of oxygen were produced. Although the rate of reaction does not always double exactly, it is what roughly happens. I believe however that if I had had more time to further extend my investigation I would have a lot more proof for this conclusion.
If I had more time, there are several things I would do to get more evidence to support my conclusions. I would repeat the experiment twice more so I could get a better average of results and also find the rate of reaction at 0?C. I would do what I said I could have done to improve my experiment, which is to check the oxygen level each minute and also count the number of bubbles produced each minute in the next two sets of results I get. I would plot the number of bubbles produced on to a graph and write more conclusions about them. This would provide me with much more evidence than I currently have.
To extend this investigation I could try finding the amount of oxygen given off when yeast is put in hydrogen peroxide and heated to various temperatures. I could also possibly use a wider range of temperatures, maybe every 5 degrees instead of ten. Therefore, I would use the temperatures 10?, 15?, 12?, 25?, 30?, 35?, 40?, 45?, 50?, 55? and 60?C. Another possibility is to test out the rate of reaction of different enzymes for example amylase. I could then compare how the rates of reactions when varying the temperature differ in the two enzymes.
Lindsay Fletcher 11DMH