In my prediction I said that from 0°C every 10°C you go up to 40°C the temperature will double this is because as enzymes are heated they start to accelerate the rate of reaction (but they are more unstable). The reason for why the rate of reaction increases as the temperature increases is because in order to react, the particles in the substance must collide with each other. Heat gives them more energy to move around and so it increases the chance of reaction. This is what it looks like-
The molecules move faster so there is more
chance of collision.
= Hydrogen peroxide
= Catalase enzyme
As I said when the hydrogen peroxide is added to the enzyme catalase it starts to foam this is what it looks like.
But after the temperature of 40°C I have found out that the enzymes start to denature. This is because of the active sites of the enzyme- here is a diagram of what happens.
The substrate = hydrogen peroxide Products = water and oxygen
The active site can be described as a lock; the key is the substrate it has to break down. So when they are heated they are able to perform their task quicker but after 40°C the shape of the active site starts to change it’s shape this is known as denaturing it could be said that the lock is changing shape therefore the substrate will not be able to fit then eventually the reaction will not be able to take place so the rate of reaction will decrease.
The concentration of the enzyme will affect the rate of reaction because you have a fixed amount of active sites to perform the reaction. So if the enzymes are in a reaction it will not be able to go any faster until it has finished that reaction (then it can be used again) so it wont be able to go any faster unless you change different factors (these are temperature, PH and concentration of substrate).
I have also done some research to find out how this reaction happens and this is what I found that there is an Ion in the centre of the enzyme catalase molecule that helps to break down the bonds into water and oxygen molecules. This is what it looks like. (On the next page)
(I got my research from Encarta, Schoolwork and the Internet).
WHAT MEASUREMENTS DO YOU INTEND TO TAKE?
In this experiment the measurements I intend to take are-
For the 2ml of stock solution and 1ml of hydrogen peroxide I will use a measuring cylinder (ml). To measure the froth given of the reaction going up the test tube I will use a ruler but I will use mm because this is how accurate my ruler can measure to. The temperature of the stock solution will have to be taken to see if it has reached my wanted temperature to do this I will use a thermometer (measured in °C). I will have to use a measuring beaker to add 200ml of water to the stock solution. The temperatures I will use are 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C and 70°C. At each temperature I will I will repeat the experiment 7 times to get an average.
DESCRIBE YOUR PROCEDURE
APPARATUS
2 Measuring cylinders
4g of liver
2 Measuring beakers
8 Thermometers
49 Test tubes
8 Test tube racks
8 Water baths
Ruler
Hydrogen peroxide
Pestle and mortar
Funnel
200ml of water
DIAGRAM
METHOD
(Making the stock solution)
- Find a clear bench and take the pestle and mortar.
- Grind up the 4g of liver with the pestle and mortar.
- Measure 200ml of water with the measuring beaker and mix the ground liver.
- Once it is thoroughly mixed you will have to filter the solution.
- You are now left with the stock solution.
(Performing the experiment)
- Take 1 test tube rack and put 7 test tubes in it.
- Fill the test tubes with 2ml of stock solution using a measuring cylinder
-
Put the rack of test tubes into a water bath at the temperature of 0°C and put a thermometer in one of them.
-
By using the thermometer check if the temperature has reached 0°C.
- Have a suitable table to take down all of the results.
- Straight away measure 1ml of hydrogen peroxide with a measuring cylinder and add it to the first test tube quickly measure the froth going up the test tube.
- Do the same for the other 6 test tubes.
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Now repeat the experiment with 10°C, 20°C, 30°C, 40°C, 50°C, 60°C and 70°C.
HOW HAVE YOU MADE THE EXPERIMENT MORE ACCURATE
The way I will make my experiment more accurate is as follows.
Once I add the hydrogen peroxide into the stock solution I will take the reading from the top of the water level and the froths peak height. I will also be taking the temperature straight away so the stock solution doesn’t lose any heat (because in some parts of the experiment it will make the rate of reaction slow down). I performed an all or nothing experiment this proves that the enzymes are the reason for the reaction therefore we know why we are getting the results. When I was taking the temperature of the stock solution I was taking it at the bottom of the test tube for all the experiments I am doing this because of convection currents this is what they are.
From this diagram you see that the heat is changing throughout so if you take the temperature from the same place it makes it a fair test.
I will use the same equipment throughout to try and make it equal as possible. I used measuring cylinders and thermometers and used the most accurate measurement they can be used to so I can get the most accurate results I can get with my apparatus.
PRESENT YOUR RESULTS IN A SUITABLE FORM
CONTINOUS EXPERIMENT
ALL OR NOTHING EXPERIMENT
These results have been taken in mm because this is how accurate my ruler can measure to.
By looking through the results and the 1st graph I have found out quite a few errors. I have taken these results out and calculated the average again so these results will be more accurate. The results I have taken out is as follows for 0°C is 100mm (this is far to high) as well as that at 20°C I took out 80mm because this is far to low. Now my second graph will be more accurate.
EXPLAIN SIMPLY WHAT YOUR RESULTS SHOW
From my continuous experiment I have found out that as the temperature increases up to 40°C the rate of reaction increases. For example at 20°C the amount of froth released is 106mm whilst at 30°C the amount of froth released is 115mm this shows an increase of 11mm. But after 40°C the rate of reaction starts to decrease for example at 50°C the amount of froth released is 122mm whilst at 60°C the amount of froth released is 87mm this shows a decrease of 35mm this will be due to the denaturing of the active site.
The all or nothing experiment shows that the enzymes are the reason for the reaction. At 70°C the average amount of reaction is 1mm this shows almost no reaction this is because the active sites have denatured. At 40°C the rate of reaction is at it’s highest which is 139mm of froth released due to more collisions taking place.
The graph shows the rate of reaction increasing then decreasing which looks like a curve.
WHAT TREND, PATTERNS OR RELATIONSHIPS CAN YOU SEE IN YOUR RESULTS?
Firstly the continuous experiment shows that up to 40°C the rate of reaction increases but after 40°C the rate of reaction decreases.
Every 10°C up to 40°C I predicted that the rate of reaction would double but this is not the case in my experiment. From 0°C to 10°C the rate of reaction does double but I am not counting this because I have found out that the readings for 10°C are anomalous. Therefore the average amount of froth for the temperatures from 10°C to 20°C must be anomalous as well. The reason for why the amount of froth at 10°C is anomalous could be due to a few reasons and here they are
Firstly the first reason could be due to it is very hard to get the temperature so I probably didn’t get the right temperature. Another reason could be because when the test tubes were taken out of the water bath they could have been heated to room temperature which is about 25°C causing the rate of reaction to increase from what it should be.
I also have taken two results out the first one is at 0°C which is 100mm this reading is far to high the reason for this could be due to that the stock solution was not at the right temperature (it was too high that is why the rate of reaction increased to much) or the measurement of hydrogen peroxide I added could be too high. The second result I took out was at 20°C, which was 80mm, and this reading is far too low this could be due to the measurements I took were not right (not enough hydrogen peroxide was added) or the temperature may not have been right.
From 20°C to 30°C the amount of reaction does not double if it did the reading at 30°C should be a lot higher that it is which is 115mm. I also observed that the reaction did not take the same time but from the fastest to the slowest there is not much difference. At 40°C the amount of reaction is at it’s highest which is 139mm this is because of more collisions with the catalase enzyme and the hydrogen peroxide therefore more reactions take place meaning more froth released. But after 40°C the amount of reaction decreases because the active sites are being denatured (when the active site is disfigured the reaction cannot take place) by 70°C very very few or non of the active sites will be able to perform reactions.
The all or nothing experiment shows that the enzyme catalase has to be there for the reaction to take place you can tell this because of looking at the results that shows the amount of reaction at 70°C is 1mm whilst at 40°C the amount of reaction is 139mm.this shows a very big difference.
EXPLAIN YOUR RESULTS SCIENTIFICALLY AND RELATE THEM TO YOUR PREDICTION.
In the continuous experiment I predicted that every 10°C up to 40°C the amount of reaction should roughly double or you could say the rate of reaction doubles because it roughly takes the same time (this law is known as the Q10 theory). This is not the case in my experiment for example at 20°C the amount of reaction is 106mm whilst at 30°C the amount of reaction is 115mm this could be because the test tubes may not be long enough to hold all of the froth. Also all of the oxygen will not be given off as froth it may be given off in the gas form and if this is true I will not be able to measure it with my apparatus. The reason for why as the temperature increases the amount of reaction increases (up to 40°C) is because at higher temperatures the faster the molecules of hydrogen peroxide and catalase enzyme move therefore the faster they move the more chance of there to be a head on collision and when they collide they react so this shows why as the temperature increases the amount of reaction increases. This is what happens after 40°C you would think that if the temperature increases upwards the enzymes will be able to perform the reaction even quicker but this is not what happens; what happens is the active sites will start to denature because it is damaged this will mean the enzymes will not be able to react with the hydrogen peroxide. If you look at it like a lock and key (lock = catalase enzyme; key = hydrogen peroxide) if the lock is damaged the key will not be able to fit this shows how the reaction will not be able to take place. By 70°C the amount of reaction is 1mm I predicted that there would be no reaction at this point there is a very very small amount of reaction this could be because as soon as hydrogen peroxide is formed it decomposes naturally so oxygen is always being given off. Another reason is that not all of the enzymes could have been denatured because the heat may of not penetrated through every enzyme therefore allowing a small amount of reaction to take place.
The second graph and the average results shows as the temperature increases up to 40°C the rate of reaction increases and after 40°C the rate of reaction starts to decrease but the results will be more accurate because I have taken out the results which are not correct but it still does not agree to the Q10 theory.
I predicted that in the all or nothing experiment at 70°C there would be no reaction-taking place and at 40°C it would react the most out of all of the experiments and this is true. At 70°C there is a very small amount of reaction taking place this is due to the decomposition of hydrogen peroxide naturally or small amount of enzymes still being able to perform the reaction. Because the enzymes have denatured there is no reaction-taking place; if there are no enzymes there are no active sites for the reaction to take place so nothing happens. At 40°C the enzymes are working at its quickest speed that is why it has a higher amount of reaction compared to every other temperature.
I have come to the following statement from this experiment as the temperature increases the amount or reaction will increase up to 40°C but after 40°C the rate of reaction will decrease until around 70°C where the reaction will completely stop but there will always a small amount being released due to that hydrogen peroxide decomposes naturally. I will also say that the enzyme catalase is the reason for the reaction to take place.
COMMENT ON THE SAFETY OF THE PROCEDURE AND WEATHER IT WAS A FAIR TEST.
In this experiment it is hard to get accurate results (this is because it is a very crude experiment). Firstly I will talk about the temperature factor in the experiment; I have found this factor to be very hard to control. This is because when the temperature of the stock solution has reached my wanted temperature the test tubes will change so the reaction will be less or more.
It is not a fair test within the test tube because the heat of the test tube changes throughout it; the top of the test tube is hotter than the bottom this is what is happen and looks like- (on the next page)
This diagram shows how the temperature throughout will change due to convection currents.
The point up the test tube I will measure the froth from is the same for all of the test tubes but this is not fair because when the rate of reaction is higher more of the mixture is turned into froth (or oxygen) so the level I should measure it from should get lower as the rate of reaction increases.
But I have got out a set of results that roughly agrees to my prediction (as the temperature increases up to 40°C the amount of reaction will increase but after 40°C the rate of reaction will decrease). The concentration of the enzyme in this experiment is almost even throughout this is because I am using a stock solution (so this part is fair) the concentration will be the same because of diffusion (the definition of diffusion is the net movement of molecules that move from a high concentration to a low concentration until it is evenly spread out) in the stock solution what I mean is that the catalase enzyme will spread evenly throughout the mixture. The amounts will be quite accurate for the stock solution and the hydrogen peroxide. The measurement that will be least accurate is the hydrogen peroxide because as soon it is poured into a measuring cylinder the hydrogen peroxide will be decomposing naturally so it will decrease in volume.
HOW ACCURATE ARE YOUR RESULTS AND DID YOU GET ANOMALOUS RESULTS
I have repeated the experiment at each temperature 7 times this is done to get a more accurate average. But in these repetitions I have found some anomalous results; I have these results out the ones I have taken out are 100mm at 0°C (this result is far to high) and 80mm at 20°C (this is far too low) after taking these results out it has made my overall average of results more accurate these results could be anomalous due to the temperature may be wrong or the measurements I have taken with the hydrogen peroxide or catalase enzyme are not accurate.
The first problem I found out was trying to get the stock solution at my wanted temperatures this is because the water baths were not very accurate and it was difficult to get the temperature of the stock solution due to convection currents. When I take out the test tubes they will start to change temperature due to the different room temperature this will affect the rate of reaction.
The amount of froth was quite hard to measure because when the rate of reaction was high the froth would rise above the test tube. Also I measured the froth from the same place up the test tube and this was 3ml up the test tube. It was not very accurate (measuring the froth) because when the rate of reaction is high the more mixture is turned into froth (or oxygen) therefore the point where I should measure from should get lower as the rate of reaction increases.
This experiment is quite accurate because I said in my prediction that from 0°C to 40°C the amount of reaction would increase and this is what happens in my experiment; for 0°C the amount of reaction is 60mm and the amount of reaction for 40°C is 129mm this is correct because at 40°C the rate of reaction is at its highest with the enzymes. I also predicted that after 40°C the amount of reaction would decrease and this exactly happens in my experiment for example at 50°C the amount of reaction is 122mm so it shows it is starting to decrease and by 70°C the amount of reaction is 2mm this proves it is quite accurate. But my experiment does not agree to the Q10 theory that states every 10°C increase up to 40°C the rate of reaction will double and after 40°C the rate of reaction should decrease but my results do not double up to 40°C but it does decrease afterwards so it is not totally accurate.
These results are useful and are quite accurate put it is not very accurate because the apparatus is insufficient; but I am able to come to a firm conclusion from my experiment and this is the rate of reaction will increase up to and including 40°C but after the rate of reaction will decrease until 70°C where the enzymes are totally denatured.
HOW COULD THE EXPERIMENT BE MADE MORE ACCURATE?
Firstly I will give full details of the changes to make the experiment more accurate. I will use different apparatus to make the results more accurate. Here is a labelled diagram of what the experiment with the modifications.
Test tube
Rubber bung
Rubber piping
Water trough
Beehive jar
Gas jars
From doing this experiment with this apparatus I will be able to measure the amount of reaction far more accurately because none of the oxygen will be able to escape (it will all be measured).
Also I could repeat the experiment 10 times to get a more accurate average. Make the temperature of the stock solution vary more temperatures for example every 5°C up to 70°C this will give a better graph. When taking the temperature of the stock solutions keep on stirring it to get the same temperature throughout.
To do further work into investigating the break down of hydrogen peroxide with the catalase enzyme is to investigate different concentrations and see how it affects the rate of reaction.
I decided to perform a small investigation investigating this. Here is a small write up of the experiment.
I will be investigating the concentration of stock solution at two temperatures and they are 25°C (room temperature) and 40°C I will get these temperatures using water baths. For each temperature I will vary the concentration of catalase enzyme (the catalase enzyme concentrations will be 1, ½, ¼, 1/8, 1/16) I will also repeat this 3 times to get a more accurate average.
I predict that at 25°C as the concentration decreases the amount of reaction will be higher. I predict at 40°C that the amount of reaction will be higher than 25°C but the same thing will happen is as the concentration decreases the amount of reaction decreases.
What is happening in this experiment is as the concentration decreases there is less catalase enzyme to react with the hydrogen peroxide so the rate of reaction will decrease. You could say there are less active sites for the reaction to take place when the concentration decreases therefore when there are less active sites there will be less reactions taking place. At 40°C the molecules of hydrogen peroxide and catalase enzymes will be moving quicker so there is more chance of collisions so more reactions take place that is why the rate of reaction is higher even though it is at the same concentration. Here is a set of results from this experiment.
For 25°C
For 40°C
These results agree with my prediction for example in the experiment at 25°C the catalase enzyme at 1 has an average amount of froth released is 120mm whilst at 1/16 the average amount of froth is 23mm you can see it decreasing. At 40°C the catalase enzyme at 1 has an average amount of froth released is 143mm whilst at 1/16 the average amount froth released is 40mm this proves my prediction correct. This is because at the same concentration 40°C has larger reactions.
From this experiment I have learned that the concentration is a major factor in the amount of reaction that takes place but the temperature can increase reaction even further.
If I done more in this experiment I would expect to see a graph like this.
This graph shows – the first increase of reaction shows the concentration increasing then the vertical part shows when the concentration can’t increase the rate of reaction any further the second increase of reaction shows what happens when you increase the temperature then the second vertical part shows when the temperature can’t make the rate of reaction any further (the graph would start to go down if temperature goes over 40°C).
From this experiment I have came to a solid statement that if you increase the concentration you increase the rate of reaction.
