- Spillages must immediately be cleaned up in the case of slipping on it or touching it mistakenly.
- Hair should be pulled back to avoid chances of having it dipped in chemical substances. It can also interfere with chemical reactions.
- When the experiment is complete and equipment and spillages are taken care of, hands must be washed thoroughly.
The Preliminary Experiment:
I tried to test the outcome of the enzymes present in peeled potato and unpeeled potato at different percentages.
With this test, I had experimented with various percentages of catalase, but had preferred to stay with 60%, as the experiment wasn’t too fast or too slow. At this medium speed, I could then observe the results more easily, thus; record my findings with more understanding of how the experiment progresses.
With these results, I found that there was a difference of 7.1cm3 (between 49cm3 and 42.2cm3) first but as it continued, there was eventually a difference of 0.8cm3 (between 29.3cm3 and 28.5cm3). This means that there are fewer enzymes available for the making of the enzyme-substrate complex. However; it could also mean that the substrates are almost engulfed completely so the reaction is slowing down.
From this preliminary experiment I could calculate the volume of oxygen produced and with that I could tell if that the percentage of catalase is effective. This would then tell me which of the percentages would be best appropriate for my actual experiment. In addition; after comparing the differenced between the peeled and unpeeled potato, I can then choose, which I would then use for my actual experiment.
When compared with my prediction, I can see that I was correct when stating that when more catalase is added, the rate of reaction increases. I can identify this on my table as my results changed dramatically every two minutes.
I can also tell that the unpeeled potato is much faster than the peeled. This can been seen on my table, as the peeled potato can only function with its enzymes when there is a 100% catalase concentration.
From my preliminary, I’ve decided that the unpeeled potato is more effective to use in the actual experiment. Additionally; I also chose to compare different amounts of catalase again.
Results:
Unpeeled Potato
Peeled Potato
Fair Testing/ Accuracy and Precision:
Before beginning the experiment make sure that all data is measured in specific units as to limit the chances of confusion or the recording of imprecise data. This means that one would need to measure (using cylinders and burettes, etc.) using cm3 as it is more reliable. This will assist in achieving accurate results at the end, which are vital when receiving a lot of data.
All variable that should remain constant should not be changed for this experiment. The hydrogen peroxide must stay at 5ml, otherwise; the experiment would have faulty results. In addition; before starting the experiment it is best to calculate all figures and measurements of the desired amount of water and catalase. It is important that the percentage of catalase counteracts the percentage of water to achieve fair results.
The washing of equipment and using when they are dry can increase the accuracy in the final results. This is because the excess water or solution that remains in the conical flask or measuring cylinder can add to the reaction that was supposed to take place. This could affect the experiment in such a way that predicted results would seem out of place. As well as this, the addition of the solution or water might aggravate the reaction and make it more active and dangerous (if the person using the equipment does not know of the last chemical that was put into the flask). Due to this, it is most advisable to make sure that equipment used is clean and dry before beginning the experiment. Therefore, a more fair and valid reaction can take place and with it data is correct.
This is also considered when using the same equipment twice – data can be corrupted and imprecise. This is due to the fact that only the first test would be correct while the rest would false as other reactions where experimented with equipment that still contain the chemicals used from the first experiment. As the experiment progress (and as more chemicals are used); by using the same container chemicals would build up in them. Therefore; results might then seem observed.
A factor to consider during the experiment is the ways in which the reaction unfolds and takes place. For example; during the experiment I noticed that bubbles would become wedged in between the delivery tube and the burette. However; if somehow the conical flask is shaken accidentally, the bubble would become free to float at the top of the burette. Therefore, the rate of reaction is then influenced. I also noticed that he slower the bubbles are formed, the slower the rate of reaction. Nevertheless; it is best to leave the bubbles wedged in as after a couple of seconds later, the bubble is then released and the reaction can continue straight after.
Linking with this problem is the shaking of the conical flask while the reaction is in progress. When all the contents in the experiment are put together, already that starts the reaction, but when the contents are then mixed (shaken) vigorously the reaction is speeded up by allowing more collisions to occur. This links to my hypothesis in stating that the when the concentration of catalase is increased, the rate of reaction increases also. However; this can be changed if the conical flask is shaken throughout the experiment – further influencing the rate.
If the lid attached to the conical flask (and further attached to the burette) is not big enough it will allow the reaction’s product to escape, therefore; there will be no results to record. If the reaction is continued while the oxygen is released, the rate of reaction would seem low. Nevertheless; as not all of the oxygen particles are collected, it would mean that the reaction is not fairly progressing. Therefore; this is an imprecise experiment.
It is important to activate the stop watch as soon as the reaction begins. This is the time when the hydrogen peroxide is added along with the dilution factor of catalase. As soon as this occurs it is best if another person presses the stop watch quickly while you close the top of the conical flask. However; some reactions will not begin until the contents are shaken to begin initiation.
When recording measurements from the burette, it is better to make surety that the measurement was lined exactly under the meniscus. If the whole experiment followed this one rule; the results (on a graph) would look irregular and would share a pattern with the other reactions using different concentrations of catalase.
When watching the experiment alter during the reaction stage, one can forget to watch the stop watch, therefore; data can be inaccurate. Also; if a couple of seconds pass the time limit, measurements can be changed in such a way that it may seem odd if when written next to the other results.
Another factor affecting the use of a stop watch is the questioning if the watch actually works properly. By avoiding finding the answer when it’s too later (during the reactions), it is best to check if the stop watch works before attempting the actual experiment.
It is best if the test is repeated more than once so that the results can be made into an average amount. That way, the results can then be plotted into a precise graph.
Equipment:
Chemicals:
Controlling the Experiment:
For this experiment, various necessities have to be controlled so that the experiment runs accordingly. Results have to be written fairly, so variables need to be controlled in order to maintain this.
Method:
I have used the same method from the preliminary as it best suited my working out. However; in addition have also repeated the experiment for fair testing and to get the best average results possible in this reaction.
- Dice an unpeeled potato, into small slices (the bigger the surface area, the better), then put into a blender to liquefy.
- Pour into beaker to then divide into four test tubes.
- Place test tubes into centrifuge and wait till the unpeeled potato has separated into a thick layer (top layer) and a more liquid layer (bottom layer).
- Place test tubes in a safe place as you will come back to use it.
- Fill a small bath tub with water, mid-length.
-
Fill a burette with water – preferably near the 50cm3. Then place a stand over the tub, this will hold the burette into place during the whole experiment, so make sure it is straight so that reading the measurements constantly is accurate.
- Insert a delivery tube up the burette; this must be connected to a stopper.
-
Using a pipette, extract the liquid from the bottom of the tube and place into a measuring cylinder to determine a percentage of the catalase that you want to test (measurements must be up to 10cm3).
- Pour distilled water in the left over percentage to dilute the catalase. Pour the contents of the measuring cylinder into a conical flask. I will test 20%, 30%, 40%, 50%, 60% and 70% of catalase in these reactions.
- (Have a stopper attached to the delivery tub in hand and be ready to press the stop watch) pour 5ml of the hydrogen peroxide into the conical flask and straight away close the top with the stopper.
- Immediately activate the stop watch.
Finally…
- Every 2mins (confirming with your stop watch) record where the meniscus on the burette stopped at. Keep track of the minutes.
- When experiment is completed, try another percentage and so on.
- Later using the formula (Initial reading – The Reading After 2/3/4, etc. minutes) to find the oxygen level.
- You may wish to display your data in a graph.
Results:
Table: Showing Average Reading and Volume of Oxygen Produced Per Catalase Percentage
Analysis:
The graph illustrates and further emphasises that as the concentration of the catalase is decreased the water amount would increase. Due to this theory, as a higher percentage of catalase is used (60%, 70%, 80%, etc.), the rate of given reaction would increase. Therefore, this supports my hypothesis in saying that water uses up more space in the dilution of catalase and will thereby; restrict the number of available active sites in the enzyme. This also means that fewer enzyme-substrate complexes will be produced. Alternatively; the lower percentage of water (higher the concentration of catalase), equals a slower (or a decrease) rate of reaction.
I have observed my problem-question and have found the answer. It seems that when 50% and 60% of catalase is used, the reaction is not too fast or too slow, however, it is still faster than the amount of concentration used below 50%. Here are my findings when analysing my results/graphs.
This further supports that the hydrogen peroxide’s role, as a substrate, when it binds successfully in the presence of a higher concentration gradient of catalase and less of water (the lock and key principle). Thus, a faster rate of the reaction, which is the reason that the rate increases when there is a lower volume of water.
The graph shows an increase in the volume of oxygen as the average initial reading of experiments conducted also increased. However, the graph explains how each reading increases in time to the volume of oxygen.
Nevertheless; many variables may have influenced my recording of that data. However; the data recorded seems to lie between each other so therefore; it enforces my hypothesis.
In the reaction where 20% of the catalase was used, .the reaction was quite slow, which therefore; produced less oxygen. There were less available active sites on the enzymes and more substrates. This means that there is an unbalanced ratio between the substrates and the enzymes, which further prove my hypothesis in saying that more enzymes increase the rate of the reaction. I found that there was one anomalous result that occurred after 4mins, the VO2 produced was at 3.3cm3.
In the experiment where I used 30% of catalase, the rate of the reaction increased, in comparison to the 20%. The volume of oxygen also increased as the time allowed also increased. However; I found two measurements that looked like an anomalous result as the graph had a distinct pattern. This occurred after 2mins of the experiment – quite early on – and happened again after another 4mins.
On the 40% of catalase reaction; as predicted the rate increased. As there were no anomalous results; the pattern in the graph was clear and distinct. The volume of oxygen increased as the time increased accordingly.
After using 50% of the catalase, I found that similarly to the 40% the pattern was clear on the graph. There were no anomalous results, but unlike 40% the rate of the reaction was balanced as it had another 50% of water to dilute it. Nevertheless; the reaction was much faster as there was less water used in this reaction than the rest.
When using 60% of the catalase in the solution, I found that there was less water to dilute the concentration, therefore; the reaction was faster as it had less water to slow it down.
The reaction that had 70% of catalase was the fastest in my whole experiment. This was because there was less water to dilute the reaction and its speed. Therefore; there were more enzymes to bind onto the substrates (which stayed constant). This ratio compliments in saying that increasing the enzymes produces more enzyme-substrate complexes, thereby; a faster rate of reaction can occur.
In conclusion; the reactions used in my experiment can help me prove my hypothesis in saying that as the percentage of catalase is increased in the solution; the faster the rate of reaction. In addition; the volume of oxygen also increases in time to the increase of the catalase. Nevertheless; a strong factor affecting the rate of the volume of oxygen produced is the addition of water. This because as the catalase is diluted, the reaction is slowed down, this is due to the water molecules getting in the way of the production of the enzyme-substrate complexes.
Finally; from this experiment, I have come to a conclusion that the higher the rate of the reaction at the end of the experiment, the higher amount of catalase used (and less water involved) in the reaction. I also decided that the anomalous results were the recordings that were influence by factors affecting the rate of the reaction.
I will compare the gradients of the reaction by observing the rate of the reaction and time ratio.
The table shows that the rate of reaction is bigger then the reaction is bigger. Therefore; the steeper the gradient, the slower the rate of the reaction.
Based on my gradient, I have taken into account aspects that could have assisted me before I began the experiment. This was firstly; the Lock and Key Principle, which explained how the enzyme-substrate complex was formed. It also explains how consequently, in addition to this new complex, oxygen would be released.
From my results, I have come to the conclusion that:
- If the temperature of a solution is raised, so is the time for the reaction to occur. When temperature raises so does the energy between the atoms. Therefore; an increase in collisions.
- An increase in enzymes means that the rate would increase as more and more enzymes collide with the substrates, faster and faster.
- When more collisions occur, the new product is made much faster.
- An increase in water slows down the number of collisions by diluting the energy that normally assists in a fast rate of reaction.
- When an inhibiter is added to the reactions, it somewhat disables the function of the enzyme so that the reaction is slowed, during non-competitive inhibition. It does also, however; increase the collisions as it manipulates the function of the enzymes so that the
- substrates can try to bind to its active site – this is competitive inhibition (above diagram).
I believe my method in the experiments and results were correct as they were controlled to a level that made them precise, exact and fair.
In conclusion; the constant steadiness and the ways in which I have structured my experiment, permitted me to allow the reactions to proceed carefully and correctly. This has lead to valid evidence, which has become reliable evidence that further maintains accuracy in my hypothesis as I set to prove that; as the concentration of catalase is increased, the volume of oxygen produced also increased, hence; a faster rate of reaction.
Evaluation:
The results for the unpeeled potato displays a faster rate in which the catalase was most effective. This means that the unpeeled potato allowed more enzyme-substrate complex’s to be formed, thus; a faster rate of reaction. In addition; by looking at the peeled potato’s graph, one can see that the both concentrations of the catalase had not completed its reaction. This was because; the reaction proved to be exceptionally slow in comparison to the unpeeled.
The unpeeled potato proved to be fast, especially when 80% of the catalase was used. However; the concentration, which had the 70% of catalase shows on the graph, a correlation that begins by accelerating up the graph. After this, the enzyme-substrate complex’s are no longer made as they have all bonded, this means the correlation then does not continue to increase up the graph and is, therefore; stationary. The reaction that has the 80% catalase in the solution had a different pattern. This was probably due to anomalous results, however; the results all accelerate across the graph as the time improves, thus; producing more gas. The reaction had not yet started to slow down on the graph, this may further prove that the higher the concentration of catalase; the longer the reaction can occur, thus; a faster rate of reaction. Had I continued after 10mins to record the readings with a burette that held more than 50ml, I believe that the reaction would have stopped to stay stationary is at the point the reaction is complete. Therefore; there are less available active sites to prolong the reaction.
In the peeled potato reaction, the trials for both concentrations of catalase were slow. Though both had a pattern that showed continuality throughout the experiment, however; there was a small different between the 50% and the 100% when there should actually be a doubled increase. This proves to me that there was less of a difference between the two percentages. It also means that there is hardly a big reaction occurring in the peeled potato (which implies that the skin of the potato holds the majority of the enzymes). As the enzymes increase, the rate of the reaction increases, also, however; as the peeled potato has less of a difference between its concentrations this means that even though there is an increase of the enzymes, it is lacking of the substrates that the reaction lacks to make it faster.
From this I conclude that the unpeeled potato is better during a reaction, than the peeled potato. This is due to the fast speed that the unpeeled potato has in comparison. The time to the volume of percentage ratio is constant in both graphs, as they both increase in proportion to each other. However; I choose to work with the unpeeled potato because there are enough substrates (even though it is constant) for the increasing amount of enzymes.
Finally, due to the results of my preliminary, I have decide to use six different samples of the concentrated solution. I will use these six reactions to determine and investigate my problem: how much catalase is enough to make the reaction a steady one. With this, I will investigate using 20%, 30%, 40%, 50%, 60% and 70% of catalase. This is because, I have noticed that too much catalase can make the reaction very fast, therefore, it would be difficult too record the data. Nevertheless, I still want to reaction high concentrations of catalase to determine their rate of reaction.
Though the experiment, to me, was fair and safe, I also think there could been aspects of the experiment that could of caused anomalies. This is probably because, they were small things that create large problems and could affect the final results. From these, one can decipher the improvements in the experiment. In addition; these aspects could also be linked to the factors affecting fair results/ accuracy and precision (also see above):
Firstly; when using the delivery tube, to pass up the burette, the bubbles that are move up into the burette from the solution, in the conical flask, get blocked between the tip of the delivery tube and the bottom of the burette. This can cause the rate of the reaction to be slowed down, due to the simple fact that the bubbles would not float up, as they are supposed to. As one of the aims in this investigation is to also collect the volume of oxygen produced, it was essential that all the gas particles move in their time limit. Not only would the results be unfair, but because the total volume of oxygen had not been collected, the results would therefore; become inaccurate. However; this problem can be solved by removing the gas that is blocked, and so allowing other gas particles to go through. Do to this a gas syringe can be used in placed of the bung, on top of the conical flask and connected to the delivery tube. It would apply to the collection of any fluid or gas – almost like a filter. The error shown in the graph suggests that the rate of reaction was slow and that there is no increased pattern in the production in the volume of O2 to support the notion that: increasing the catalase also increases the rate of reaction.
It is important to read the measurements at eye level as standing higher than the meniscus can cause an error in calculations. This is because the liquid used in the burette is clear just like the burette so it would be easy to mistake the meniscus’s position for a drop of water falling down the side of the burette. To this resolve this problem put a coloured piece of card at the back of the burette so that readings are easier. Ensuring that I read carefully, my results can come out precise and exact. This can lead to the error of in accurate recording that can result in an unfair test and also inaccurate measurement. This could easily mislead the true purpose of the experiment. This will make the readings standout. A reason for this improvement is that it is simple and ensures precise and clear results.
Another problem linking to the reading of the meniscus is the position of the burette. As the burette is held upside down, by the clamp stand, it means that the tap would be at the top and the opening section would be at the bottom where the delivery tube would be put under. This means that I would be recording the results upside down, therefore; it is possible to write the wrong results.
It is critical to record the recordings according to the position of the meniscus. By squatting to eye-level, it would be more clear to see if the recordings are exactly in line with the meniscus or an inch away. This would mean that the result outcome can come out exact. However; if the reaction is quite fast it would be difficult to quickly read the meniscus before it moved down the burette. This would lead to an error that suggests unreliable and non-representative results. The reason for this improvement is that it is easy and will lead to accurate findings
If the results are recorded a couple of seconds after they are supposed to, the solution would have a longer amount of time to react, therefore; the results would become unfair. Hence the reason to have another person to assist during the reaction process. As the reaction can occur quite fast, one person could read the measurements while the other can watch the stop watch.
It is important to use two different pipettes or syringes so that a reaction doesn’t take place when the substances are mixed together in the pipette/syringe. This is important as the results can be very different than expected and, thus; can make the experimental predictions seem incorrect. It is therefore; essential to use to different equipment for various tasks to ensure that an un-timed reaction takes place, as well as fair testing and accurate results.
When measuring for the solutions, the measurements should not exceed 10ml. this is so that all the other percentage catalase can undergo the same measurements and therefore; the results can be found due to fair variables. However; if accidentally the measurements in the cylinder exceeds the 10ml limit, the problem can be solved by removing the excess using a pipette or a syringe.
A problem linked to this, is actual extracting of the liquid from the centrifuged amount. This was problematic as I was trying to measure out a proportion by using a pipette; I found that the large bits in the liquid would become wedged in the pipette. In addition, some of the large bits would only become a problem when put into the cylinder. This was when I would pour the 10ml solution in the conical flask, ready to begin the experiment. However; after tipping the solution in, I would find that at the bottom of the cylinder are the large bits of the catalase. This meant that the total measurement was not in fact 10ml but less. Therefore; the final results would be affected by this at it is unfair and imprecise. To avoid this problem, one must centrifuge properly ands accurately using advanced measuring equipment in order to liquidize the bits of the potato. This error would mean the results are inaccurate because the experiment involved inaccurate measurement and it is possible that some samples are higher then others.
It is important that the conical flask is not shaken throughout the reaction as it can seriously affect the rate of the reaction, thus; altering the results. The solution in the conical flask can react more effectively if they are shaken. This is because; the atoms of the enzymes vibrate more and therefore; collide into the substrates, which increases the reaction rate. To make the reaction occur but still have a fair test, the conical flask should only be shaken a the beginning of the reaction to initiate collisions, after this there should be no more shaking. This rule should be constant in all of the experiments.
Another factor is the repeating of the experiment. This can not only make it a fair test but can also help achieve accurate average results that can then be plotted onto the graphs. Nevertheless; I feel that results are better found when the experiment is repeated more than once, as this can better back up my hypothesis and therefore; prove my results correct.
It is important to maintain the accuracy of the temperature so that the variable is constant. The experimental reaction in all the percentages of the catalase should occur during a room temperature environment. This is because, this is the normal and best temperature that the enzymes work best at without denaturing or having minimum effect on the whole reaction. However; there might have been another reason why the rate of the reaction was fast due high percentage of concentrated catalase, as it could have been in the influence of the temperature.
I also think that the depth the of the water in bath tub should also be constant as when the burette in put into the tub, the water surrounding adds pressure, which can affect the speed in which the gas particles reach the surface of the burette.
When beginning the reaction, the bung should be put on top of the conical flask immediately so that the gas particles can be collected in the burette. This can prove tricky to do because at the same time, the stop watch should be activated. To solve this problem, it is best if another person assists in pressing the button on the stop watch while you close the top of he conical flask quickly. This can lead to the error and lead to unfair and inaccurate results. This can also suggests that the results do not show the precise measurement recorded. It means that the reaction was in fact running for more than the time limit of 2mins.
Finally; I were given another opportunity to rewrite my method, I would want to test a theory in which I would change the concentration of the hydrogen peroxide instead of the catalase. This is so that I can watch the reaction occur according to the results that I have achieved in this current experiment. This can either back up my current experiment or can alter my hypothesis in such a way that can also change my results. With this hypothetical experiment I can observe how an increase of the hydrogen peroxide could have in effect on the constant concentration of catalase.
References:
-
Exam Revision Notes - Bill Indge © 2000;
-
Advanced Biology Through Diagrams - W. R. Pickering © 1998.
