Prediction
I predict that the concentration of 100% hydrogen peroxide will give out the most oxygen as the amount of hydrogen peroxide molecules are more compared to any other concentration. This is backed up by the collision theory which states that molecules have to touch to bond. Using this evidence it is safe to say that if there are more hydrogen peroxide atoms then the likelihood that they bond with the enzyme is much higher. If there are less atoms of hydrogen peroxide then the likelihood of them bonding with the enzyme is lower. The amount of Oxygen displaced depends on the bonding between the molecules and therefore this is a good indicator of how many reactions are happening in the solution.
The enzymes will also have to hit the molecules at the right angle for the molecules to dock unto the active site. The enzymes will very rarely touch the substrate if the concentration reaches below 10%.
Safety and risk assessment
Safety goggles will be worn to avoid any hydrogen peroxide reaching the eye. Scalpels will be used on tiles to allow stability when trying to cut therefore reducing the risk of cutting yourself.
After dealing with hydrogen peroxide the people involved will wash their hands thoroughly using soap and water.
The potato discs will be filtered and disposed off to avoid any accidental ingestion or incident of any kind.
Fair Test
To make it a fair test the following variables will be kept the same (controlled):
- Amount of potato disks
- Length of potato discs
- Temperature
- Sunlight exposure
- Time
The concentration of hydrogen peroxide will be the only variable that is changed.
The equipment used will have to be identical when a sample is being re-run therefore all the will be chosen and assembled prior to the experiment.
Trial run
During the first trial to see if the experiment worked there were a lot of complications which arose during the experiment. Firstly the bung did not fit our tube so it was impossible to fully close the tube containing hydrogen peroxide and Catalase. This unfortunately allowed some oxygen to escape into the atmosphere.
Next the tube didn’t stay in the measuring cylinder making it hard to collect the oxygen; most of the oxygen ended up escaping. The results therefore were all rendered anomalies.
Conclusion of trial run
From the trial run I have concluded that we will need to find an appropriate bung and also find a device to hold the measuring cylinder within the water. This will have to be done while someone is keeping the time.
Observation
Amount of Oxygen collected (cm3)
Averages
Amount of oxygen collected (cm3)
Analysis
I noticed that the 100% concentration total of water displaced therefore showing that 7cm3 of oxygen was produced. This total was made with 3 potato discs as with the other experiments. The charts showed that the 10% concentration of hydrogen peroxide produced only 0.7cm3 of oxygen. This shows a pattern that the less the concentration of hydrogen peroxide the less the oxygen produced showing that less hydrogen peroxide bonded with a Catalase enzyme. This proves my prediction correct where I stated that that the concentration of 100% hydrogen peroxide will give out the most oxygen as the amount of hydrogen peroxide molecules are more compared to any other concentration.
The concentration 0% was tested as a control to see whether it was the enzyme and hydrogen peroxide that were producing the oxygen or if it was just oxygen found in the air. The rate of reaction steadily rose on 100% however there was one anomaly that arose which seemed to influence the results.
Evaluation
The method to which I conducted the experiment seemed to be quick, efficient and affective, but there had to have been some problems with it which can explain why my results came out the way they did. There are many factors that need to be discussed so it can be understood why my experiment came out the way it did.
Firstly as we did not complete the experiment in one day and the potato got used up we used a variety of potatoes when conducting this experiment. This would have had an affect on my results because potatoes are all grown differently, some are older or younger than others, and have different catalase concentrations. Even in the same potato different areas of it contain different amount of catalase concentration. This in turns means that if different concentrations of catalase were being used during the experiment that my results would be inaccurate. I know this because in my research it clearly states that the catalase concentration has an affect on the activity rate. The higher the concentration of enzyme the more oxygen the more oxygen that there is going to be being produced. So the experiment would not have been correct because I was aiming to see what affect changing the level of substrate concentration would have on the activity rate. So if the catalase concentration was changed as well it was not have been a fair test because 1, it was not only the substrate concentration levels that were being tested and 2, because each of the different concentrations would have received a different catalase concentration level which would affect its activity rate. In my experiment I tried to keep the enzyme concentration levels at the same levels for each of the concentrations but as I didn’t do this accurately enough this factor played apart in inaccurate results I received from my experiment.
There was obvious human error in the experiment that can account for some part of the inaccuracies. To cut this down one person can do one particular job for each part of the experiment, which will mean that that person will carry out the readings and measurements in the same way. The reading error from the apparatus will be cut down if one person does it for example if two people read the amount of oxygen being produced levels one could round up when reading it off and the other could under read when reading off. At least if one person does it then at least all of the substrate concentrations would have the same inaccuracy so it would balance out. Another way of cutting down the percentage of human error is by not relying on eyes judgement when measuring out the hydrogen peroxide and the water but by also weighing it on a set of scales, which will be more accurate. Although the fact that there is a percentage of inaccuracy with the scale just like every other piece of apparatus would have to be taken into account. Some of the oxygen that was given off would have not been measured, as it would have been lost in the water as the equipment was faulty and was not completely airtight. As different amounts would have been lost for the different concentration, which means that there would have been different levels of inaccuracy for the each of the different substrate concentrations.
The experiment was conducted on different days and the apparatus weren’t always available. The different equipment would of all have a different degree of inaccuracy. However if we had used the same equipment throughout the experiment then there still would have been inaccuracies but that would have all been to the same degree for each of the different substrate concentrations.
Temperature is another factor that affects activity rate and the temperature that each of the different substrate concentrations had were not the same due to the following factors; the experiment was carried out in different rooms and some rooms have a higher temperature then others. The experiment was carried out at different times of the day and the temperature changes through out the day, which would change room temperature. The temperature should have been kept the same in order to keep the experiment a fair test. In my research I found out that enzymes work pest at around 40 degrees so we could have kept the temperature of the experiment constantly at 40 degrees in order to use the enzymes to there full potential.
To get more accurate results I have made a Modified Procedure:
Measure out the correct substrate concentrations ensuring you weigh them to increase accuracy.
Use the potato borer to cut the potato strips then cut them into 10x1cm strips with the scalpel.
Add the potato then put the stopper on immediately.
Measure the amount of oxygen given off into the burette every 30secinds for 5minutes.
Repeat the steps five times for each concentration ensuring that you use the same potato apparatus and that the temperature is kept constant preferably at 40 degrees.
Ensure that the same person is doing a particular part of the experiment throughout the whole experiment.
The reason that this new method will improve the accuracy of my experiment is because I’ve attacked the issues that I discussed above where possible.
