As a result, the speed of the reaction slowed down, since there were fewer enzymes to do the job.
Consequently, we concluded this preliminary investigation by saying that:
“As the temperature increased, the rate of reaction increased accordingly, nevertheless, at a certain temperature the enzymes denatured which slowed down the rate of reaction significantly.”
Method:
1. Firstly, we put on our goggles and place a measuring cylinder on the table. We then measure out 5ml of Hydrochloric acid into the measuring cylinder, and then pour it into a test tube. In the same measuring cylinder we measure out 5ml of milk, and then pour this out into the test tube as well.
This will mix the two solutions of Hydrochloric acid and Milk together. As milk proteins can be broken down quicker by Hydrochloric acid than it can by trypsin, we are using this small, pilot experiment to provide us with an example of what a reaction of trypsin and milk protein would look like when completed, so we know when to stop timing.
2. We then commence the investigation by measuring out 5ml of trypsin into a measuring cylinder.
Then we put 5ml of milk in another measuring cylinder, however we leave this cylinder alone for a while. This is because the milk has been kept in a fridge overnight and therefore to keep the investigation a fair test we need to make sure that the milk is at room temperature when we use it. Every minute, we will check the temperature of the milk with a thermometer, to check whether or not the temperature of it has risen to 22°C.
3. Once the milk has reached room temperature, we can mix it with the trypsin and begin our investigation.
We must make sure that we start the stop clock as soon as we have added the milk to the trypsin. We will stop the timing when our substrate looks like the liquid inside the test tube that we made earlier, involving Hydrochloric acid and milk.
We will mix the milk with different five different concentrations of trypsin: 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%. For each concentration we will repeat the above test twice, to make sure that the results we collect are not mistakes.
Precautions:
As a precaution, I have limited my contact with the test tubes, as my body heat will raise the temperature, increasing the rate of reaction. I will also monitor the temperature using a thermometer so that I can ensure that it stays constant and does not disrupt the results of the experiment. I have also, when filling a measuring cylinder with trypsin, placed it first on a flat surface so that its measurement can be taken accurately. Also, I have read the measurement from underneath the meniscus and not the top.
To ensure that quantities of the various chemicals are measured accurately, I have used the smallest pipettes or measuring cylinders for each quantity. For example, to measure 5ml of trypsin, I used a 5ml pipette. In this way, more accurate measurements can be made since more detailed gradations are available on the apparatus.
Safety precautions that have been taken are the wearing of goggles throughout the experiment to avoid chemicals getting into the eye.
Fair Test:
To keep this investigation a fair test I will make sure that I will always measure out exactly 5ml of each substance before I mix them. This will help me to get more accurate results, as there will not be too much or too less of each material in the final mix. Also, I will make sure that the milk is at room temperature when it is utilised in the in investigation. This will also help to give me more accurate results as the milk will not be cold/warmer in temperature than the temperature of the substance that it will be mixed with it.
The variable in this experiment that I am going to keep the same is the trypsin concentration. The trypsin needs to be kept the same as I am going to do three different experiments with the same concentration. Therefore I will get different results if I accidentally use a different concentration in the same experiment.
Observation
Results:
My results have been repeated three times for each concentration to make them more reliable and accurate. The results are also correct to the nearest second so they can be precise to work with after the average has been taken.
Conclusion
My graph shows fairly weak, negative correlation. We can see a clear pattern between the two variables that as the concentration increases, the time it takes for the reaction to occur decreases. Therefore, we can turn this observation into a statement and say that: “the higher the concentration, the faster the rate of reaction.”
The blue points on the graph are mean averages of the three original experiments. As we had done three initial experiments for increased reliability; this was done to round them into a figure that could be an even more consistent adaptation of the three results.
My results do support my initial prediction. I said that the higher the concentration of trypsin, the faster the rate of reaction would be, and my results backed this hypothesis. There were more trypsin molecules in the milk, which increased the probability that the trypsin molecules will collide with a milk protein.
Evaluation
I do not think that my experiment produced accurate results due to the number of repetitions we did for each concentration. We did this number of repetitions to make certain of the previous result, and confirm that it was not a fluke. However, we did too many repeats of a result, which was an unnecessary waste of time and also, the three repeats we did for each concentration, had to be averaged using the mean method and this made each result progressively imprecise. In spite of this, an advantage of doing this number of repetitions is that it made the results more reliable to work with, as each result had been checked three times to make sure it was exact. To fix this problem and inaccuracy, I would have re-planned the experiment to do only two repetitions of each result. This number of repeats would have ensured a decent amount of reliability along with a good level of accuracy. Also, I think that the spread of the concentrations tested was not broad enough, as all of the concentrations tested were under 1%. I would have conducted the experiment using higher concentrations, such as 2%, 4%, 6%, 8%, and 10%. This would have made the experiment more reliable as the concentrations are spread, and not just from one ‘area’.
My graph has one anomalous point. The result of the concentration 0.4% is measured at 169s and it is the point that is the farthest away from the line of best fit. The reason for this point being anomalous is due to the fact that the result that preceded this one (0.2%) was a very high one at 366s. This high 0.2% result contrasted greatly to the low 0.4% result on the graph as there was a big difference between them, and the outcome was that the 0.4% point became anomalous.
My results are reliable enough to provide enough evidence for my conclusion because of the number of times they have been repeated to confirm them. However, as I have already mentioned, I do not think they are accurate enough to provide evidence for my conclusion because of the number of repetitions, which when averaged, made them very imprecise.
To provide more evidence to support my conclusion, I could conduct further experiments related to this one. For example, firstly, I could test the effect of concentration on the rate of reaction on other enzymes too, whose results could be used to back or test the conclusion found in this investigation. One example of this kind of experiment would be the reaction between hydrogen peroxide and liquidated celery.
It could also have been hydrogen peroxide on a liver, but this reaction much too quickly to be able to record the results with any accuracy.
This is because the liver has too many catalase enzymes, so the reactions are made a lot quicker making the investigation unfair.
The experiment will be conducted as follows:
Apparatus:
- water basin
- conical flask
- bung,
- delivery tube
- measuring cylinder
- syringe
- spatula
- stopwatch
- electric scales (for increased accuracy)
I will be timing the amount of oxygen that passes through the delivery time in a certain amount of time, after mixing the celery and Hydrogen Peroxide.
I will take measurements from the side of the measuring cylinder every 30 seconds and note them down. From my results I would have found that the higher the concentration of hydrogen peroxide, the quicker the reaction rates producing oxygen.