Sugar Pyrex water bath
250ml conical flask Measuring cylinder
Bunsen burner Tripod
Oil Spatula
Thermometer Stopwatch
Large beaker
Preliminary Skeleton Method
Put a sample of yeast and sugar into the bottom of a conical flask.
Put a layer of oil over the top to seal off the oxygen, to make it anaerobic.
Giving the yeast and sugar a good temperature, food supply (glucose) and water these elements would speed up the process of fermentation.
I would put the conical flask into a Pyrex water bath and place it on top of a tripod and put the Bunsen burner underneath this.
Then use the tube from the conical flask and place it into a glass beaker with an amount of water in it, in this a small measuring cylinder turned upside down containing water.
This is placed over the tube so when the water in the Pyrex water bath is heated the amount of carbon dioxide produced can be measured. This is called downward displacement.
I could change the temperature of water and record its effects on how much carbon dioxide is produced.
I will record for 15 minutes and for every 5 minutes I record measurements on the measuring cylinder.
I will have to be as precise as possible when increasing the temperature of the water with the Bunsen burner and keeping it at one particular temperature might prove to be difficult. To make the investigation as fair as possible I will have to be very accurate with my measurements of how much yeast and sugar I would use and the accuracy of temperature of the water, etc.
Results (preliminary)
For the preliminary experiment I measured the amount of carbon dioxide produced 2 minutes after a temperature is set and recorded my results in a table as shown below:
- 6ml
- 10ml (6ml+4ml)
- 16ml (10ml+6ml)
- 26ml (16ml+10ml)
- 36ml (26ml+10ml)
Preliminary Analysis
I soon realised when looking at my preliminary experiment results that my results did not show what I expected to happen at all. I realised that it was not my method that was at fault but the way I was recording my results. I found that by taking only one measurement of carbon dioxide produced at any one temperature meant that I would have nothing to compare my results with and therefore have no clue to how reliable they would be. I also found that I was not calculating the measurements correctly and the units of carbon dioxide were incorrect. So I took this as a good learning experience to find out what were the faults in my experiments and now know how I could improve it for the beginning of my actual experiment. I can use this information to make certain changes to make my results reliable and produce a more accurate method for collecting my results.
The preliminary experiments were most useful and have shown my how important it is to carry out preliminary work for the benefit of the investigation. My conclusion to the preliminary experiments is that my method of the experiment I can keep the same but simply change the way of measuring the carbon dioxide in the measuring cylinder and recording much more accurately.
Results using final method
I took three measurements because I found from using my background information that it was more accurate to take three measurements. As in some cases the gas collected can be different therefore collecting the gas at one particular temperature means you will end up will a more accurate sample of gas. The measurements are taken after 2 minutes after the temperature has been reached:
1 2 3
30 1ml no more gas produced no more gas produced
40 6.8ml 4.2ml 8ml
50 10ml + 6ml 2ml
60 8ml 1ml 2ml
Graphs to show the results are on the next few pages
Results
Conclusion
My aim at the beginning of this investigation was to find out the effects of temperature in the process of fermentation. My prediction was that when I reached the temperature of 40 the amount of carbon dioxide produced would be at its greatest. From the final set of results I gathered I found that this confirmed my earlier predictions. In my prediction I also stated that after 40 the enzymes in the yeast would be ‘denatured’ because the enzymes had passed their optimum temperature, therefore less gas would be produced. This is also shown clearly in my result table.
During my investigation each temperature I measured the amount of gas at, I took three results. My purpose was to establish an accurate measurement of carbon dioxide. As for the first two sets of results the amounts of gas measured are much higher than the third proving that when the first two measurements were taken more than one gas was produced. In conclusion the results from the third measurement at each temperature are the most accurate samples for the investigation. My results are reliable as they conclude an enzyme theory using the fact that the enzyme optimum temperature is 40 .
From looking at these results you can see how at 40 8ml of carbon dioxide was produced, then at 50 and 60 only 2ml of carbon dioxide was produced. This confirmed the theory I made in my prediction earlier in my investigation. As at 40 the enzymes in the yeast are at their optimum temperature, more gas is produced at this time and beyond this temperature the enzymes become ‘damaged’ or ‘denatured’ and are no longer able to carry out their specific job efficiently.
I am able to look back at my original information in my plan, at the beginning of my investigation. I can conclude that when there is a good supply of food and water, and a suitable temperature budding does occur at a much faster rate which produces more carbon dioxide if enzymes have better conditions. From my results I can establish that when the temperature is increased by 10 the rate of reaction almost doubles.
By looking at my results I can correspond with the scientific ideas from my plan about the explanation of involvement of the enzyme.
By looking at the diagram above you can see that if we speed up the reaction time by increasing temperature the amount of energy producing more collisions within the active site of the enzyme. What we must remember is that when the temperature is raised to 40 the active site of the enzyme is denatured therefore less carbon dioxide is produced.
On the next page there is a graph to show how the last measurements taken at each temperature showed the reliable pattern of how the enzymes became denatured after 40 .
On the further next page there is another graph show the averages of the temperatures used in the experiment and what they show. Also showing the supporting evidence for the mathematical prediction being correct.
A graph to show the final results I collected from my investigation
Evaluation
In my results from the investigation I found that I did not have any anomalous results as such because of how I recorded my results. The first two sets of measurements are unreliable. During the experiments I first recorded them as anomalous results as they did not show any relationship to the third set. It was later that I established an understanding that more than one gas was produced when the first two measurements were taken.
I believe my results to be relatively reliable, although I did encounter some problems during the investigation. One of my main problems, which I managed to overcome in my preliminary experiments, was the way I recorded my results. I learnt from this and was able to establish a way of taking more than one measurement of gas at a particular temperature, enabling me to have a wider range of results. Also by doing this it would be clearer to see if my results had any patterns or any anomalous results.
There were some experimental errors, improvements I would make if I were to make my results more reliable would be to measure precisely how much oil I used in the conical flask. As I did not carry out all of the experiments at the same time, therefore using different apparatus and slightly different volumes of oil. It may seem like a small thing but it’s the small things that matter and make the most difference to the reliability of the results. There were other problems such as the problem keeping the constant temperature while taking three sets of results at one set temperature. The thermometers that we used were unreliable as some didn’t work and some were damaged, etc. To improve the use of thermometers in the future you could look for an alternative, which might be more accurate. The possibility of human error also, concerning poor time keeping when it came to taking measurements.
Other aspects of improvement could be taken by counting the number of yeast cells in the microscope’s field of view, you can follow the development of the yeast population. You can also use other apparatus such as a counting slide which is used by dividing it into four squares and the number of yeast cells in each square is counted at the same magnification each time.
There is also the question of what state in the yeast growth cycle the samples of yeast’s we were using during the investigation. There are 4 main stages in the yeast growth cycle:
Lag phase
Rapid growth
Growth slowing
Population constant
In the investigation my aim was to get the yeast into the two middle stages of rapid growth and growth slowing. As the fermentation process reaches a certain point it stops. This is because the enzyme produces carbon dioxide and alcohol, the alcohol acts as a poison on the yeast population and kills the yeast.
If I were to do any extension work concerning this investigation I would look into the optimum temperature of the enzymes. I would find a method to try and test the temperature around 40 to see how much carbon dioxide is produced just before and after to see how the enzymes deteriorate after they have reached their optimum temperature. You could also look at the gases that were produced along with the carbon dioxide collected in the first two sets of results. I would have to research how I could test to see what the gases were, I would then be able to distinguish what was carbon dioxide and what wasn’t at the particular temperature. Also if I were to investigate further I could use different types of sugar or yeast. These are all different paths I could look into.
There are many other ways you could take this investigation but from this aspect of how temperature affects fermentation has been very successful. From taking it further I could only learn more about fermentation.
