Set up the same test tube as above accept without a bung or a gas syringe
3. Collect CO2 using a fermentation tube.
The problems with these experiments are:
Syringe:
- It is relatively complex to set up so errors may occur in the readings.
- Air may become trapped between the oil and the yeast making the reaction aerobic.
Bubbles:
- The person could miss-count the bubbles.
- The bubbles may be of different sizes.
- Air may become trapped between the oil and the yeast making the reaction aerobic.
Fermentation tube:
- It is very complex to set up and so the chance of errors in the readings is increased.
- An amount of air may be trapped in the bottom of the tube causing the reaction to be aerobic.
- When the yeast is forced out of the tube by the gas, it then respires outside of the tube and so less is respiring inside the tube where the gas is being collected.
I have chosen to use the collection of CO2 gas be a gas syringe method. From Mckeane, I know that the optimum temperature for anaerobic temperature in yeast is 50oC. Therefore I will vary the temperature to see if this information is accurate.
I will carry out preliminary experiments to see if my range of temperatures is adequate for the experiment.
yeast + glucose → alcohol + carbon dioxide
Prediction
I predict that the maximum amount of CO2 will be produced at 50oC. I predict this because it is the optimum temperature for anaerobic respiration in yeast. In anaerobic respiration in yeast, I know that CO2 is given off. If the optimum amount of CO2 is given off at 50oC I know that the yeast is respiring at the optimum temperature.
Measuring + Observations
I will make sure it is a fair test by only having one variable and keep all other factors constant. The factors that could effect this experiment are: Amount of yeast, the pH of the yeast, the glucose (fuel) that the yeast has been given, the amount of air that should not be reacting with the yeast, the temperature of the yeast. I will ensure that this is a fair test by making sure that is only they temperature which I will vary. All other factors will be kept constant so as to not affect the results.
Range
I will take 3 readings at every temperature. I am using this number because I can formulate an average of the three, which should be closer to the actual amount. I will be taking the readings at 10oC intervals from 10oC to 60oC. I have chosen this range because it goes to distances above and below the predicted optimum temperature. I will be working to 1cm3 degree of accuracy for the reading of the CO2 gas. I plan to repeat all results that do not fit the trend of the other results in that temperature. This is necessary because it will bring my average of the temperature more reliable and so closer to the actual amount.
Apparatus
The apparatus I will be using in this experiment will be:
- Boiling tube
- Delivery tube
-
Gas syringe (20cm3)
- Bung
- Water baths at; 30, 40, 50, 60 degrees
- Test tube rack
- Ice
-
Beakers. (100 cm3)
Results
The bottom row of each of the table is the actual result collected. In the first 4 tables the bottom row refers to the amount of CO2 collected from the experiment.
Exp 1
Exp 2
Exp 3
In experiment 2 I received an anomalous result for thirty degrees I have disregarded this result, as it will interfere with my correct readings.
Average
I must know find out a rate of reaction of the anaerobic respiration in yeast. This is the formula I used to evaluate the rate of reaction:
Rate of reaction = Amount of CO2 collected
Time
Rate
Analysis
From my results I can see that there is a trend. For every 10oC increase in temperature the rate doubles. In my prediction, I stated that the optimum temperature was 50oC. In my results I found that 50oC was the optimum temperature for the anaerobic respiration in yeast. As I kept all me variables controlled (except for temperature) I know that any rise in the rate of anaerobic respiration is due to the change in temperature. From my results I can see that as the temperature increases to 50oC the rate of reaction doubles at every 10oC. After 50oC the enzymes must become denatured because the rate of respiration falls rapidly. However the increasing effect is called the Q10 effect.
Evaluation
The prediction I have made was correct to the nearest 10oC. The optimum temperature from my graph was 50oC. My results follow the Q10 effect. This is when the rate or respiration doubles for every 10oC. However not all of my results support my prediction. In Experiment No 2 at 30oC I found an anomalous result. The amount of gas collected was much lower than it should have been if it were to fit the pattern of the Q10 effect. This could be because I began to take measurements before the yeast had reached the temperature it was meant to be at, causing it to respire slowly until it reached the temperature.
In our experiment, small enough gas syringes were not available and were not as able to freely move. This meant we collect CO2 gas in an inverted measuring cylinder filled with water. If I had to repeat the experiment I would use the apparatus originally requested for. This would make my results more reliable because it is easier to read the measurements from a gas syringe than from a half submerged measuring cylinder. I chose not to repeat the experiment No 2 at 30oC because I had already obtained many other results at that temperature. By disregarding the anomalous result I am able to calculate a more reliable average and so my result will become more reliable.
I wish I could have researched the subject a little more but this however would only have reiterated what I had already found out. It would make me feel more confident of my conclusion. However, if I had done any more reading I am sure that I would not have found new material to change my conclusion but the same information to make sure my conclusion was correct.