Collision theory states that with an increase in temperature the reactants should move around faster and so the reaction should take place faster and so with an increase in temperature the glucose particles should move around and so react more with the yeast and the enzymes the inside the yeast cells but only up until 40oC, above which the enzymes will denature and become completely defective.
List of Variables and How they are Controlled
Independent Variable: The temperature; I will change the temperature to see how that effects the output. This will be controlled using an electric water bath for each temperature
Dependant Variable: I will measure how much Carbon Dioxide is released by the anaerobic respiration of yeast. This will be collected and measured using a gas syringe.
Fixed Variable: The amount of yeast and glucose I use will remain the same through out my experiment. I will also make sure the concentration of glucose is the same (10%).
Information from Preliminary work and Secondary sources
From my preliminary work I found that 1g of yeast reacting with 20ml glucose is suitable for this experiment, I also realised that I should use temperatures between 20oC and 60oC because below 20oC and above 60oC no results will be obtained.
Range of Conditions
I will use a range 40oC between 20oC and 60oC going up in steps of 10oC, apart from that I hope to keep all other variables and other conditions constamt.
Number of repeats
In an attempt to prevent any incorrect results or anomalies I will repeat each experiment 3 times or alternatively until I have a set of consistent results which I consider to be correct.
List of Apparatus
- Water Bath
- Hoffman clamp
- Gas syringe
- Delivery tube
- Bung
- 1g of yeast
- Beaker
- Water
- 20ml of 10% of glucose Solution
- Test Tube
- Stop Watch
Method
The apparatus will be set up as shown above with 1g of yeast and 10ml of glucose placed in a water bath of different temperatures. I will wait until the yeast and glucose has reached the same temperature as the water bath and there is a constant flow of bubble with in the reactants before putting the bung on the boiling tube. This reaction should produce carbon dioxide, which I will collect, and measure in the gas syringe. I will take measurements every minute for 3 minutes while the reaction is taking place. If there is a seemingly incorrect result then the experiment will be repeated, and after each temperature new apparatus and reactants will be used for the next.
Safety
I will be careful when handling hot water in fear of burning my self and those around me, and I will be careful when handling glass to ensure nothing is broken and no so there is no danger to me or anybody around me.
Explanation of Trends
Yeast respires because it forms a reaction with glucose; enzymes inside the yeast’s cells catalyse this reaction. The optimum temperature for these enzymes is 40oC, below this temperature they work less efficiently and yet above this temperature the enzymes denature and do not work at all. The way in which an enzyme catalyses a reaction is best described like a lock and key e.g a key only fits one sort of lock, like an enzyme is substrate-specific (it will only catalyse one reaction). A key is a fixed shape and so is an enzyme, but an enzyme denatures (changes shape) and stops working at too high a temperature, hence at temperatures too high above 40oC the enzyme worked less efficiently.
The results from this experiment support my prediction, in the way that I predicted the respiration of the yeast would peak at 40oC and above or below this temperature the yeast would respire less. Though my prediction stated that the enzyme would not work at all at 50oC, and it seemed in the experiment the yeast respired quite well at this temperature, and so that was a fault with my prediction though this error could be due to poor equipment and a poor method.
Evaluation
Accuracy of Results
The accuracy of my results is questionable due to the inaccuracy of the equipment used
Suitability of the Method
Improvements to Equipment and Method
Anomalous Results and Possible Reasons for them
Reliability of Results and how the Results Support my Conclusion
