The formula for anaerobic respiration is:
glucose + alcohol carbon dioxide + energy
As with aerobic respiration, carbon dioxide gas is given off. Alcoholic fermentation is far less efficient at giving energy than aerobic respiration. When one mole (180g) of glucose is respired aerobically, 2880kJ of energy are transferred. The equivalent figure for anaerobic respiration is 210Kj. A lot of energy is kept in the alcohol. This can be shown in the combustion of alcohol when energy is transferred into the surroundings which, as a consequence, become warmed.
In conclusion, alcoholic fermentation is much less efficient than aerobic respiration but it can still supply some organisms with enough energy to maintain them when oxygen is low.
One example of an organism that is able to respire anaerobically is yeast. It is a single celled fungus which can be found in fruit, feeding off the fructose. It multiplies rapidly by budding.
Yeast has three main uses to humans: in the making of alcoholic drinks, the making of bread and the production of fuel.
The following will be used in the final experiment.
Apparatus:
250ml beaker, delivery tube, 2x test tubes, stopwatch and test tube rack. Glucose, yeast, limewater, and a very thin layer of paraffin.
Safety:
- Goggles and lab coats must be worn at all times.
- Substances must not be touched, tasted or smelt.
- Hands must be washed once experiments have been completed.
- Reactions must be observed carefully.
Fair Test:
- The seal between the bung and the test tube must be air tight.
- Use a thin layer of paraffin each time.
- Use the same amount of glucose solution and yeast each time.
- Experiment could be performed more than once.
Factors to control and vary:
For each experiment, the factors to control are the amount of glucose, yeast and liquid paraffin. The factory to vary is the temperature in each experiment
Preliminary experiment
Method:
The apparatus was set up as shown in the diagram below. Two test tubes were used in the experiment. One of which was filled to about half its volume with limewater and the other with approximately 2cm³ of a glucose solution and yeast and a thin layer of paraffin on top to prevent oxygen from escaping. A delivery tube was fed from the test tube containing the yeast to the test tube containing limewater. These apparatus were then placed in different conditions. For example; some were placed in a beaker of ice or in a water bath at different temperatures. The test tubes were then examined after the experiment to see if carbon dioxide had been given off and the limewater had turned cloudy (the sign that CO2 is present).
Diagram:
Results:
Conclusion:
In conclusion, it can be seen that the most effective temperature for anaerobic respiration to occur is 30 degrees centigrade as this is when the most carbon dioxide is produced.
Prediction:
Based on the preliminary experiment and background scientific information, I predict that initially, as temperature increases, the amount of respiration will increase also but it will reach a peak at a certain temperature and any temperature increase after that it will result in a decline of the amount of respiration.
