2. This is a kind of respiration which do not require any oxygen. Only some of the organisms can perform anaerobic respiration, eg. Certain bacteria and fungi. In anaerobic respiration, glucose is only partly broken down. Much less energy (ATP) is produced when compare with the aerobic respiration. What is Anaerobic Respiration?

3. Glucose Energy + Ethanol + Carbon Dioxide THIS IS THE WORD EQUATION!

4. C 6 H 12 O 6 ATP + 2C 2 H 5 OH + 2CO 2 This is the Chemical Equation!

5. Alcoholic fermentation is the basis of wine making. However, ethanol is toxic to yeast. We conduct this experiment to investigate the effect of concentration of ethanol on anaerobic respiration. D D

6. Since ethanol is toxic to yeast, as the concentration of ethanol solution increase, the yeast is inhibited to carry our respiration, so we estimated that the anaerobic respiration rate of yeast will decrease as the concentration of ethanol solution increase.

7. As yeast will carry out anaerobic respiration in the absent of oxygen, ethanol will be given out which is poisonous to yeast and respiratory rate of yeast is then slows down. This can be shown by drops in the increase in air pressure in each syringe as the volume of the syringes are kept constant. As carbon dioxide is produced during anaerobic respiration, air pressure inside syringe is increased which can be detected by the low pressure sensor.

8. Syringe x 6 Beakers x 6 Short rubber tubing x1 Computer x 1 Data logger and low pressure sensor x 1 Electronic balance x 1 2g Yeast 10 cm 3 of glucose Distilled water 10 cm 3 of pure ethanol

9. 1. Set up the computer and get Science Workshop ready 2. 6 syringes and 6 beakers are prepared, and labelled 1,2 to 6 3. Weigh 0.25g of yeast in electronic balance for each syringe 4. Mix X cm 3 pure ethanol and Y cm 3 distilled water, 1.25cm 3 glucose, 0.25g of yeast into each beaker according to the table below

10. X cm 3 of water and Y cm 3 of ethanol 20 Total volume (cm 3 ) 1.25 Volume of glucose solution (cm 3 ) 32.41.20.60.30Y cm 3 of ethanol 15.7516.3517.5518.1518.4518.75X cm 3 of water 1512631.50% of ethanol solution 654321Syringe

11. for example, in syringe 2 total volume = 20 cm 3, for 1.5% ethanol solution, volume of ethanol added: 20 x 1.5% = 0.3 cm 3 volume of glucose solution added = 1.25cm 3 volume of water added = 20-1.25-0.3 = 18.45cm 3

12. 6. The syringes are filled by the mixture in the beaker through the nozzle by the plugger 7. A free end of rubber tubing is attached to the nozzle of the syringe, another end is attached to the low pressure sensor connected to the data logger 8. Data is then recorded as a graph 9. Repeat the above steps in order to obtain result for 6 syringes 10. Take the slope of the graph of each syringe 11.The change in pressure / change in time = slope = rate of anaerobic respiration

13. Setup for the Experiment

14. The result in our first attempt to the experiment

15. The result in our second attempt to the experiment

16. Error + precaution 1. Some gas containing oxygen has entered the syringes, and yeast may perform aerobic respiration. 2. Leakage of gas may occur, the pressure is not accurate. R We can apply vaseline to the both connect tube and any junction 3. The concentration of ethanol solution is not exact because measuring cylinder is used. R We can use the burette instead of the measuring cylinder. 4. Temperature fluctuates. R We can wrap the syringe with some cotton wool or put in water bath, in order to maintain a constant temperature throughout the experiment.

17. From the graph, we can see that the slope is negative which means that as the concentration of ethanol increase, the rate of respiration of the yeast decrease gradually. The increase in concentration of ethanol inhibit the yeast to perform respiration since it is poisonous to yeast. I I I I I

18. By : Herby Cheung (5) Margaret Ng (19) Karen Wong (24) 6AS Celene Ho (13) 6B H H