Investigating anaerobic respiration in yeast

Problem statement:what are the product of fermentation?

Procedure :

1. Prepare 2 boiling tube and label it boiling tube A and B2. boiling tube A is filled with 5 ml of yeast suspension and 15 ml

of boiled glucose solution3. boiling tube B is filled with only 15 ml of boiled glucose

solution4. A thin layer of paraffin oil is put on top of the contents of both

boiling tubes 5. boiling tubes are corked with stoppers with delivery tubes6. the end of each delivery tube is placed into a test tube filled

with 2 ml of lime water7. the initial temperatures of the contents in both boiling tubes are

recorded8. the apparatus is left aside for one hour9. after one hour, the final temperatures are recorded and the

change in lime water is noted10. the stoppers are removed and any smell that is released

from the boiling tubes is noted11. the results are recorded in the table

results

Boiling tube A B

At the beginning of the experiment

At the end of the experiment

At the beginning of the experiment

At the end of the experiment

Temperature (C) 30 31 30 30

Lime water clear cloudy clear Clear

Smell Smell of ethanol is not detected

Smell of ethanol is detected

Smell of ethanol is not detected

Smell of ethanol is not detected

Discussion

1. an aerobic condition occurs when a glucose solution is boiled and paraffin oil is added to cover the glucose solution. This prevent air from dissolving in the glucose solution. The glucose solution is boiled to remove dissolved oxygen

2. test tube B is set up as a control experiment3. after one hour the contents of boiling tube A are cloudy and foamy

whereas the contents of boiling tube B remain clear and non foamy4. anaaerobic respiration occur in boiling tube A because the lime water in

test tube A turns cloudy, the temperature of the contents increases and the smell of ethanol is detected

5. the cloudy lime water indicates the presence of carbon dioxide. The increase in temperature indicates that heat energy is released. The semll of ethanol confirms that anaerobic respiration has taken place in boiling tube A.

6. the process that has taken place in boiling tube A is fermentation.7. Fermentation by yeast produces ethanol, carbon dioxide and energy

conclusion

in the absence of oxygen, yeast undergoes anaerobic respiration to produce carbon dioxide, ethanol and energy. The hypothesis is accepted