An investigation into the optimum conditions for the anaerobic respiration of Yeast (fermentation).

                             Energy release = 1.17 kJ/g glucose

The energy released is less than in aerobic respiration.

Why is there a difference in energy output? Aerobic respiration completely oxidizes glucose to carbon dioxide and water and releases all the available energy from each glucose molecule. Anaerobic respiration converts glucose into ethanol or lactic acid. More energy can be obtained by oxidizing the ethanol or lactic acid aerobically.

Introduction To Enzymes

Enzyme means “in yeast” (zymase). Many chemical reactions take place inside a cell. The speed at which the cell reactions take place are controlled by catalysts called enzymes. Enzymes are proteins. There are thousands of enzymes.

Aim

An investigation into the optimum conditions for the anaerobic respiration of Yeast (fermentation).

Apparatus

Method

1. Firstly make up a mixture of 15g of yeast, 15g of sugar and 5 ml water. 1 hour previous to experiment.
2. Set up apparatus as shown above.
3. Draw up a table showing temperature, Volume of CO2 given off in  6 minutes.
4. Use the water bath to heat the mixture to 23oC, remembering to remove the mixture from the water bath before heating the water.
5. Place the mixture back in the water bath and wait for the mixture to heat up to 23oC.
6. When the mixture has acquired the desired temperature start the timer.
7. Record readings from the gas syringe every minute for 6 minutes.
8. Stop the timer and reset both the timer and gas syringe.
9. Repeat stages 4-8 for the following temperatures 33, 38, 43, 46.
10. Calculate mean amount of CO2 produced per temperature.

Safety

While conducting the experiment I wore safety spectacles and a laboratory coat. I also made sure that there were no hazardous things around my working area and Bunsen burner. These are standard procedures that you should do before every experiment or investigation.

Hypothesis

I think that as the temperature rises the production of CO2 from the respiration of yeast will rise until it hits the optimum temperature from there on the production of CO2 will slow down till the yeast becomes denatured and then CO2 will no longer be produced. I predict that the optimum temperature will be between 40oC - 45oC although it may rise to 50oC although I do not think that, that will occur.

Results

 Interpretation of Results

My Results show that the optimum temperature for the respiration of yeast occurs at about 43oC the highest point on my graph. As you can see the as the temperature rises the volume of carbon dioxide goes up slowly until the optimum temperature. On the other hand after the optimum temperature the volume of carbon dioxide drops quite rapidly. In other words the enzymes catalyze the reaction. This catalysts work faster and faster until the optimum temperature when the active sight is denatured or deformed and less of the catalysts work which is why after the optimum temperature the volume of CO2 drops rapidly.

Conclusion

I conclude that the optimum temperature for the anaerobic respiration for yeast is 43oC this co-insides with my hypothesis. The shape of the graph is curved. The curve does not have a line of symmetry signifying that the enzymes are slow in terms of temperature to speed up the reaction compared with the rate that they denature.