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Anaerobic Respiration of Yeast.

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Introduction

Anaerobic Respiration of Yeast Aim: To investigate the effect of temperature on anaerobic yeast respiration. Basic outline plan: I plan to force a solution of yeast and glucose to anaerobicly respire. I plan to measure the gas collected at allotted intervals during a set period of time, when the solution is at different temperatures. I will need equipment to accurately measure the volume of gas collected, and an indicator to show me that all no oxygen is present in my solution. I will also need to make a way to force it to anaerobicly respire by creating an air tight layer over the top of the substance. Prediction & Background information: I predict that a gas will be given off and this gas will be CO2 as we are anaerobicly respiring yeast. We know that Anaerobic Respiration In yeast has the following formula. Glucose Carbon Dioxide + Ethanol + Energy C6H12O6 2CO2 + 2C2H5OH + 210 KJ/Mole. I predict that the volume of gas expelled will increase with temperature. I believe this for a few reasons. The first is due to the 'Kinetic theory', this states that the extent of a molecules movement depends on its state and temperature. ...read more.

Middle

Method: The big beaker was filled up half way with tap water and using the thermometer the temperature was measured, the first temperature is 25?C so if it is too cold, hot water from the kettle, or even the hot tap should be added if it is too hot add ice to cool the water down. When the temperature is right our pre prepared solution of Glucose and Yeast should have around 4-5 drops of Diazine green added to it and sealed with a layer of liquid paraffin. The flask should be corked and shook, and then the solution should be allowed to settle. The flask should be placed into the prepared water and allowed to equilibrate to the temperature for 5 minutes, making sure the temperature of the water bath is still 25?C, if after 5 minutes the solution hasn't changed to a pink colour allow it to stand in the water bath until it does change to a pink colour. This will show you there is no oxygen present in the yeast solution so anaerobic respiration can take place. Now the water bath with the flask still in it should be placed near the gas syringe, ready to place the delivery tube's cork over the top of the flask. ...read more.

Conclusion

I thought my method allowed the results to be sufficiently accurate although we did run the risk of killing the yeast by its own ethanol which could disguise itself as denaturing. I think my results were reliable enough to support the conclusion especially due to the fact that there are no obvious abnormalities. There are a few results hat do not fit the overall trend such as the cumulative amount of gas expelled as shown on graph 1 does not quite fit into a curved line but still however shows a general trend. If I was to test the same variable again I think I would have pre boiled my glucose and water solution with a paraffin layer already coating it and then add a yeast tablet, so we would not have to wait for the oxygen to disperse. And I would also use an electric water bath to heat the water each time, with an electric thermometer to achieve more accurate results. If I could make the water bath very accurate I would test every degree for a 10� period between 40� and 50� to discover exactly when the optimal point for this yeast enzyme is. ...read more.

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