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An Investigation to find out how Temperature Affects Respiration in Yeast.

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Introduction

An Investigation to find out how Temperature Affects Respiration in Yeast. The investigation is intended to demonstrate the way that respiration in yeast is affected by temperature. I have read up about respiration in yeast in Letts GCSE Study Guide, B S Becket's Biology A modern introduction and Illustrated Biology, and Tortora Funke Case's Microbiology An Introduction. This is my summary: Respiration is the overall process of breathing, gas exchange in the lungs, and the breaking down of chemicals to provide energy in living things. Most organisms require a constant supply of oxygen to respire. During cellular respiration, the oxygen is combined with glucose that has been converted from food. Energy is released, together with the waste products of carbon dioxide and water. This method of respiration that uses oxygen is called aerobic respiration. The other method of respiration, when no oxygen is needed, is called anaerobic respiration. One such reaction is fermentation. During this reaction, glucose is broken down into ethanol and carbon dioxide. Aerobic Respiration. 6O2 + C6H12O6 ? 6H2O + 6CO2 + 2900Kj oxygen + glucose ? water + carbon dioxide + energy Anaerobic Respiration. C6H12O6 ? 2C2H5OH + 2CO2 + 84Kj glucose ? ethanol + carbon dioxide + energy Yeast can respire using either method of respiration, though if in aerobic conditions yeast does not usually respire anaerobically. ...read more.

Middle

I predict that a graph showing how yeast respires at around 30-40?C would look similar to the second graph opposite. While the yeast is respiring aerobically, carbon dioxide is produced faster than when the oxygen has ran out and the yeast is forced to respire anaerobically. Trial Experiment. Total volume of gas released when bath is heated up to: Time (minutes) 06?C 30?C 0 0.0 ml 0.0 ml 1 0.0 ml 0.0 ml 2 0.0 ml 0.0 ml 3 0.0 ml 1.0 ml 4 0.0 ml 1.5 ml 5 0.0 ml 2.0 ml 6 0.0 ml 2.5 ml 7 0.0 ml 3.0 ml 8 0.0 ml 3.5 ml 9 0.0 ml 4.0 ml 10 0.0 ml 5.0 ml 11 0.0 ml 5.5 ml 12 0.0 ml 6.0 ml 13 0.0 ml 6.0 ml 14 0.0 ml 6.5 ml 15 0.0 ml 7.0 ml My trial experiment revealed one main problem. When the water bath is at temperatures above or below room temperature, the air contained in the armed conical flask and the yeast suspension either expands or compresses, this either causes bubbles of air to escape into the measuring cylinder, or water to be sucked up the delivery tube. I shall take this into account during my experiment and dedicate the first 3 minutes to letting the apparatus reach the correct temperature. ...read more.

Conclusion

* The rubber cork may not have totally sealed the flask. The equipment I used was not to the level of accuracy need to collect reliable data. Ideally I would liked have used this equipment: However, even if I had used this equipment, the following factors may still have caused inaccuracies in my results: * The yeast may have been defective. * The yeast suspension I used may not have contained the ideal concentration of water and sugar due to human error during preparation. * The yeast suspension, armed conical flask, and air contained within the armed conical flask may have been contaminated with substances that could have affected the yeast's ability to respire. * The yeast suspension, armed conical flask, and air contained within the armed conical flask may have been contaminated with organisms that also will produce a gas during respiration. * Due to human error, the volume of yeast suspension used during each set of readings may have fluctuated. * The temperature of the electronic water bath will have fluctuated, since it uses a thermostat. * The clamp stand would cause the temperature of the armed conical flask to be imprecise. * Human error may have caused the stopwatch to be started too early or late. If I were to repeat the investigation, I would take some readings of how the yeast respires at temperatures above 60�C. This would probably show ...read more.

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