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Effect of Temperature on the rate of respiration

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Effect of Temperature on the rate of respiration Introduction Respiration is the chemical process used by all living organisms to liberate energy in order to create ATP, Adenosine triphosphate, from food, usually glucose. When oxygen is used during the reaction it is termed aerobic respiration and when oxygen is not available it is known as anaerobic respiration. In aerobic respiration approximately 36 ATP molecules are produced and the pyruvate made during glycolysis is completely oxidised to form water and carbon dioxide. Anaerobic respiration is less efficient and only produces two ATP molecules and also uses the pyruvate by converting it, using a process of fermentation, into ethanol and carbon dioxide. Yeasts belong to the kingdom Fungi and are unicellular organisms that reproduce asexually. Yeasts are termed facultative anaerobes because of their ability to respire with or without oxygen. It is possible to view the process of respiration in yeast by placing a small sample of the unicellular organisms into water and observing the bubbles of carbon dioxide gas that are released. The speed at which fermentation occurs may be influenced by several factors. The aim of the experiment is to investigate the effects of different temperatures on the rate of respiration in yeast. ...read more.


Temperature of Yeast/ Glucose solution (degrees C) Number of bubbles given off over 10 minuets 0�C 0 22�C 5 40�C 75 60�C 25 90�C 0 The results indicate that no carbon dioxide gas bubbles were observed when the glucose and yeast mixture was suspended at temperatures of 0�C and 90�C. The highest number of bubbles, 75 in total, over a ten minuet period were seen to be produced by the yeast and glucose sample that had been regulated at 40�C. When the yeast solution was maintained at 22�C it was observed that 5 bubbles of carbon dioxide gas were evolved into the limewater. At a temperature of 60�C the yeast mixture managed to produce 25 bubbles in the ten-minuet period. A graph of the results from the experiment was constructed and a copy has been included on the following page Conclusion The main aim of the experiment was to perform a simple test at a variety of temperatures in order to observe any changes in the yeast sample respiration rate. The temperature of the test solution that evolved the highest number of bubbles was to be considered the optimum temperature for respiration to occur in Saccharomyces Cerevisiae, brewer's yeast. ...read more.


At this point the changed active site would no longer be able to accommodate its unique substrate and the enzyme would cease to function and become denatured. If the enzymes could not function processes, such as respiration that require them, could not occur. The results from the experiment support this theory as the rate of respiration within the yeast samples declined as the temperature rose above 40�C. It is assumed that too many enzymes had become denatured above 40�C to allow the yeast to continue to anaerobically respire. When temperatures fall too far below the optimum allowance, enzymes also struggle to function as the amount of activation energy required to initiate reactions is too great. At cooler temperatures molecules circulate much more slowly leading to a reduced rate in collisions between the active sites and the substrates, producing overall fewer enzymatic reactions. The evidence obtained from the yeast study supports this theory as no bubbles of carbon dioxide were observed at 0�C, suggesting a reduction in respiration due to a fall in enzyme activity. In conclusion the results from the experiment have shown that the optimum temperature required for successful respiration in Saccharomyces Cerevisiae, brewer's yeast, is approximately 40�C. If temperatures deviate much from this optimum point on the thermometer, it may be assumed that fewer essential enzymatic reactions will occur and that the overall rate of respiration will reduce. ...read more.

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