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. Test samples of Saccharomyces Cerevisiae, brewer's yeast, shall be mixed with a small amount of glucose and will be maintained at temperatures of 0˚C, 22˚C, 40˚C, 60˚C and 90˚C. Each test tube will then be monitored closely and the number of carbon dioxide gas bubbles given off over a ten-minuet period of time will be recorded in a table. The temperature of the test solution that evolves the highest number of bubbles will be considered the optimum temperature for respiration to occur in yeast.

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Procedure

Figure 1. A Diagram showing the sealed test tube containing a glucose and yeast solution maintained at 40˚C producing carbon dioxide gas bubbles and delivering them into a second test tube containing lime water.

Two test tubes were obtained and one was half filled with limewater, the

other was half filled with a glucose solution and a sample of live yeast. The test tube containing the yeast and glucose solution was then placed into an ice filled beaker until it had cooled ...

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