Lab 7 - Biology 05LA Winter Qtr. 2008 Lab 7 page 1 LAB #7:...

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Biology 05LA – Winter Qtr. 2008 Lab 7 – page 1 LAB #7: FERMENTATION AND RESPIRATION All living organisms must continuously expend energy to maintain themselves and drive energy- requiring life processes. This energy is ultimately derived from the sun via photosynthesis. Because not all organisms are photosynthetic and the sun does not always shine, organisms need alternative sources of energy. Plants provide this energy in the form of organic molecules that contain large amounts of chemical potential energy. These molecules (e.g. sugars) are relatively stable and can be stored or transported. This energy is extracted by a stepwise, enzymatically-mediated oxidation of these molecules that results in the production of another energy-storing molecule, adenosine triphosphate (ATP). When the terminal phosphate is split off ATP, the ATP is converted to ADP (adenosine diphosphate) and considerable energy is made available for “cellular work”. The ADP is then available for the regeneration of more ATP. Shown below are balanced summary equations for two classes of metabolism that provide most of the ATP that cells use. C 6 H 12 O 6 (glucose) + 2 ADP + 2 Pi 2 CH 3 CH 2 OH (ethanol) + 2 CO 2 + 2 ATP + heat Alcoholic Fermentation C 6 H 12 O 6 + 6 O 2 + 36* ADP + 36 Pi* 6 CO 2 + 6 H 2 O + 36 ATP* + heat Cellular Respiration *As reported in your text, this value can be as high as 38 under ideal conditions. The experiments we will perform in this exercise are made possible by two features related to the above equations. The first is that gaseous reactants and/or products are characteristic of both metabolic processes. The second is that it is relatively easy to determine number of moles of a gas in a confined space with a device known as a manometer. This determination involves the measurement of the volume occupied by the gas of interest and then relating this volume to the number of moles of that gas. This relationship can be made via the combined gas law (PV = nRT) where P = pressure, V = volume, n = number moles of a gas, R = the gas constant, and T = temperature. Another important feature of these equations is that they are in stoichiometric balance. This allows us to calculate the amount of any reactant or product if the amount of any other reactant or product is known. In our experiments, we will measure the rate of CO 2 production in yeast cells undergoing alcoholic fermentation and the rate of O 2 consumption by corn seedlings undergoing cellular respiration. Once these rates are determined, the stoichiometric relationships of the reactions will be used to calculate the rates of ATP production for the organisms. The rate of ATP production is important because it closely approximates an organism’s rate of energy utilization. This physiological parameter is termed metabolic rate. The reason that the rate of ATP production is so closely related to metabolic rate is because ATP is not stored by cells. Therefore, for it to be produced it must be recycled through the energy-releasing conversion to ADP + Pi.
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This lab report was uploaded on 04/07/2008 for the course BIO 5A taught by Professor Zhu/cardullo/rao during the Winter '08 term at UC Riverside.

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Lab 7 - Biology 05LA Winter Qtr. 2008 Lab 7 page 1 LAB #7:...

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