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BL1410 Respiration Lab Protocol and questions .pdf - BL1410...

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BL1410 Principles of Biology, Michigan Technological UniversityLaboratory Protocol1Name: ______________________________Section (table): _______________________Respiration and FermentationBackgroundAs we learned in lecture and in a previous lab, photosynthesis is the process by which lightenergy is used to fix carbon dioxide (CO2) into sugar. Organisms that use inorganic sources ofcarbon areautotrophsAutotrophs that perform photosynthesis get their energy from light, andin the process make organic materials such as carbohydrates, are calledphotoautotrophs.Heterotrophs areother organisms that are unable to fixinorganic carbonsuch as CO2and thusget their carbon and their energy (formation of ATP) from breaking the bonds in theorganicmattermade by the autotrophs. This process is part of cellularrespiration. The overall chemicalequation for complete aerobic respiration is:6𝑂𝑂2+𝐢𝐢6𝐻𝐻12𝑂𝑂6β†’6𝐢𝐢𝑂𝑂2+ 6𝐻𝐻2𝑂𝑂+ ATPHowever, if oxygen is not available, some organisms can still make use of the substrates such assugars byanaerobic respiration.For example, many organisms can aerobically metabolizesugars (simple carbohydrates) but if they are in an anaerobic environment they can undergofermentation of the sugars (actually the Pyruvates produced by glycolysis).Yeast(Saccharomyces cerevisiae) can undergo alcohol fermentation in which they convert pyruvatesinto acetaldehyde) and then to ethanol, CO2and some energy. The simple equation for this isshown below:If the sugar is glucose then𝐢𝐢6𝐻𝐻12𝑂𝑂6β†’2𝐢𝐢2𝐻𝐻5𝑂𝑂𝐻𝐻+ 2𝐢𝐢𝑂𝑂2+ ATPHowever, not all sugars are the same with regard to the ability of yeast to metabolize them (breakthem down) and use them as an energy source.In addition, the breakdown product (ethanol)slows the fermentation process as the concentration increases because yeast growth is inhibitedby ethanol concentrations (Stanley et al. 2010)ObjectivesIn this lab you will do two exercises to measure aspects of yeast metabolism.In part A you willexamine the pattern of production of CO2and assess the consumption of O2by yeast whenexposed to different substrates (sugars).For these measurements you will use CO2and O2sensors to measure the amount of each gas in the headspace of your solutions.In part B you willmeasure gas displacement as an indicator of the amount of CO2produced when yeast are exposedto different levels of ethanol and incubated in fermentation tubes.
BL1410 Principles of Biology, Michigan Technological UniversityLaboratory Protocol2Chemicals Used●Ethanol●Sucrose●Fructose●Glucose (Dextrose)●LactoseSafety Precautions for the Laboratory1.Safety goggles must be worn while pouring and working with chemicals.2.Ethanol is highly volatile, flammable, and should be kept sealed whenever possible.

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Glucose, Michigan Technological University, laboratory protocol

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