Respiration160 - Cell Respiration - 1 All cells must do...

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Cell Respiration - 1 All cells must do work to stay alive and maintain their cellular environment. The energy needed for cell work comes from the bonds of ATP. Cells obtain their ATP by oxidizing organic molecules, a process called cellular respiration. Although many organic molecules can be oxidized, glucose, a main product of photosynthesis, is the primary fuel molecule for the cells of living organisms. Every living organism, autotroph and heterotroph, must do cell respiration. In fact, the metabolic pathways used in the process of cellular respiration are the same in virtually all eukaryotic organisms as well as most prokaryotic organisms. Recall that organisms that do photosynthesis (or properly, manufacture their own fuel molecules) are called autotrophs. Heterotrophs obtain their fuel molecules "pre-formed" by other organisms. Animals, fungi and many protists are heterotrophs, as are most bacteria. Plants and some protists are autotrophs, as are some bacteria. Most eukaryotic organisms are aerobic (oxygen requiring). Aerobic cell respiration is required in order to obtain enough energy (ATP) from the oxidations of fuel molecules for these organisms to survive. In aerobic respiration glucose is oxidized to water and carbon dioxide. Oxygen is required as the final electron acceptor for the oxidations. Most organisms are obligate aerobic organisms. C 6 H 12 O 6 + 6O 2 ± 6H 2 O + 6CO 2 + 686 kcal energy (ATP + Heat) Not all cell respiration is aerobic. All organisms do some type of anaerobic respiration during times of oxygen deficit, although it may not be sufficient to sustain the organism's ATP needs for many species. Fuel molecules oxidized without oxygen yield smaller amounts of ATP. The fermentations involve the partial breakdown of glucose without using oxygen. Many prokaryotes have a variety of fermentation pathways, using a number of different fuel molecules. By definition, the end product for the fermentations is an organic molecule. In aerobic cellular respiration, the final electron acceptor is oxygen, hence, the emphasis on oxygen in aerobic cell respiration. In addition, some prokaryotes use anaerobic electron transfer respiration pathways in which their final electron acceptor is an inorganic molecule such as sulfate, iron, or nitrogen compounds. Some organisms are obligate anaerobes. They cannot survive in the presence of oxygen. The Clostridium bacteria that cause botulism poisoning, tetanus and gangrene are obligate anaerobes. Other anaerobes are metabolic anaerobes; they lack the enzymes needed to do aerobic cell respiration. Many of our intestinal bacteria, such as the Lactobacillus bacteria, are metabolic anaerobes. Some organisms will survive nicely in the absence of oxygen but will do aerobic respiration when oxygen is available. Yeast organisms and E. coli are two such facultative organisms.
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Cell Respiration - 2 Aerobic and Anaerobic Respiration Pathways Oxidation-Reduction Reactions in Cell Respiration The oxidations of fuel molecules in aerobic cell respiration use specialized electron
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Respiration160 - Cell Respiration - 1 All cells must do...

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