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is required for the release of energy from food molecules (aerobic respiration). Instead of breaking down food molecules completely, muscle cells switch to a form of partial breakdown that does not require (anaerobic respiration) so that they can continue to gen ....

Middle of Essay
.... and its compounds play a key role in many of the important processes of life and industry. in the biosphere is essential in the processes of respiration and metabolism, the means by which animals derive the energy needed to sustain life. Furthermore, is the most abundant element at the surface of the Earth. In combined form it is found in ores, earth’s, rocks, and gemstones, as well as in all living organisms. is a gaseous chemical element in Group VA of the periodic table. The chemical symbol for atomic is O, its atomic number is 8, and its atomic weight is 15.9994. Elemental is known principally in the gaseous form as the diatomic molecule ....