An element found in gas form which is essential for life

In air it is found combined with another oxygen atom indicated by the symbol O2. It represents approximately 21% of the earth’s atmosphere.  It combines with hydrogen and forms water with chemical composition of H2O. Two hydrogen atoms combined with one oxygen atom.

Oxygen is required for combustion.  In cells it is required for aerobic cellular respiration to produce energy. Aerobic cellular metabolism is the primary form of energy creation in a cell.

In the atmosphere, the amount of gas present can be expressed as the partial pressure that the gas exerts of the total pressure. For example at sea level the atmospheric pressure is approximately 760 mmHg. Oxygen is 21% of the atmosphere and its partial pressure is approximately160 mmHg

The partial pressure of oxygen is expressed as pO2.  At sea level the pO2  would be expressed pO= 160 mmHg or 160 Torr.

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