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  2. Oxygen cycle - Wikipedia

    en.wikipedia.org/wiki/Oxygen_cycle

    The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O 2), as it is a common product or reactant of many biogeochemical redox reactions within the cycle. [2] Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O 2 ...

  3. Marine biogeochemical cycles - Wikipedia

    en.wikipedia.org/wiki/Marine_biogeochemical_cycles

    The word oxygen in the literature typically refers to molecular oxygen (O 2) since it is the common product or reactant of many biogeochemical redox reactions within the cycle. [37] Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O 2 production) or sink (O 2 consumption). [36 ...

  4. Oxygen evolution - Wikipedia

    en.wikipedia.org/wiki/Oxygen_evolution

    Oxygen evolution is the chemical process of generating elemental diatomic oxygen (O 2) by a chemical reaction, usually from water, the most abundant oxide compound in the universe. Oxygen evolution on Earth is effected by biotic oxygenic photosynthesis , photodissociation , hydroelectrolysis , and thermal decomposition of various oxides and ...

  5. Biogeochemical cycle - Wikipedia

    en.wikipedia.org/wiki/Biogeochemical_cycle

    The six aforementioned elements are used by organisms in a variety of ways. Hydrogen and oxygen are found in water and organic molecules, both of which are essential to life. Carbon is found in all organic molecules, whereas nitrogen is an important component of nucleic acids and proteins.

  6. Geological history of oxygen - Wikipedia

    en.wikipedia.org/wiki/Geological_history_of_oxygen

    Early fluctuations in oxygen concentration had little direct effect on life, with mass extinctions not observed until around the start of the Cambrian period, 7] The presence of O 2 provided life with new opportunities. Aerobic metabolism is more efficient than anaerobic pathways, and the presence of oxygen created new possibilities for life to ...

  7. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. ... that are important to (or generated by) life. Oxygen reacts ...

  8. Cellular respiration - Wikipedia

    en.wikipedia.org/wiki/Cellular_respiration

    The citric acid cycle is also called the Krebs cycle or the tricarboxylic acid cycle. When oxygen is present, acetyl-CoA is produced from the pyruvate molecules created from glycolysis. Once acetyl-CoA is formed, aerobic or anaerobic respiration can occur. When oxygen is present, the mitochondria will undergo aerobic respiration which leads to ...

  9. Ecosystem respiration - Wikipedia

    en.wikipedia.org/wiki/Ecosystem_respiration

    This constant cycle of carbon through the system is not the only element being transferred. In animal and plant respiration these living beings take in glucose and oxygen while emitting energy, carbon dioxide, and water as waste. These constant cycles provide for a influx of oxygen into the system and carbon out of the system.