Oxygen cycle

Oxygen cycle scale.

The oxygen cycle is the chain of reactions and processes that describe the circulation of oxygen in the terrestrial biosphere.

By breathing, animals and humans take in the dioxygen, O₂ that plants produce, from the air and then we exhale carbon dioxide. Plants, in turn, take the carbon dioxide that animals and humans exhale, to use it in the process of photosynthesis. Plants and photosynthesizers such as diatoms are the only ones capable of converting carbon dioxide (CO₂) into oxygen.

In cellular respiration, oxygen is reduced for the production of energy, generating carbon dioxide, and in the process of photosynthesis, oxygen and glucose are produced from water, carbon dioxide (CO₂) and solar radiation.

It should be said that water is also formed in the oxygen cycle, since the human body expels water vapor (H₂O) when exhaling.

When a heterotrophic being dies, thanks to decomposers, a small amount of oxygen (O₂) is released.

Atmosphere

O₂ gives the atmosphere an oxidizing character. It was formed by photolysis of H2O, forming H2 and O2:

H₂O + hν → H₂ + 1/2O₂

Molecular oxygen present in the atmosphere and dissolved in water is involved in many reactions of living beings. In cellular respiration, dioxygen is reduced for the production of energy, generating carbon dioxide, and in the process of photosynthesis, oxygen and glucose are produced from water, carbon dioxide (CO2) and solar radiation.

Hydrosphere and atmosphere

Oxygen is slightly soluble in water, its solubility decreasing with temperature. It conditions the redox properties of aquatic systems. It oxidizes bioorganic matter giving carbon dioxide and water.

Carbon dioxide is slightly soluble in water giving carbonates; conditions the acid-base properties of aquatic systems. An important part of the [[dioxide