Oxygen is a chemical element essential for respiration and a key component in water and various chemical processes.Oxygen is an invisible gas that fills our lungs with every breath. It is like a magical elixir of life: without it, fire goes out and fish in water stop breathing. Oxygen is born in the green leaves of plants under the sun, as a gift to us from generous nature.
Oxygen was first isolated by Scheele (1771) and Priestley (1774), but the decisive role was played by Lavoisier (1777), who refuted the phlogiston theory and showed that air consists of two gases: 'vital' (oxygen) and 'asphyxiating' (nitrogen). In 1781, Cavendish synthesized water from hydrogen and oxygen. In the 20th century, the Nobel Prize was awarded to Otto Warburg (1931) for his work on the respiratory enzyme using oxygen.
In mitochondria, oxygen serves as the final electron acceptor in the electron transport chain, being reduced to water. This process, coupled with ATP synthesis, obeys the second law of thermodynamics: the energy of chemical bonds in food is converted into the energy of high-energy phosphate bonds in ATP with heat dissipation. Without oxygen, the cell switches to anaerobic glycolysis, which is 18 times less efficient.
Oxygen is the most abundant element on Earth: it makes up almost half the mass of the Earth's crust and two-thirds of your body's mass. And it is oxygen that colors blood red by combining with iron.












