Eli5: What’s so special with oxygen that every living being users it and not other gas?
In: Biology
It can react with carbon and hydrogen to give energy, and os incredibly abundant. Nothing would evolve to breathe/use nitrogen because it is mostly unreactive and nothing would evolve to use fluorine because it is super uncommon.
Not every living being does use it, plenty of microbes are anerobic. As for what’s special about it, it releases a lot of energy when reacted with hydrocarbons, and it’s ubiquitous enough that being dependent on it is worth the advantage in energy extraction, at least for larger organisms.
Fluorine is too reactive (everything), nitrogen is too inert (needs a lightning bolt to change from its gas form). Plenty of things ‘breath’ nitrogen, but they’re pretty small. Oxygen is happy as a gas, but will react with minimal energy input. It’s just how the valence electrons worked out, if it was any other way, something else would have evolved. Phosphorus is a fun mental exercise!
Oxygen is special in that its a powerful oxidizer that can take up electrons so that the energy making mechanisms in our cells can keep functioning. Our energy making mechanism is just a game of hot potato with electrons that makes a little bit of energy for the cell with each throw. Oxygen removes the electron when its cooled down so that a new electron can take its place. That combined with its ability to form water and its abundance in the atmosphere make it an ideal candidate
There are organisms deep in the ocean (where there is little oxygen) that use sulfur in place of oxygen. Sulfur is right below Oxygen in the periodic table, so it has similar properties. Its more abundant than oxygen in this area due to volcanic vents, so organisms evolved to use it instead
It’s very common on our planet’s surface and it reacts very strongly.
The electrons of the atoms are arranged so that it really wants to take more electrons.
It’s really common because some early life spat it out as a byproduct of making food. Which was a problem for them since it was also poisonous to them. This was 2.4 billion years ago, and is called the Oxygen Catastrophe and it nearly wiped out all life.
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