Why carbon?
In: Biology
Isaac Arthur has [a great video about non-Carbon based life](https://www.youtube.com/watch?v=Y584AjZmqwY) that indirectly discusses this topic, but in short most of the molecules used by the life functions of Earth’s species are based around carbon atoms. This is why we aren’t simply referred to as “water-based life”, because sugars, enzymes and other molecules associated with life functions are not based around water molecules, even though water makes up the majority of our bodies.
The carbon atom is very versatile, as it has four electrons in its outer shell. That means it needs to borrow four electrons to have a full outer shell, which is something atoms like. This, in turn, means carbon can create strong bonds to other carbon atoms, creating rings or chains of carbon and other elements. These rings and chains can fold in different ways, creating an enormous variation.
The upshot is that the chemistry of carbon compounds is really complex and that is essentially what life is: complex chemistry.
In summary, we need complex chemistry to be alive, and the properties of carbon makes complex chemistry possible. There may be life based on elements similar to carbon – for example silicon – but all life on earth is based on carbon.
Chemical elements are defined by their number of protons. 1 proton= hydrogen, 2= helium, etc. Each element, barring being electrically charged (ionized), has an equal number of electrons. Carbon is element 6, and has 6 electrons,which gives it unique chemical properties.
Carbon is able to bond to other carbon atoms while also bonding with other elements. This is an amazingly versatile ability, which allows it to make INSANELY complex chain molecules. It can do this while having ranging bond strengths as well, having single or double electron bonds with itself or other elements, making for endless combinations possible.
Other elements in carbons group are somewhat capable of this , as they also have 6 electrons in their outer shell. Silicon is the only one other such element which can form any kind of stable bond chain, but the energies required are far too much to be feasible for life (as we know it)
So we are carbon based life because our DNA, proteins, hormones, everything related to life has a backbone of carbon.
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