Carbon is the key elemental building block for
all known terrestrial life. It's commonly assumed in astrobiology that it will also provide the basis for most life elsewhere in the universe.
The reason for this is not only carbon's ability to form a vast range of
large, complicated molecules with itself and other elements, especially hydrogen, oxygen,
and nitrogen, but also its unique facility
for maintaining the right balance of stability and flexibility in molecular
transformations that underlie the dynamic complexity of life. In aqueous
systems at temperatures common on Earth, carbon is so superior to any other
atom as a polymeric unit, that it has come to be the basis for the structure
of biomolecules essential for all basic metabolic processes.
|True or false?
|"Life exists in the universe only because the carbon
atom possesses certain exceptional properties."
– James Jeans, The Mysterious Universe
It may be that we find it hard to see viable alternatives to carbon biochemistry
because we have no experience of such alternatives. Being carbon-based life-forms
ourselves, we may suffer from what's been called carbon chauvinism.
On the other hand, scientists have so far discovered nothing in the chemistry
of other elements to remotely compare with the millions of organic compounds
to which carbon gives rise.
The one possible exception is silicon which
is chemically similar to carbon and an important constituent of many living
cells. See silicon-based life.