Ask A Scientist Chemistry Archive

name         Chelsea
status       student
age          12

Qestion -   Why is there so much carbon in the body
Among all of the chemical elements, carbon has the greatest capacity to
bond to itself and to most other nonmetallic elements, expecially nitrogen,
phosphorus, oxygen, sulfur, and hydrogen. This ability makes it the building
block of life as we know it. And this is why our bodies, and other animal
and plant life are composed predominantly of carbon.

Vince Calder
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At first glance, it may be surprising that carbon is abundant in living
organisms when it is not so abundant in the Earth's crust. (Here is a site I
found on the percentages of elements on the Earth's
crusthttp://chemistry.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=chemistry
&zu=http%3A%2F%2Fww2.wpunj.edu%2Fcos%2Fenvsci-geo%2Fdistrib_resource.htm).

However, most of the elements on the top of this list, either make fewer
bonds than carbon (oxygen at the top of the list makes only two bonds
whereas carbon makes four), make a lot stronger bonds than carbon (silicon
makes four bonds also, but they tend to be stronger), or are trapped in
minerals that make them difficult to extract (aluminum and iron oxides are
very stable and tend to remain in that form). Thus, one can surmise that
life that used carbon as its basic building material is successful because
it can have many types of reactions (due to the four-bond capability) and by
the fact that carbon-carbon bonds are relatively weaker (thus, they can be
easily broken and reformed - producing a faster reacting system).

Greg (R. Gregorius)
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