CHAPTER 4 - CARBON AND THE MOLECULAR DIVERSITY OF LIFE
A. The Importance of Carbon
Although cells are 70-95% water, the rest consists mostly of carbon-based compounds.
Proteins, DNA, carbohydrates, and other molecules that distinguish living matter from inorganic
material are all composed of carbon atoms bonded to each other and to atoms of other elements.
These other elements commonly include hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), and
1. Organic chemistry is the study of carbon compounds
The study of carbon compounds,
, focuses on any compound with carbon (organic
While the name, organic compounds, implies that these compounds can only come from
biological processes, they can be synthesized by non-living reactions.
Organic compounds can range from simple molecules, such as CO
molecules, like proteins, that may weigh over 100,000 daltons.
The overall percentages of the major elements of life (C, H, O, N, S, and P) are quite uniform from
one organism to another.
However, because of carbon’s versatility, these few elements can be combined to build an
inexhaustible variety of organic molecules.
While the percentages of major elements do not differ within or among species, variations in organic
molecules can distinguish even between individuals of a single species.
The science of organic chemistry began in attempts to purify and improve the yield of products from
Later chemists learned to synthesize simple compounds in the laboratory, but they had no
success with more complex compounds.
The Swedish chemist Jons Jacob Berzelius was the first to make a distinction between organic
compounds that seemed to arise only in living organisms and inorganic compounds from the
This led early organic chemists to propose
, the belief in a life outside the limits of physical
and chemical laws.
Support for vitalism began to wane as organic chemists learned to synthesize more complex organic
compounds in the laboratory.
In the early 1800s the German chemist Friedrich Wöhler and his students were able to synthesize
urea from totally inorganic starting materials.
In 1953, Stanley Miller at the University of Chicago was able to simulate chemical conditions on the
primitive Earth to demonstrate the spontaneous synthesis of organic compounds.
Organic chemists finally rejected vitalism and embraced