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CAMPBELL BIOLOGY: CHAPTER 3 NOTES
Overview: Carbon – The Backbone of Biological Molecules
• Although cells are 70–95% water, the rest consists mostly of carbon-based compounds.
• Carbon is unparalleled in its ability to form large, complex, and diverse molecules.
• Carbon accounts for the diversity of biological molecules and has made possible the great diversity of
• 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
Concept 4.1 Organic chemistry is the study of carbon compounds
• The study of carbon compounds, organic chemistry, deals with any compound with carbon (organic
• Organic compounds can range from simple molecules, such as CO2 or CH4, to complex molecules such
as proteins, which may weigh more than 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.
• 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
obtained from other organisms.
• Initially, chemists learned to synthesize simple compounds in the laboratory, but 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 that were found in
the nonliving world.
• This led early organic chemists to propose vitalism, the belief that physical and chemical laws did not
apply to living things.
• Support for vitalism began to wane as organic chemists learned to synthesize 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 materials.