1. INTRODUCTION
11
tures and their relationship to metabolism and, most recently, by the
resynthesis of metabolic systems from their elements (enzymes and
substrates), and the development of the idea that biological form and
function are based upon physicochemical dynamics.
Many biologically occurring compounds, for example, ethanol, sucrose, acetic acid, tartaric acid, and urea, were known in a relatively
pure state before the advent of atomic theory in 1808. But, although
organic chemistry was then "the chemistry of plant and animal substances or bodies which are formed under the influence of the vital
force" (Berzelius, 1827), it was not possible to classify such substances
(except grossly according to radicals, types and copulae) until the
quantitative techniques initiated by Lavoisier, the analytical methods of
Gay-Lussac, Thenard, Berzelius, and Liebig, and the valence theory of
Frankland, Loschmidt, Kekule, and Couper had given rise to the
relatively simple but essentially modern structural theory which appeared
in the decade 1850-1860. Then organic chemistry became the more
general chemistry of the compounds of carbon (Kekule, 1861), and it
rapidly became evident that most of the substances which occur in the
organisms comprising the phylogenetic scale fall into a few well-defined
structural classes: fatty acids and lipids, amino acids and proteins,
saccharides and polysaccharides, nucleotides and nucleic acids. The
recognition that such natural structural classes exist was largely complete before the end of the nineteenth century, and was undoubtedly the
chemical starting-point of systematic comparative biochemistry.
During the period that structural theory was developed and applied
to biologically occurring substances, it was also recognized that life is
associated with catalytic processes. Of course, alcoholic, putrefactive,
and acetic fermentations were known since ancient times, but it was not
until Pasteur's work that such processes were unequivocally connected
with the metabolism of living organisms. In that same era, several
"albuminous substances which possessed the power of producing catalytic reactions'' (3) were discovered: amylase, emulsin, pepsin, and
trypsin. Some controversy arose over the relationship between ferments
which acted only as a part of living cells (organized ferments) and
those which could act in the absence of such cells (unorganized ferments), called enzymes by Kühne (1878), but this controversy was
resolved by Biichner's discovery that "zymase" could be separated from
yeast cells. By 1901, Oppenheimer was able to define enzymes as "ferments produced by the living cell and adhering more or less firmly to
them without having their activities bound up with the vital process
as such" in spite of the fact that "we are still absolutely in the dark as
to the chemical nature of ferments" (5). Furthermore—a fundamental
11
tures and their relationship to metabolism and, most recently, by the
resynthesis of metabolic systems from their elements (enzymes and
substrates), and the development of the idea that biological form and
function are based upon physicochemical dynamics.
Many biologically occurring compounds, for example, ethanol, sucrose, acetic acid, tartaric acid, and urea, were known in a relatively
pure state before the advent of atomic theory in 1808. But, although
organic chemistry was then "the chemistry of plant and animal substances or bodies which are formed under the influence of the vital
force" (Berzelius, 1827), it was not possible to classify such substances
(except grossly according to radicals, types and copulae) until the
quantitative techniques initiated by Lavoisier, the analytical methods of
Gay-Lussac, Thenard, Berzelius, and Liebig, and the valence theory of
Frankland, Loschmidt, Kekule, and Couper had given rise to the
relatively simple but essentially modern structural theory which appeared
in the decade 1850-1860. Then organic chemistry became the more
general chemistry of the compounds of carbon (Kekule, 1861), and it
rapidly became evident that most of the substances which occur in the
organisms comprising the phylogenetic scale fall into a few well-defined
structural classes: fatty acids and lipids, amino acids and proteins,
saccharides and polysaccharides, nucleotides and nucleic acids. The
recognition that such natural structural classes exist was largely complete before the end of the nineteenth century, and was undoubtedly the
chemical starting-point of systematic comparative biochemistry.
During the period that structural theory was developed and applied
to biologically occurring substances, it was also recognized that life is
associated with catalytic processes. Of course, alcoholic, putrefactive,
and acetic fermentations were known since ancient times, but it was not
until Pasteur's work that such processes were unequivocally connected
with the metabolism of living organisms. In that same era, several
"albuminous substances which possessed the power of producing catalytic reactions'' (3) were discovered: amylase, emulsin, pepsin, and
trypsin. Some controversy arose over the relationship between ferments
which acted only as a part of living cells (organized ferments) and
those which could act in the absence of such cells (unorganized ferments), called enzymes by Kühne (1878), but this controversy was
resolved by Biichner's discovery that "zymase" could be separated from
yeast cells. By 1901, Oppenheimer was able to define enzymes as "ferments produced by the living cell and adhering more or less firmly to
them without having their activities bound up with the vital process
as such" in spite of the fact that "we are still absolutely in the dark as
to the chemical nature of ferments" (5). Furthermore—a fundamental