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Cells maintain a complex internal habitat that is highly structured
and controlled. They host a never-ending array of metabolic
reactions that are required for functions such as nutrient
processing, growth, and release of energy. Among the most remarkable
features of cell metabolism are enzymes, specialized proteins that
perform key roles in most of these reactions. Recently, biochemists
clarified the actions of an enzyme called OMP decarboxylase, used to
synthesize a molecule that is found universally in the genetic material of
all organisms and viruses. They found that in the presence of the OMP
enzyme, this reaction happens very rapidly—about 30 times per second.
The chances of the reaction happening without the enzyme would
take so long (78 million years) that it is essentially not a realistic possibility.
It is clear that without this enzyme, life as we know it could never
have evolved. This is but one example of the amazing cellular machinery
that is ultimately responsible for the tremendous diversity in the
earth's life forms. In addition, it shows us that the metabolic activities of
cells often share common patterns. With these themes in mind, this
chapter will cover some of the major unifying characteristics of metabolism,
enzymes, the flow of energy, and the pathways that govern nutrient
processing. Having this background will greatly benefit your understanding
of future topics such as genetics, drug therapy, disinfection,
biotechnology, diseases, and the identification of microorganisms.
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