Biochemistry, or biological chemistry, is the branch of chemistry that studies the complex chemical reactions that give rise to life: the structure and transformations of the components of cells, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules.
Although there are a large number of different biomolecules, they are all essentially composed of the same basic building blocks (generically called monomers) arranged in different orders. Each class of biomolecules has a number of different subunits.
The biochemistry of cellular metabolism and the endocrine system has been extensively described. Other areas of biochemistry include the study of the genetic code (DNA, RNA), protein synthesis, cell membrane transport mechanisms, and signal transduction.
In terms of speculative orientation and methodological criteria, biochemistry is one of the most modern branches of the biological sciences, and its progress has been of great benefit to mankind, allowing it to achieve scientific results of sometimes incalculable importance. In the field of medicine, biochemistry has given a modern face to physiology and pathology, radically changing the concept of disease. It has led to the observation that, in various morbid states, the alteration of structures is merely the consequence of general or localized biochemical disturbances; the anatomo-pathological criterion is thus insufficient to explain the origin and evolution of diseases or to indicate appropriate systems of treatment. The development of physiological biochemistry has led to the parallel development of animal and plant pathological biochemistry, to which are linked the latest findings on metabolic, proliferative and degenerative diseases and on the molecular basis of some diseases of the blood, nervous and endocrine systems. In the last decade of the 20th century, studies on the structure of biological macromolecules have developed strongly.
The chemistry of living organisms, after uncertain beginnings in the 18th century, gained credibility and acceptance with the synthesis of urea in the laboratory, carried out by Wohler in 1828. This experiment was important not only for its intrinsic value, but also because it demonstrated the continuity between the chemistry of living and inanimate matter, and because it continued a line of research of incalculable importance initiated by Lavoisier, namely the study of the intermediate and final products of metabolism.
In little more than a century, the intermediate and final metabolites of a large number of metabolic cycles have been identified: glycolysis, the pentose phosphate pathway, the Krebs cycle, the urea cycle, the Calvin cycle, and others. This extraordinary achievement of classical biochemistry has had tremendous spin-offs and applications in medicine, elucidating pathogenetic mechanisms and suggesting possible therapies for a large number of metabolic diseases, both inherited and acquired, including diabetes mellitus, gout, phenylketonuria, porphyrias, and many others.
Not only are all the major biochemical constituents of cells now known, but also their mechanisms of synthesis and degradation, and research in this field is directed toward delving into their details or investigating less fundamental metabolic pathways; not unreasonably, the Calvin cycle, elucidated after more than a decade of research beginning in 1945, has been called the last of the great metabolic pathways.
Another line of research in classical biochemistry, the study of the structure and function of biological macromolecules: proteins, nucleic acids, and polysaccharides, for many of which the chemical and stereochemical structures are known with great precision, down to the resolution of the spatial position of individual constituent atoms, has enjoyed comparable success. This line of research has also had invaluable spin-offs in biology and medicine.
Classical biochemistry seems to have exhausted its main field of application, and modern research is moving in new directions aimed at integrating the achievements of the discipline with those of neighboring disciplines such as cell biology, anatomy, and physiology: consequently, in outlining the current lines of development of biochemistry, one cannot fail to note its confluence with those of other disciplines, a confluence that has not infrequently given rise to entirely new disciplines such as molecular biology and biophysics.
The main lines of modern biochemistry include bioenergetics, the study of the regulatory mechanisms of cellular functions, the structure of cellular organelles and whole viral microorganisms, neurochemistry and the mechanism of synaptic excitation. These phenomena have in common that they depend on the precise spatial relationships established between the macromolecules involved, which could never be reproduced in solutions of purified components: they require and construct a structure that could rightly be called “microanatomical”, if microanatomy were not that of microanatomy, a term already used with a different meaning.