Biochemistry and Molecular Biology - Belyasova N.A. 2002

Introduction
A Brief Historical Outline of the Development of Biochemistry and Molecular Biology

As an independent science, biochemistry emerged by the mid-19th century, although the foundations for its development were laid almost a century earlier. These include J. Priestley's discovery (1770–1780) of oxygen absorption by animals and release by plants; the Isolation of the first organic molecules from natural sources—glycerol, malic, citric, lactic, and uric acids (Scheele, Rouelle, 1770–1786); the elucidation of protein composition as nitrogen-containing substances (Dalton, 1803); the isolation of the first amino acid, asparagine, from asparagus (Asparagus) juice (Vauquelin, 1806); the formulation of the equation for Alcoholic Fermentation (Gay-Lussac, 1810); and the ISOLATION OF A crystalline fatty acid preparation along with the discovery of Cholesterol during the acid Treatment of soap (Chevreul, 1811, 1812).

Finally, in 1828, F. Wöhler synthesized the first organic compound—urea—from inorganic substances, thereby delivering a crushing blow to vitalism. Many consider this achievement to be the primary milestone in the establishment of biochemistry as an independent science. In 1833, Payen and Persoz purified and studied The properties of the first enzyme molecule, wheat amylase, postulating The Central Role of Enzymes in biology. Between 1854 and 1864, Pasteur proved that fermentation is a function of living Cells (Yeast) and provided decisive arguments against the hypothesis of spontaneous generation. Concurrently, beginning with F. Miescher's Discovery of DNA (1869), the Chemistry of Nucleic Acids was born.

By the end of the 19th century, a fierce debate erupted between Louis Pasteur and J. Liebig regarding The Nature of fermentation. Pasteur maintained that fermentation was a phenomenon that could occur exclusively within living microbial cells, whereas Liebig held a different view, emphasizing the Chemical Nature of the process involving substances similar to the already known amylase. The controversy was resolved by the Buchner brothers, who demonstrated in 1897 that fermentation could take place in Cell-free yeast extracts. Thus, it became clear that fermentation is a chemical process capable of occurring both within and outside cells, driven by enzymes—the metabolic products of living organisms. As historians put it: «...the appearance of gas bubbles in the Buchners' experiment marked the birth of modern biochemistry and enzymology.»

Following this discovery, biochemistry received a powerful developmental impetus: in 1901–1902, Emil Fischer showed that Proteins are Polypeptides and established the Nature of the peptide bond; in 1905, Knoop discovered fatty acid β-oxidation; in 1911, Funk isolated crystalline thiamine and proposed the term «vitamin»; in 1913, Michaelis and Menten developed the THEORETICAL FOUNDATIONS OF enzyme kinetics; in 1926, Sumner isolated crystalline urease and proved it to be a protein; in 1933, Krebs and Henseleit discovered and elucidated the Chemistry of the Urea Cycle, while Embden and Meyerhof identified the most critical features of Glycolysis and fermentation processes. Even this modest Overview of key biochemical milestones from the first half of the 20th century demonstrates that scientific interest had shifted toward decoding the processes operating within the living cell.

Consequently, by the mid-20th century, the Major Metabolic Pathways of substances within cells had been elucidated. These breakthroughs included the discovery of Photosynthesis (K.A. Timiryazev), The Tricarboxylic Acid Cycle (H. Krebs), The process of Oxidative Phosphorylation, and the principles of cellular energy conversion.

During this period, biochemists were still unable to answer one of humanity's most pressing questions: which cellular substance carries hereditary information. Proteins had been studied more thoroughly than other macromolecules, revealing a startling diversity. It seemed logical to assume that protein molecules, owing to their compositional Variability, served as the material encoding the equally diverse traits of living organisms. However, as early as 1928, Griffith's experiments provided the first hints that Nucleic Acids played a role in this process. Then, in 1944, American researchers Avery, MacLeod, and McCarty proved that DNA is the substance responsible for storing and transmitting hereditary information in cellular organisms.

The investigation of nucleic acid Structure enlisted the most advanced Methods available to researchers across various scientific disciplines. In particular, X-ray crystallography, the foundations of which were laid in 1934 by Bernal and Crowfoot, enabled scientists to approach the three-dimensional structure of DNA. Around this time, molecular biology emerged as an independent science. Its inception was first mentioned by Warren Weaver, Director for the Natural Sciences at the Rockefeller Foundation. In his 1938 report, he noted that «in the borderland areas where physics and chemistry meet biology, a new branch of science is gradually emerging—molecular biology—which is beginning to lift the veil on many of the mysteries surrounding the fundamental elements of the living cell.»

Modern biochemistry is distinguished by the integration of rapid automated methods into the analysis of substances and processes. Today, automated control is applied to amino acid protein analysis, the Quantitative determination of mono- and Disaccharides in biological fluids, nucleic acid sequencing, peptide and oligonucleotide synthesis, as well as the chromatographic and gel-filtration Separation of natural compounds, among others.

Concluding this overview of biochemical achievements, one can state that biochemistry investigates the chemical Composition and Structure of living matter, as well as the chemical processes occurring within living organisms.

The birthdate of molecular biology is generally considered to be 1953, when physicist Francis Crick and biologist James Watson deciphered The structure of DNA—The Double Helix. This remarkable discovery formed The basis of most molecular biological research, underpinned by the aforementioned achievements of the «phage group» (Avery et al.) and physicists (Bernal, Crowfoot). Furthermore, the shift in biochemists' focus toward nucleic acids was facilitated by Beadle and Tatum's 1941 postulation of the «one Gene–one enzyme» principle, which they formulated while studying biochemical Mutations in the bread mold Neurospora crassa.

A defining feature of molecular biology is the investigation of macromolecular structure and its relationship to function. This is most vividly demonstrated in the case of DNA. However, molecular biology also explores other molecules, as evidenced by the major achievements of the field: the structure of several proteins has been deciphered and linked to their biological Functions (M. Perutz, J. Kendrew, F. Sanger, C. Anfinsen, et al.); the structure and mechanisms of Nucleic Acids and Ribosomes have been elucidated (J. Watson, F. Crick, T. Caspersson, J. Brachet, S. Weiss, et al.); METABOLISM/28.html">The Genetic Code has been cracked (M. Nirenberg, H. Khorana, S. Ochoa); a method for the Specific Cleavage of DNA using Restriction Endonucleases—the foundation of modern Introduction/32.html">Genetic Engineering—has been developed (H. Smith, W. Arber, D. Nathans); The phenomenon of reverse Transcription has been discovered (H. Temin, D. Baltimore, S.M. Gershenzon); the mechanisms and stages of PROTEIN AND NUCLEIC acid Biosynthesis have been uncovered (F. Jacob, J. Monod, F. Crick; A. Kornberg, S. Ochoa); viral structures and reproduction mechanisms have been established, along with genetic engineering techniques (P. Berg, W. Arber, H. Smith); methods for introducing foreign DNA into various cells via vectors have been developed (H. Boyer, S. Cohen, D. Helinski); gene synthesis has been achieved (H. Khorana); the virogenetic theory of Cancer origin has been proposed (L.A. Zilber); The nucleotide sequence of tRNA has been determined (A.A. Bayev); and a DNA Sequencing method has been devised (A. Maxam, W. Gilbert, F. Sanger).

Thus, molecular biology can be defined as the science that studies the functioning of living organisms through the prism of the Chemical Structure of the molecules and atoms that compose them.