Biochemistry: The chemistry of biology, the application of the tools and concepts of chemistry to living systems.
Biochemists study such things as the structures and physical properties of biological molecules, including proteins, carbohydrates, lipids, and nucleic acids; the mechanisms of enzyme action; the chemical regulation of metabolism; the chemistry of nutrition; the molecular basis of genetics (inheritance); the chemistry of vitamins; energy utilization in the cell; and the chemistry of the immune response.
Fields closely related to biochemistry include biophysics, cell biology, and molecular biology. Biophysics applies to biology the techniques of physics. Cell biology is concerned with the organization and functioning of the individual cell. Molecular biology, a term first used in 1950, It overlaps biochemistry and is principally concerned with the molecular level of organization.
Modern chemistry: Antoine-Laurent Lavoisier (1743-1794), the father of modern chemistry, carried out fundamental studies on chemical oxidation and showed the similarity between chemical oxidation and the respiratory process.
Organic chemistry: In the 19th century, Justus von Liebig studied chemistry in Paris and carried the inspiration gained by contact with the former students and colleagues of Lavoisier back to Germany where he put organic chemistry on a firm footing.
Enzymes: Louis Pasteur proved that various yeasts and bacteria were responsible for "ferments," substances that caused fermentation and, in some cases, disease. He also demonstrated the usefulness of chemical methods in studying these tiny organisms and was the founder of what came to be called bacteriology. Later, in 1877 Pasteur's ferments were designated as enzymes.
Proteins: The chemical nature of enzymes remained obscure until 1926,when the first pure crystalline enzyme (urease) was isolated. This enzyme and all others proved to be proteins, which had already been recognized as high-molecular-weight chains of amino acids which we now know are the building blocks of protein.
Vitamins: The mystery of how minute amounts of dietary substances prevent diseases such as beriberi, scurvy, and pellagra came clear in 1935 when riboflavin (vitamin B2) was found to be an integral part of an enzyme.
ATP: In 1929 the substance adenosine triphosphate (ATP) was isolated from muscle. The production of ATP was found associated with respiratory (oxidative) processes in the cell and in 1940 ATP was recognized by F.A. Lipmann as the common form of energy exchange in cells.
Radioisotopes: The use of radioactive isotopes of chemical elements to trace the pathway of substances in the body was initiated in 1935 by R. Schoenheimer and D. Rittenberg, providing an important tool for investigating the chemical changes that occur in cells.
DNA: In 1869 a substance was isolated from the nuclei of pus cells and was called nucleic acid, which later proved to be deoxyribonucleic acid (DNA). It was not until 1944 that the significance of DNA as genetic material was revealed, when bacterial DNA was shown to change the genetic matter of other bacterial cells. Within a decade, the double helix structure of DNA was proposed by Watson and Crick, providing an understanding of how DNA functions as the genetic material.