Biochemistry

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Biochemistry

Biochemistry is the study of the molecular basis of life. The study of biochemistry includes the knowledge of the structure and function of molecules found in the biological world and an understanding of the precise biochemical pathways by which organic molecules are either put together or broken down.

Biochemistry seeks to describe the structure, organization, and functions of living matter in molecular terms. Essentially two factors have contributed to the excitement in the field today and have enhanced the impact of research and advances in biochemistry on other life sciences. Firstly, it is now generally accepted that the physical elements of living matter obey the same fundamental laws that govern all matter, both living and non-living. Therefore, the full potential of modern chemical and physical theory can be brought in to solve certain biological problems. Secondly, incredibly powerful new research techniques, notably those developing from the fields of biophysics and molecular biology , are permitting scientists to ask questions about the basic process of life.

Biochemistry draws on its major themes from many disciplines. For example from organic chemistry , which describes the properties of biomolecules; from biophysics, which applies the techniques of physics to study the structures of biomolecules; from medical research, which increasingly seeks to understand disease states in molecular terms and also from nutrition , microbiology, physiology , cell biology, and genetics .

Origins of and development of biochemistry

Biochemistry draws strength from all of these disciplines but is also a distinct discipline, with its own identity. It is distinctive in its emphasis on the structures and relations of biomolecules, particularly enzymes and biological catalysis; on the elucidation of metabolic pathways and their control; and on the principle that life processes can, at least on the physical level, be understood through the laws of chemistry. It has its origins as a distinct field of study in the early nineteenth century, with the pioneering work of Friedrich Wöhler. Prior to Wöhler's time it was believed that the substance of living matter was somehow quantitatively different from that of nonliving matter and did not behave according to the known laws of physics and chemistry. In 1828 Wöhler showed that urea , a substance of biological origin excreted by humans and many animals as a product of nitrogen metabolism, could be synthesized in the laboratory from the inorganic compound ammonium cyanate. As Wöhler phrased it in a letter to a colleague, "I must tell you that I can prepare urea without requiring a kidney or an animal , either man or dog." This was a shocking statement at the time, for it breached the presumed barrier between the living and the nonliving. Later, in 1897, two German brothers, Eduard and Hans Buchner, found that extracts from broken and thoroughly dead cells from yeast , could nevertheless carry out the entire process of fermentation of sugar into ethanol . This discovery opened the door to analysis of biochemical reactions and processes in vitro (Latin "in glass"), meaning in the test tube rather than in vivo, in living matter. In succeeding decades many other metabolic reactions and reaction pathways were reproduced in vitro, allowing identification of reactants and products and of enzymes, or biological catalysts, that promoted each biochemical reaction.

Until 1926, the structures of enzymes (or "ferments") were thought to be far too complex to be described in chemical terms. But in 1926 J.B. Sumner showed that the protein urease, an enzyme from jack beans, could be crystallized like other organic compounds. Although proteins have large and complex structures, they are also organic compounds and their physical structures can be determined by chemical methods.

Modern biochemistry

Today, the study of biochemistry can be broadly divided into three principal areas: (1) the structural chemistry of the components of living matter and the relationships of biological function to chemical structure; (2) metabolism, the totality of chemical reactions that occur in living matter; and (3) the chemistry of processes and substances that store and transmit biological information. The third area is also the province of molecular genetics, a field that seeks to understand heredity and the expression of genetic information in molecular terms.

Biochemistry is having a profound influence in the field of medicine. The molecular mechanisms of many diseases, such as sickle cell anemia and numerous errors of metabolism , have been elucidated. Assays of enzyme activity are today indispensable in clinical diagnosis . To cite just one example, liver disease is now routinely diagnosed and monitered by measurements of blood levels of enzymes called transaminases and of a hemoglobin breakdown product called bilirubin. Deoxyribonucleic acid (DNA) probes are coming into play in diagnosis of genetic disorders , infectious diseases, and cancers. Genetically engineered strains of bacteria containing recombinant DNA are producing valuable proteins such as insulin and growth hormone. Furthermore, biochemistry is a basis for the rational design of new drugs. Also the rapid development of powerful biochemical concepts and techniques in recent years has enabled investigators to tackle some of the most challenging and fundamental problems in medicine and physiology. For example in embryology , the mechanisms by which the fertilized embryo gives rise to cells as different as muscle, the brain and liver are being intensively investigated. Also, in anatomy , the question of how cells find each other in order to form a complex organ , such as the liver or brain, are being tackled in biochemical terms. The impact of biochemistry is being felt in so many areas of human life, through this kind of research and the discoveries are fuelling the growth of the life sciences as a whole.

The biochemistry of digestion, for example, includes the study of the pathways involving changes in molecular structure, and all enzyme interactions that take place when large food molecules (proteins, lipids, or carbohydrates) are broken down into smaller molecules capable of uptake and use by the cells of a living body.

Fundamental advances in biochemistry have also allowed important advances in genetics and molecular biology. The discovery of the composition—and subsequentely the double-helical structure—of DNA provided a critical and highly demonstrable link between biochemical form and function. The structure of the DNA molecule is remarkably well suited to its ability to make more copies of itself. The hydrogen bonds between the base pairs of the DNA double helix enable the two-stranded double helix molecule to unzip easily so that each piece can act as a pattern to build new DNA molecules.

Another area of interest to biochemists involves the flow of genetic information from DNA to RNA to protein is the same in all organisms. ATP (adenosine triphosphate ), which is the universal currency of energy in biological systems, is generated in similar ways by all forms of life. Furthermore, biochemists were able to unravel some of the central metabolic pathways and energy-conversion mechanisms. The determination of the three-dimensional structure and the mechanism of action of many protein molecules were also significant achievements in the field of biochemistry.

Identifying and sequencing genes responsible for causing diseases, and genetic cloning technology has led to remarkable progress in understanding the relationships of genes and proteins. In addition, the molecular bases of several diseases, such as sickle cell anemia , and numerous inborn errors of metabolism are now known. Biochemical assays for enzyme activities have become indispensable in clinical diagnosis.

Indeed, the field of biochemistry, which investigates the relationship between molecular structure and function of living things at a molecular level, has been profoundly transformed by recombinant DNA technology . This has led to the integration of molecular genetics and protein biochemistry. The intricate interplay of the genetic makeup (genotype) and how the molecular structure influences function and the various physical traits (phenotype) is now being unraveled at the molecular level.

See also Amino acid; Hormones; Photosynthesis.