Molecular biology

Animation of part of a double propeller DNA structure.

Molecular biology is the branch of biology that aims to study the processes that take place in living beings from a molecular point of view. In its modern sense, molecular biology tries to explain the phenomena of life from its macromolecular properties. Two macromolecules in particular are his object of study:

1. The nucleic acids, among which the most used is desoxyribonucleic acid (DNA), the component of genes.
2. Proteins, which are the active agents of living organisms.

Within the Human Genome Project the following definition of molecular biology can be found: The study of the structure, function and composition of biologically important molecules.

Molecular biology and other sciences

This area is related to other fields of biology and chemistry, particularly genetic engineering and biochemistry. Molecular biology is primarily concerned with understanding the interactions of different cell systems, including relationships such as those between DNA and RNA, protein synthesis, metabolism, and how all of these interactions are regulated. to achieve a correct functioning of the cell.^{[citation required]}

The difference between organic chemistry and molecular biology or biological chemistry is that in biological chemistry DNA molecules have a history and, therefore, in their structure they tell us about their history, about the past in which they have been constituted, while an organic molecule, created today, is only a witness of its present, without past and without historical evolution.

Features

Structure of a cell.

By studying the biological behavior of the molecules that make up living cells, Molecular Biology borders on other sciences that address similar issues: thus, for example, together with Genetics, it is interested in the structure and functioning of genes and in the regulation (induction and repression) of the intracellular synthesis of enzymes and other proteins. With Cytology, it deals with the structure of subcellular corpuscles (nucleus, nucleolus, mitochondria, ribosomes, lysosomes, etc.) and their functions within the cell. With Biochemistry, he studies the composition and kinetics of enzymes, being interested in the types of enzymatic catalysis, activations, competitive or allosteric inhibitions, etc. It also collaborates with Phylogenetics by studying the detailed composition of certain molecules in the different species of living beings, providing valuable data for the knowledge of evolution. However, it differs from all these listed sciences both in the specific objectives and in the methods used. to achieve them. Just as Biochemistry investigates metabolic cycles and the integration and disintegration of the molecules that make up living beings in detail, Molecular Biology intends to pay special attention to the biological behavior of macromolecules (DNA, RNA, enzymes, hormones, etc.) within of the cell and explain the biological functions of the living being by these properties at the molecular level.^{[citation needed]}

Methods

The methods that this new science employs are fundamentally the same as those of Biophysics, Biochemistry, and Biology. It uses qualitative and quantitative chemical analyses, knowledge of organic chemistry, the biology of microorganisms and viruses, etc., but the new physical and chemical microanalytics are especially important. Worth mentioning are electron microscopy, which allows resolutions up to 10 Amstrongs; X-ray diffraction, which determines the structure and spatial arrangement of the atoms of macromolecules; differential ultracentrifugation, both analytical and preparative, which allows separations that were previously impossible; gas chromatography, and, in the liquid phase, infrared spectrography, Chemistry with tracer isotopes, mass spectrometry, etc.^{[citation required]}

Content

When delving into any biological phenomenon and trying to explain the intimate nature of the processes that determine a property or a function of living beings, we inevitably enter the field of Molecular Biology. Take, for example, the study of genes. Mendel's classic laws have their immediate explanation in the morphological and functional knowledge of chromosomes. But when we want to know the composition and mode of action of a gene, we need to delve deeply into the structure of Watson and Crick's double helical DNA, the ordering of purine and pyrimidine bases, that is, genetic information.

Schematic diagram of an eukaryotic chromosome already duplicated and condensed (in metaphase mitotic). (1) Chromatide, each of the identical parts of a chromosome after the DNA duplication. (2) Centromer, the place of the chromosome in which both chromatids are touched. (3) Short arm. (4) Long arm.

When qualifying the possibility of synthesizing an enzyme by a gene, we must follow the process of transmission of this genetic information from nuclear DNA to messenger RNA; the activation of the amino acids by the carrier RNA, the ordering of these activated amino acids on the ribosome according to the pattern prefixed by the messenger RNA, the obtaining of the primary structure of the protein enzyme. All these topics are the object of study of Molecular Biology. But there is more; the protein, once synthesized, must be ordered in space according to certain rules that constitute the specific spatial conformation (secondary and tertiary structures) and sometimes associate several identical or different molecules to constitute what have been called quaternary and quinary structures, so that the biological properties of the molecule as an enzyme are linked to this complex spatial arrangement. The protein molecule thus organized may turn out to be an enzyme that, in its catalytic activity, is susceptible to activation or inhibition by certain substances, actions of transcendental importance for the life of the cell. In the same way, Molecular Biology is interested in the chemical structure of the substances that make up biological membranes and the arrangement of enzymes that carry out chained actions, p. eg, within mitochondria, nucleus and other subcellular corpuscles, to explain the mechanics of cycles and biochemical processes determined by cellular Topochemistry.^{[citation needed]}

Appropriation A=T with two hydrogen bridges. Hydrogen bridges are shown as discontinuous lines.

The reproduction processes of viruses, bacteria, and higher organisms contain a multitude of unknowns that molecular biology tries to solve. Mutations produced by physical agents (X-rays, gamma rays, heat, etc.) or chemicals (mutagenic substances) have an explanation that is all the more satisfactory the better the molecular basis of the processes of alteration in the structure and ordering of the bases is known. nitrogenous cells of DNA.^{[citation needed]}

The relationship between different species of living beings can be established through the individual comparative study of the macromolecular substances (proteins) produced by them. Thus, from the sequence of amino acids in hemoglobin, myoglobin, cytochromes, pituitary hormones or insulin, the degree of phylogenetic proximity is induced, by demonstrating the evolution of the protein by progressive mutations. A multitude of genetic phenomena such as natural selection, adaptation to the environment, differentiation of species, etc., have their ultimate explanation at the molecular level. Finally, the molecular biology of microorganisms is providing interesting data for the search for new antibiotics and antimetabolites, which make it possible to attack pathogens efficiently and selectively.^{[citation required]}

With all this we do not want to affirm that Molecular Biology is a complete or perfectly elaborated science. Quite the opposite; New discoveries, when solving a mystery, raise many more questions that are the subject of future research. Today this young science is in explosive expansion. On the other hand, the last and definitive explanation of the behavior of the molecules of living beings requires, to be known in depth, confronting other branches of science such as submolecular biophysics (orbitals, bonding forces, hybridization, etc.) and even subatomic physics, for which a wealth of knowledge is required that can never be the heritage of isolated researchers, but of scientifically heterogeneous work teams, but harmoniously combined.^{[citation required ]}

Notable Molecular Biologists

• Francis Crick
• James Dewey Watson
• Rosalind Franklin
• Max Perutz
• François Jacob
• Christiane Nüsslein-Volhard
• Severo Ochoa
• Alberto Kornblihtt
• Linus Pauling