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Lecture notes, cheat sheets
Concepts of modern natural science. Biophysics (lecture notes)
Directory / Lecture notes, cheat sheets Table of contents (expand) LECTURE No. 8. Biophysics 1. General concepts and history Biophysics is a science that studies the physical and physico-chemical phenomena that occur in living organisms. Also, this science studies the structure and properties of biopolymers, as well as the influence of various physical factors on living organisms and living systems. For the longest period in human history, the sciences were thought to be "immiscible". Many centuries passed, and mankind realized that for further development it is necessary to study "hybrid sciences". The world's first attempts to apply physical methods and ideas to the study of a living organism were made as early as the XNUMXth century. Further development of biophysics is associated with: 1) studying the works of Luigi Galvani. In his works, he put forward the existence of "animal electricity" (more about it will be discussed below); 2) the study of the works of G. Helmholtz, as well as the study and development of acoustics and optics; 3) the study of the mechanics and energetics of living organisms; 4) the study of the works of P. P. Lazarev and the works of Yu. Bernshtein, as well as the study of the ionic and membrane theory of excitation. Biophysics studies integral systems without decomposing them into their component parts. If, however, component parts are singled out, then in the process of such "allocation" of the particular from the whole, the properties of the integral system that are important for the further normal existence of the system will be lost. This will primarily have a negative impact on biophysical science itself. Polymers function normally only in the conditions of an undisturbed, integral system. Therefore, biophysicists must invent new techniques and research methods. The main feature of such methods is that they study polymers precisely in the conditions in which they live. If the properties and processes of the cell, important for the further normal existence, were violated, then, accordingly, its physical and chemical parameters also change. Under certain influences, a cell may lose a number of its abilities (for example, the ability to polarize), although the appearance of the cells may remain unchanged. But a cell can not only lose its abilities, but also acquire so-called artifacts. Artifact for biophysics are newly formed structures and compounds. The main feature of artifacts is that they are not present in undamaged cells, i.e., in whole cells. With the advent of microscopes, and then with the use of electron microscopes, the boundaries of the study of biology, chemistry, biophysics and many other sciences have significantly expanded. Scientists, using the methods of electron microscopy, are trying to reveal the details of the fine structure of a molecular substance. At the same time, they can stumble upon artifacts. What can this lead to? And here's what: 1) if the artifact is indistinguishable by external features, then this can lead to erroneous results. In addition to "external similarity", here also play a significant role such factors as the presence of sufficient knowledge of the scientist and the manifestation of his maximum attention in the process of studying the cell; 2) an artifact can be discovered if the scientist has sufficient knowledge and information, and also showed maximum attention. Biophysical science faces a number of complex theoretical and practical tasks. These tasks are within the competence of biophysics, and other sciences can assist it: 1) the issue of energy exchange in a biological substrate; 2) study of the role of submicroscopic and physico-chemical properties and structures in the vital activity of cells and tissues; 3) the emergence of excitation and the origin of bioelectric potentials; 4) issues of autoregulation of physical and chemical processes in living organisms. The significance of the fourth task, i.e., the task concerning the issues of autoregulation of physicochemical processes in living organisms, lies in the fact that supramolecular structures that are absent in living organisms were identified in histological preparations. It has been well established that living cells have the following properties: 1) the presence of an electrical potential between the cell itself and its environment; 2) a living cell maintains an ion gradient in potassium and sodium between the cell and its environment; 3) the ability to polarize electric current. These properties are unique to living cells. One of the most prominent roles in the history of the emergence and development of biophysics was played by the outstanding scientist Luigi Galvani. 2. Luigi Galvani, his theory. Dispute with Volt Luigi Galvani (1737-1798) - an outstanding scientist, he studied anatomy and physiology. Galvani became one of the founders of the doctrine of electricity. Luigi Galvani is also known for being the first to draw attention to the fact that electrical phenomena occur during muscle contraction (this effect, or rather, the phenomenon, was called "animal electricity"). Luigi Galvani was born on September 9, 1737 in Italy, in the city of Bologna. He did not plan to study science, but sought solitude and wanted to converse in his prayers with the Creator, God. Therefore, Galvani first prepared to take the veil as a monk, but he did not succeed in leaving to live in a monastery. Most likely, Galvani realized that the ascetic way of life was not for him, and world history acquired another outstanding scientist. Galvani entered the local university, after graduating from which in 1759 he began to prepare his scientific dissertation. Luigi Galvani spends whole years on his scientific work. In 1762, Galvani successfully defended his dissertation, which was called "On Bones". Galvani's success was so great that he immediately took the post of head of the anatomy department of the university, from which he had recently graduated. Thus, the work of the young scientist was appreciated. In parallel with his scientific work, Luigi Galvani was also engaged in practice: surgery and obstetrics. After 12 years, in 1774, Galvani, conducting an experiment on a frog, discovers "animal electricity". Luigi Galvani became interested in this phenomenon as a physiologist. He was interested in the ability of a dead drug to manifest itself as a living material. He changed the position of the metal wire in the body of the frog, changed the current sources and many other parameters. Conducting such an experiment, Luigi Galvani wanted to use natural electricity as a current source, but the weather was clear and there was not a cloud in the sky. The scientist, purely by chance, pressed the electrodes, which were stuck into the spinal cord of the frog, to the iron grate on which the frog was lying. Luigi Galvani was very surprised when he saw that the same contractions appeared as during the experiments that were carried out during a thunderstorm. Luigi Galvani was even more surprised when he found out that muscles contract even when there is no external current source. It turned out that the muscles begin to contract even when two plates of different metals are simply placed on them, connected by a conductor. Another well-known scientist, physicist Alessandro Volta, became interested in these experiments of the physiologist Luigi Galvani. Volta suggested that electricity resides in those two plates of different metals that Galvani used. And electricity arises when these plates are connected by a conductor. Thus, the physicist Alessandro Volta became an opponent in a scientific dispute with the physiologist Luigi Galvani. Thus began the greatest controversy between the two scientists. Alessandro Volta insisted that the source of electricity was metals, while another insisted that the source of current was animals. Both scientists conducted experiments to confirm their theory. Luigi Galvani, it seemed to him, found irrefutable evidence for his point of view, which consists of two elements: 1) proved that electricity arises without the participation of metals; 2) having removed the skin from the nerve of the frog's leg, Luigi Galvani brought it to the muscles. The muscle began to contract. Alessandro Volta, however, did not calm down and did not back down. He also gave very, very convincing evidence in favor of his point of view. Although both Galvani and Volta believed that only one of them was right in the dispute, after a long period of time it became clear that both points of view have a right to exist. Alessandro Volta was a compatriot of Luigi Galvani, as both of them were born in Italy, but in different cities. His most important contribution to the development of science was his invention of a fundamentally new direct current source. In 1800, Alessandro Volta created the so-called voltaic pillar. It was the first chemical source of electricity. The name of Alessandro Volta was immortalized by the fact that the unit of potential difference of the electric field (volt) was named after him. Volta received his well-deserved recognition in the 1800th century. In XNUMX, Napoleon Bonaparte opened a university in Pavia and Volta was appointed professor of experimental physics. Volta was also introduced to the commission of the Institute of France; a few years later he receives a gold medal, as well as the award of the first consul; he is invited to work in St. Petersburg. The Pope assigns him a lifetime pension, and in France he receives the Order of the Legion of Honor. Later, Volta moved to live and work in Austria, at the University of Pavia. By this time, the scientist had already been awarded the noble title of count. The Austrian authorities took care of Volt so much that they allowed him to work without attending the service, and also confirmed his right to a lifetime pension. In Pavia, Volta was dean of the Faculty of Philosophy. Alessandro Volta died on March 5, 1827 in his homeland, in the Italian city of Como. Author: Filin S.P. << Back: Biochemistry (The concept of biochemistry, the history of its appearance. Belozersky Andrey Nikolaevich and his scientific works) >> Forward: Time (Homogeneity of time. Continuity of time. Unidirectionality of time)
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