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30PROTEINS IN BIOLOGY
Gullola Baxriddinovna To'raqulova Dildora Tolliboyevna Mamanova
Secondary school No. 41 of Ishtikhon district of Samarkand region
ABSTRACT
Proteins are chains of amino acids that perform many functions, the most important of which is enzymatic, that is, the regulation of chemical reactions in living organisms.
Keywords: biology, proteins, health, organism, functions, complex vitamins.
The vital activity of any organism is based on chemical processes. Thousands of chemical reactions take place in every cell of your body, and the combination of these reactions determines your personality. In this grandiose chemical system, protein molecules play a critical role.Let's talk about their structure at the beginning of our conversation about proteins. When designing complex molecules, you can go two ways: either use a system of modules and assemble all kinds of large molecules from a small number of structural units, or manufacture each molecule according to an individual plan. Think back to old and new building methods. Previously, all structural elements were made for only one building, and they were not found in other buildings. Nowadays, such buildings (if only they can be restored) are considered very beautiful and are appreciated above modern buildings. The modern construction method is to take ready-made parts of the same type, or modules (bricks, windows, doors), and assemble a building from them. But even in such a system, by assembling serial parts in different ways, it is possible to build a wide variety of structures. A similar approach is implemented in living systems - structural complexity is achieved due to the modular construction principle. It is this approach that is logical from the point of view of the theory of evolution, since it allows you to consistently complicate structures as new modules appear.
The main structural unit of proteins is amino acids. Molecules of this class have a similar structure, differing slightly in details. They are a chain of atoms, at one end of which there is a positively charged hydrogen ion (H +), and at the other end there is a negatively charged hydroxyl group (OH-), consisting of oxygen and hydrogen. Side groups branch off from the main chain, which are different for different amino acids. There are 21 amino acids in living organisms.
Protein is built from amino acids. This process is similar to stringing beads on a string. When two amino acids approach each other, the hydrogen ion (H +) of one of them combines with the OH -- group of the second, and the two amino acids bind to each other with the release of a water molecule. In this case, a variety of combinations
of amino acids are possible. The sequence of amino acids in the "beads" is called the primary structure of the protein. Since a bead can be any of the 21 amino acids, even for short proteins there are a huge number of possible variants of the primary structure. For example, there are over 10 trillion ways to assemble a protein that is just 10 amino acids long!
After the primary structure of the protein has been determined, under the influence of electrostatic interactions between the various side groups of amino acids, as well as between amino acids and the water surrounding them, the protein takes on a complex three-dimensional form. For us, the most important are proteins, which fold into complex spherical structures, since it is they that regulate chemical reactions in living organisms. (Other types of proteins, such as those that make up hair and other body structures, are not shaped this way.)
When complex molecules interact between specific atoms of each of the molecules, a chemical bond is formed. The ability of molecules to interact alone is not enough to form a bond. The two molecules must move closer together and take on an orientation in which the atoms capable of forming chemical bonds could dock, like spaceships in orbit. Therefore, the three-dimensional structure is of paramount importance for the chemical processes in living organisms.
It is hard to believe that two complex molecules, left to themselves, would be randomly arranged in space so that their interaction would become possible. For a chemical reaction to proceed at a noticeable rate, the participation of molecules called enzymes is necessary (see Catalysts and enzymes). The enzyme attracts both molecules to itself and gives them an orientation that allows interaction. Once the interaction has taken place, the enzyme that has done its job is released and can repeat this operation with the next pair of molecules.
Due to their complex structure, proteins perfectly cope with the role of enzymes. Each primary structure corresponds to a certain form of a protein molecule and, therefore, a certain chemical reaction that this protein catalyzes. In all living organisms, the primary structure of a protein is recorded on a DNA molecule (see Central Dogma of Molecular Biology). Thus, DNA keeps the entire organism under control, determining the spectrum of proteins formed and, thus, possible chemical reactions.
In principle, according to the primary structure of a protein, it would be possible to predict what form its molecule will have, and therefore, to predict the nature of the chemical reaction in which this protein will participate. In reality, this problem of protein folding is so complex that it cannot yet be calculated even with the best computers and software. Today this is one of the main unsolved problems in molecular biology.
Proteins (proteins, polypeptides) are high molecular weight organic substances consisting of amino acids linked into a chain by a peptide bond. In living organisms, the amino acid composition of proteins is determined by the genetic code; in the synthesis, in most cases, 20 standard amino acids are used. Their many combinations give a wide variety of properties of protein molecules. In addition, the amino acids in the protein often undergo post-translational modifications, which can occur both before the protein begins to perform its function and during its "work" in the cell. Often in living organisms, several protein molecules form complex complexes, for example, a photosynthetic complex.
The functions of proteins in the cells of living organisms are more diverse than the functions of other biopolymers - polysaccharides and DNA. Thus, enzyme proteins catalyze the course of biochemical reactions and play an important role in metabolism. Some proteins have a structural or mechanical function to form a cytoskeleton that maintains the shape of cells. Proteins also play an important role in the signaling systems of cells, in the immune response and in the cell cycle.
Proteins are an important part of the nutrition of animals and humans, since all the necessary amino acids cannot be synthesized in their bodies and some of them come from protein foods. In the process of digestion, enzymes break down consumed proteins into amino acids, which are used in the biosynthesis of body proteins or are further degraded for energy.
Determination of the amino acid sequence of the first protein, insulin, by protein sequencing won Frederick Sanger the Nobel Prize in 1958. The first three-dimensional structures of the proteins hemoglobin and myoglobin were obtained by X-ray diffraction, respectively, by Max Perutz and John Kendrew in 1958 [1] [2], for which they received the Nobel Prize in Chemistry in 1962.
Proteins were isolated into a separate class of biological molecules in the 18th century as a result of the work of the French chemist Antoine Furcroix and other scientists, in which the property of proteins was noted to coagulate (denature) under the influence of heat or acids. At that time, proteins such as albumin ("egg white"), fibrin (a protein from the blood), and gluten from wheat grains were being investigated. Dutch chemist Gerrit Mulder analyzed the composition of proteins and hypothesized that almost all proteins have a similar empirical formula. The term "protein" to denote such molecules was proposed in 1838 by Mulder's collaborator Jacob Berzelius [3].
By the end of the 19th century, most of the amino acids that make up proteins had been studied. In 1894, the German physiologist Albert Kossel put forward a theory according to which amino acids are the main structural elements of proteins [5]. At the beginning of the 20th century, German chemist Emil Fischer experimentally proved that proteins are composed of amino acid residues connected by peptide bonds. He also
carried out the first analysis of the amino acid sequence of a protein and explained the phenomenon of proteolysis
However, the central role of proteins in organisms was not recognized until 1926, when the American chemist James Sumner (later Nobel Prize winner) showed that the urease enzyme was a protein [6].
The study of proteins was hampered by the complexity of their isolation. Therefore, the first protein studies were carried out using those polypeptides that could be purified in large quantities, that is, blood proteins, chicken eggs, various toxins and digestive / metabolic enzymes that could be isolated at slaughterhouses. In the late 1950s, Armor Hot Dog Co was able to purify a kilogram of bovine pancreatic ribonuclease A, which became an experimental object for many scientists.
All amino acids contain : 1) a carboxyl group (-COOH), 2) an amino group (-NH 2 ), 3) a radical or R-group (the rest of the molecule). The structure of the radical is different for different types of amino acids. Depending on the number of amino groups and carboxyl groups that make up the amino acids, there are: neutral amino acids having one carboxyl group and one amino group; basic amino acids having more than one amino group; acidic amino acids having more than one carboxyl group.
Amino acids are amphoteric compounds , since in solution they can act both as acids and bases. In aqueous solutions, amino acids exist in different ionic forms.
REFERENCES
1. Perutz MF, Rossmann MG, Cullis AF, Muirhead H., Will G., North AC Structure of haemoglobin: a three-dimensional Fourier synthesis at 5.5-A. resolution, obtained by X-ray analysis (eng.) // Nature. - 1960.
2. Kendrew JC, Bodo G., Dintzis HM, Parrish RG, Wyckoff H., Phillips DC A three-dimensional model of the myoglobin molecule obtained by x-ray analysis (eng.) // Nature. - 1958.
3. Yu. A. Ovchinnikov. Bioorganic chemistry. - Moscow: Education, 1987. - pp . 2426.
4. Henry Leicester. Berzelius, Jons Jacob // Dictionary of Scientific Biography 2. - New York: Charles Scribner's Sons, 1980.
