The normal activity of the body is possible when continuous supply of food. Included in the composition of food fats, proteins, carbohydrates, minerals, water and vitamins needed for life processes of the body.
Nutrients are a source of energy that covers the cost of the organism, and building materials that are used during the body's growth and reproduction of new cells replacing dying. But the nutrients in the form in which they are eaten, can not be soaked and can be utilized by the body. Only water, mineral salts and vitamins are absorbed and assimilated in the form in which they are received.
Nutrients are called proteins, fats and carbohydrates. These substances are essential constituents of food. In the digestive tract of proteins, fats and carbohydrates are both physical impacts (crushed and triturated), and chemical changes that occur under the influence of special substances - enzymes - contained in the juices of the digestive glands. Under the influence of digestive juices nutrients broken down into simpler ones, which are absorbed and assimilated by the body. Proteins. Structure, Properties and Functions
"All plants and animals there is some substance which, without a doubt the most important of all known substances of nature, and without which life would have been impossible on our planet. This substance is a protein he named me "- so wrote back in 1838, a Dutch biochemist Gerard Mulder, who first discovered the existence in the nature of protein bodies and formulated his theory of protein. The word "protein" (protein) derived from the Greek word "proteyos", which means occupying the first place. " And indeed, all life on earth contains proteins. They constitute about 50% of the dry weight of all organisms. Do virus protein content ranged from 45 to 95%.
Proteins are one of the four main organic compounds of living matter (proteins, nucleic acids, carbohydrates, fats), but its significance and biological functions, they occupy a special place. About 30% of all proteins of the human body is in muscle, about 20% - in the bones and tendons, and about 10% - in the skin. But the most important proteins of all organisms, are enzymes which, although present in the body and every cell in the body in small amounts, however, manage a number of significant importance for the life of chemical reactions. All processes in the body - digestion, oxidation reactions, the activity of the endocrine glands, muscle activity and work of the brain - are regulated by enzymes. A variety of enzymes in the body of organisms is enormous. Even in a small bacteria numbering many hundreds.
Proteins, or as they are otherwise called, the proteins have a very complicated structure and are the most complex of nutrients. Proteins - mandatory component of all living cells. The structure of proteins include: carbon, hydrogen, oxygen, nitrogen, sulfur, and sometimes phosphorus. The most characteristic protein presence in the molecule of nitrogen. Other foods do not contain nitrogen. Therefore, a protein called nitrogenous substance.
Basic nitrogen-containing substances, which make up proteins - this amino acid. Small number of amino acids - their only known 28. All the great diversity contained in the nature of proteins represents a different combination of common amino acids. From a combination of both dependent properties and qualities of protein.
Proteins play a vital role in nature. Life is unthinkable without the various on structure and function of proteins. Protein - a complex structure of biopolymers, macromolecules (proteins) are composed of amino acid residues connected by an amide (peptide) bond. In addition to long polymer chains are constructed from amino acid residues (polypeptide chains), a protein macromolecule may comprise the remnants of the molecules or other organic compounds. On the one ring of each peptide chain is free or acylated, amino group, on the other - a free or amidated, the carboxyl group.
End of the chain with the amino group is called the M-terminus, the end of the chain with the carboxyl group - the C-terminus of the peptide chain. Between the CO group of one peptide group and NH group of another peptide groups can easily form hydrogen bonds.
Group belonging to the radical R of amino acids can interact with each other, with the foreign material and with neighboring proteins and other molecules, forming a complex and diverse structure.
In the macromolecule of the protein contains one or more peptide chains linked together by transverse chemical bonds, usually through the sulfur (disulfide bridges formed by cysteine residues). Chemical structure of peptide chains is called the primary structure of protein, or a sequent.
To construct the spatial structure of the protein peptide chains must accept a certain inherent in the given protein configuration, which is fixed by hydrogen bonds that occur between the peptide groups of individual sections of the molecular chain. As the formation of hydrogen bonds the peptide chains are twisted in a spiral, trying to form a maximum number of hydrogen bonds and, accordingly, to the energetically most favorable configuration.
For the first time such a structure based on X-ray analysis was found in the study of the principal protein of hair and wool - keratin - Pauling, an American physicist and chemist. It was called a-structure or a-helix. One helix turn accounting for 3.6 - 3.7 amino acid residues. The distance between the turns - about 0.54 billion shares meters. Helix structure is stabilized by intramolecular hydrogen bonds.
When you stretch the helix protein macromolecule is converted to another structure similar to a linear one.
But the formation of the correct helix often hinder the forces of repulsion or attraction arising between groups of amino acids, or steric hindrance, for example, through the formation of pyrrolidine rings of proline and hydroxyproline, which force the peptide chain sharply bends and prevent the formation of spirals in some of its stations. Further, some parts of the protein macromolecules are oriented in space, taking in some cases quite elongated, and sometimes strongly curved, convoluted spatial structure.
Spatial structure is fixed, the interaction of the radicals R and amino acids to form disulfide bridges, hydrogen bonds, ion pairs or other chemical or physical bonds. It is the spatial structure of a protein determines the chemical and biological properties of proteins.
Depending on the spatial structure of all proteins are divided into two classes: the fibrillar (they used nature as a structural material) and globular (enzymes, antibodies, some hormones, etc.).
Polypeptide chains of fibrous proteins have a spiral shape, which is located along the chain is fixed by intramolecular hydrogen bonds. In the fibers of fibrous proteins spun peptide chains are arranged parallel to the fiber axis, as if they are oriented relative to each other, are located side by side, forming a filamentary structure, and have a high degree of asymmetry. Fibrillar proteins are poorly soluble or completely insoluble in water. When dissolved in water, they form a high viscosity solutions. By the fibrous proteins are proteins that make up the tissues and the integumentary structures. This myosin - the protein of muscle tissue, collagen, which is the basis of sedimentary fabric and skin, keratin, which is part of the hair, horn covers, wool and feathers. To the same class of proteins include natural silk protein - fibroin - a viscous liquid and solidifying in the air in a solid insoluble thread. This protein has an elongated polypeptide chain, connected to each other by intermolecular hydrogen bonds, which determines, apparently, high mechanical strength of natural silk.
Peptide chains of globular proteins is strongly bent, folded, and often take the form of hard balls - globules. Globular protein molecules have a low degree of asymmetry, they are highly soluble in water, and viscosity of their solutions small. This, above all, blood proteins - hemoglobin, albumin, globulin, etc.
It should be noted conventional divisions of proteins in the fibrillar and globular, as there are a large number of proteins with an intermediate structure.
Properties of the protein can vary greatly in replacement of one amino acid on the other. This is due to changes in the configuration of peptide chains and the conditions for the formation of the spatial structure of the protein, which ultimately determines its function in the body.
The number of amino acid residues within the individual molecules of proteins, is quite different: insulin - 51 in myoglobin - 140. Therefore, the relative molecular mass of proteins varies in a very wide range - from 10 thousand to many millions. On the basis of determining the relative molecular mass and elemental analysis established the empirical formula of a protein molecule - hemoglobin (C738H1166O208S2 Fe) 4. Lower molecular weight can be a simple enzymes and some hormones of protein nature. For example, the molecular weight of the hormone insulin, about 6500, and the protein of the influenza virus - 320000000. Substance of protein nature (consisting of amino acid residues, connected by a peptide bond), having relatively smaller molecular weight and lower degree of spatial organization of macromolecules, called polypeptides. Draw a sharp boundary between proteins and polypeptides difficult. In most cases the proteins are different from other natural polymers (rubber, starch, cellulose), so that net individual protein contains only molecules of similar structure and weight. The exception is, for example, gelatin, which consists of macromolecules with molecular weight 12000 - 70000.
Structure of proteins explained their very different properties. They have different solubility: some dissolve in water, others - in dilute solutions of neutral salts, and some do not possess the solubility (eg, proteins integumentary tissues). By dissolving protein in water formed a kind of molecular dispersion system (a solution of high molecular substances). Some proteins can be isolated as crystals (egg white, blood hemoglobin).
Proteins play a crucial role in the life of all organisms. During digestion protein molecules are digested to amino acids, which, being highly soluble in water, penetrated into the bloodstream and enter into all tissues and cells. Here, most of amino acids consumed in the synthesis of proteins of various organs and tissues, and some - the synthesis of hormones, enzymes and other biologically important substances, and the others serve as an energy material. Ie proteins have catalytic (enzymes), regulators (hormones), transport (hemoglobin, ceruloplasmin, etc.) and protective (antibodies, thrombin, etc.) to function.
Proteins - essential components of human food and animal feed. Collection of continuously occurring chemical reactions of proteins is a leader in the metabolism of organisms. Update rate of proteins in living organisms depend on the protein content in food, as well as its biological value, which is determined by the presence and ratio of essential amino acids
Proteins Plant poorer animal proteins on the content of essential amino acids, especially lysine, methionine, tryptophan. Soy protein and amino acid composition of potato in the closest animal protein. Lack of essential amino acids in the diet comes to serious violations of nitrogen metabolism. Therefore, selection of cereals aimed, in particular, and to improve the quality of the protein composition of grain.
