The famous philosopher Karl Marx in his timeproposed the following definition of the concept of "life" - this is the form of the existence of protein bodies. And with this statement it is impossible to argue. At the heart of any animal organism is this substance. What features determine their most important functions? How do proteins function? Classification, structure and structures of these substances will be considered in our article.
To the group of organic substances that make up theliving organisms, include proteins, lipids, carbohydrates and nucleic acids. All of them are biopolymers - complex structures, consisting of a large number of repeating parts. For example, lipids are composed of polyhydric alcohol glycerol and fatty acids. Such repeating units are called monomers. Proteins are not an exception. The classification of proteins and other organic substances in most cases is based on their structure.
Traditionally it is considered that the protein basishave only animal organisms. And really, to enrich this substance, we use pork and beef meat, poultry, eggs and fish. But a large amount of this substance is contained in plant products. Fruits of legumes (beans, peas, peanuts, soybeans) are a storehouse of vegetable proteins.
Proteins are simple, but at the same timeunique in their structure. They are formed by monomers, which are called amino acids. This is the only organic substance of living organisms, which includes a chemical element of nitrogen.
One protein consists of twenty amino acids.In turn, each monomer consists of a carbon atom to which an element hydrogen, an amino group, a carboxyl group and a radical is attached. This is a group of atoms, according to which amino acids differ from each other. That's why proteins are so diverse in structure and functions.
Depending on the complexity of the structure, four protein structures are distinguished:
1. Primary is a chain of amino acids linked by peptide bonds. They arise at the junction of the amino and carboxyl groups.
2. Secondary - the amino acid chain is twisted into a spiral. The bonds that form in this structure are called hydrogen bonds.
3. Tertiary is a globule. It is a ball of twisted spirals of the secondary structure.
4. Quaternary - globules of molecules, representing a combination of several similar structures.
The latter structure can be untwisted to the primary and vice versa. These processes are reversible and are called de- and renaturation. The process of destruction of the primary structure - destruction - is irreversible.
Depending on the chemical compositionsimple and complex proteins. The first consist only of amino acids, the second part additionally includes a prosthetic group. It is a component of non-protein nature.
Classification of simple proteins (proteins) is based onon their chemical nature. For example, histones and protamines have basic properties, as most consist of arginine. They are an integral element of complex proteins and are part of the cell nuclei. Prolamins are proteins of plant origin and in large quantities are contained in seeds of cereals. Albumins and globulins are the components of human blood.
Classification of complex proteins is associated with the nature of the prostatic group. Thus, glycoproteins, in addition to amino acids, contain carbohydrate residues.
Milk casein, albumin of bird eggs, ichthyolin of fish eggs are also complex proteins. They are called phosphoproteins, which contain the structural part of the mineral acid.
The DNA and RNA residues, together with amino acids, are part of the nucleoproteins that are part of the cellular structures.
In blood plasma, lung tissue, mitochondria, cell membranes are lipoproteins. Their prostatic group consists of fat derivatives.
Here are so diverse in the structure of proteins.The classification of proteins can also be based on the origin of their amino acids. Some of them are able to form independently in the human body. They are called interchangeable. Amino acids of a different type can only enter into it from the outside. These are essential amino acids. Some of them are of animal origin only. Therefore, scientists argue that meat food is necessary for the normal development of the human body.
According to the functional principle, there are severalgroups of these most important organic substances. Enzymatic proteins are biological catalysts. They accelerate the course of chemical reactions, while not being part of its products. For example, amylase and maltase, which are part of human saliva, split complex carbohydrates to simple ones already in the oral cavity. In the stomach, the lipase enzyme emulsifies fats to monomers. There is also a group of proteins having the opposite effect, slowing down the rate of reactions. They are called inhibitors.
Hormones are also substances of proteinnature. In the human body and animals, they are isolated by special organs called glands. So, the pituitary gland located at the base of the brain, secretes growth hormone. It enters the blood, where it accumulates, gradually affecting the quantitative changes in the body.
Protective proteins of the blood are called antibodies.Their function is to neutralize alien and viral particles that enter the body. Antibodies are able to recognize them and destroy them by phagocytosis - intracellular digestion. The functioning of protective proteins determines the level of human immunity, which is the ability to withstand diseases of a viral and bacterial nature.
Transport protein globin is a part of red blood cells, which carry out gas exchange. Actin and myosin are contractile proteins of muscle tissue.
Here are such a diverse in structure and capabilities are proteins. The classification of proteins is based on the features of their chemical composition and functional characteristics.
