The famous philosopher Karl Marx at one time proposed the following definition of the concept of "life" - this is a form of existence of protein bodies. And with this statement it is impossible to argue. The basis of any animal organism is precisely this substance. What features determine their most important functions? How do proteins function? The classification, structure and structures of these substances will be considered in our article.
The concept of organic matter
The group of organic substances that make up living 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 glycerol polyhydric alcohol and fatty acids. Such repeating parts are called monomers. Proteins are no exception. The classification of proteins and other organic substances in most cases is based on their structure.
Protein is the basis of life
It is traditionally believed that only animal organisms have a protein basis. Indeed, in order to get rich in this substance, we use pork and beef meat, poultry, eggs and fish. But a large amount of this substance is found in plant foods. Legumes (beans, peas, peanuts, soybeans) are a storehouse of plant proteins.
Protein structure
Proteins are simple, but at the same time unique in their structure. They are formed by monomers called amino acids. This is the only organic substance of living organisms, which include the chemical element nitrogen.
One protein consists of twenty amino acids. In turn, each monomer consists of a carbon atom to which the element hydrogen, an amino group, a carboxyl group and a radical are attached. This is a group of atoms in which amino acids differ from each other. That is why proteins are so diverse in structure and function.
Protein Structures
Depending on the complexity of the structure, four protein structures are distinguished:
1. The primary is a chain of amino acids connected by peptide bonds. They occur at the junction of the amino and carboxy groups.
2. Secondary - the amino acid chain is twisted into a spiral. The bonds that form in this structure are called hydrogen.
3. Tertiary is a globule. It is a ball of twisted spirals of a secondary structure.
4. Quaternary - globules of molecules representing a combination of several similar structures.
The last structure can be untwisted to 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.
Proteins: protein classification
Depending on the chemical composition, simple and complex proteins are distinguished . The former consist only of amino acids, the latter additionally includes a prosthetic group. It is a component of non-protein nature.
The classification of simple proteins (proteids) is based on their chemical nature. For example, histones and protamines have basic properties, since most of them are composed of arginine. They are an integral element of complex proteins and are part of cell nuclei. Prolamins are proteins of plant origin and are found in large quantities in cereal seeds. Albumin and globulins are components of human blood.
The classification of complex proteins is related to the nature of the prostatic group. So, the composition of glycoproteins, in addition to amino acids, includes carbohydrate residues.
Casein of milk, albumin of bird eggs, ichthulin of fish roe are also complex proteins. They are called phosphoproteins containing the structural part of a mineral acid.
Residues of DNA and RNA, together with amino acids, are part of nucleoproteins, which are an integral part of cellular structures.
In blood plasma, lung tissue, mitochondria, cell membranes are lipoproteins. Their prostatic group consists of derivatives of fats.
That's 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 independently form in the human body. They are called interchangeable. Amino acids of another type can enter it only 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.
Classification of proteins by function
By functional principle, several groups of these most important organic substances are distinguished. 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 , break down complex carbohydrates to simple ones already in the oral cavity. In the stomach, the lipase enzyme emulsifies fats to monomers. There is a group of proteins that have the opposite effect, slowing down the rate of reactions. They are called inhibitors.
Hormones are also protein substances. In humans and animals, they are secreted by special organs called glands. So, the pituitary gland located at the base of the brain releases growth hormone. It enters the bloodstream, where it accumulates, gradually affecting quantitative changes in the body.
Protective blood proteins are called antibodies. Their function is to neutralize foreign 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.
The transport protein globin is a part of red blood cells that carry out gas exchange. Actin and myosin are contractile proteins of muscle tissue.
Here are so diverse in structure and capabilities are proteins. The classification of proteins is based on the features of their chemical composition and functional features.