The importance, role and function of proteins in the cell. What function does the squirrel perform in the cell?

Proteins are the most important organic substances, the number of which predominates over all other macromolecules that are present in the living cell. They make up more than half the weight of the dry matter of both plant and animal organisms. The functions of proteins in the cell are diverse, some of them are still unknown to science. Nevertheless, the main directions of their "work" are well studied. Some are needed in order to stimulate the processes taking place in cells and tissues. Others carry important mineral compounds through the cell membrane and through the blood vessels from one organ to another. Some protect the body from foreign, often pathogenic agents. One thing is clear - no proteins are leaked by any process in our body.

Basic functions of proteins

Functions of proteins in the body are diverse. Each group has a certain chemical structure, performs one specialized "work". In some cases, several types of proteins are interrelated. They are responsible for the different stages of a single process. Or they affect several people at once. For example, the regulatory function of proteins is carried out by enzymes and hormones. This phenomenon can be imagined, remembering the hormone adrenaline. It is produced by the adrenal medulla. Entering the blood vessels, it increases the amount of oxygen in the blood. Blood pressure also rises, the sugar content increases. This stimulates metabolic processes. Also adrenaline is the mediator of the nervous system in fish, amphibians and reptiles.

Enzymatic function

Numerous biochemical reactions taking place in the cells of living organisms are carried out at high temperatures and with a neutral pH. In such conditions, the rate of their passage is too small, so specialized catalysts called enzymes are needed. All their diversity is combined into 6 classes, which differ in the specificity of the action. Enzymes are synthesized on ribosomes in cells. Their study deals with the science of enzymology.

Undoubtedly, without enzymes, the regulatory function of proteins is impossible. They have a high selectivity of action. Their activity can be regulated by inhibitors and activators. In addition, enzymes usually exhibit specificity with respect to substrates. Also, the enzymatic activity depends on the conditions in the body and in the cells in particular. Their flow is affected by pressure, acid pH, temperature, ionic strength of the solution, that is, the concentration of salts in the cytoplasm.

Transport function of proteins

The cell must constantly receive the necessary mineral and organic substances. They are needed as building materials and energy sources in cells. But the mechanism of their receipt is rather complicated. Cellular membranes consist not only of proteins. Biological membranes are built on the principle of a double layer of lipids. Various proteins are built between them. It is very important that the hydrophilic areas are on the surface of the membrane, and the hydrophobic regions are in its thickness. Thus, such a structure makes the envelope impenetrable. Through it, they can not independently, without "help", go through such important components as sugars, ions of methols and amino acids. Through the cytoplasmic membrane into the cytoplasm, they are transported by specialized proteins that are embedded in the layers of lipids.

Transport of substances from one organ to another

But the transport function of proteins is realized not only between the intercellular substance and the cell. Some substances important for physiological processes have to be delivered from one organ to another. For example, the transport protein of blood is serum albumin. It is endowed with a unique ability to form compounds with fatty acids, which appear when digesting fats, with medicines, as well as with steroid hormones. Important carrier proteins are hemoglobin (delivering oxygen molecules), transferrin (which combines with iron ions) and ceruplazmin (forming complexes with copper).

Signal function of proteins

Protein-receptors are of great importance in the course of physiological processes in multicellular complex organisms. They are mounted in the plasma membrane. They serve for the perception and decoding of various kinds of signals that flow continuously into the cells not only from neighboring tissues, but also from the external environment. At the present time, perhaps the most studied protein-receptor is acetylcholine. It is located in a series of interneuronal contacts on the cell membrane.

But the signal function of proteins is not only inside cells. Many hormones bind to specific receptors on their surface. Such a formed connection is a signal that activates physiological processes in cells. An example of such proteins is insulin acting in the adenylate cyclase system.

Protective function

The functions of proteins in the cell are different. Some of them are involved in immune responses. This protects the body from infections. The immune system is able to respond to the detected foreign agents by the synthesis of a huge number of lymphocytes. These substances are capable of selectively damaging these agents, they can be foreign to the body, for example bacteria, supramolecular particles, or it can be cancer cells.

One of the groups - beta-lymphocytes - produces proteins that fall into the bloodstream. They have a very interesting function. These proteins should recognize foreign cells and macromolecules. Then they connect with them, forming a complex, which is subject to destruction. These proteins are called immunoglobulins. The foreign components themselves are antigens. And immunoglobulins, which correspond to them - antibodies.

Structural function

In the body, in addition to highly specialized, there are also structural proteins. They are necessary to provide mechanical strength. These functions of proteins in the cell are important to maintain the shape and preserve the youth of the body. The most famous is collagen. It is the main protein of the extracellular matrix of connective tissues. In higher mammals, it is up to 1/4 of the total mass of proteins. Collagen is synthesized in fibroblasts, which are the main cells of connective tissues.

Such functions of proteins in the cell are of great importance. In addition to collagen, another structural protein, elastin, is known. It is also a constituent of the extracellular matrix. Elastin is able to give the tissue the ability to stretch within certain limits and easily return to its original shape. Another example of a structural protein is fibroin, which is found in silkworm caterpillars. This is the main component of silk threads.

Motor proteins

The role of proteins in the cell can not be overestimated. They take part in the work of muscles. Muscle contraction is an important physiological process. As a result, ATP is converted into chemical energy stored as macromolecules. The immediate participants in the process are two proteins - actin and myosin.

These motor proteins are filamentary molecules that function in the contractile system of skeletal muscles. They are also found in non-muscle tissues in eukaryotic cells. Another example of motor proteins is tubulin. From it microtubules are constructed, which are an important element of flagella and cilia. Also microtubules containing tubulin are detected in the cells of the nervous tissue of animals.

Antibiotics

The protective role of proteins in the cell is enormous. Part of it is placed on a group, which is called antibiotics. These are substances of natural origin, which are synthesized, as a rule, in bacteria, microscopic fungi and other microorganisms. They are aimed at suppressing the physiological processes of other competing organisms. Antibiotics of protein origin were discovered in the 1940s. They revolutionized medicine, giving it a powerful impetus to development.

In its chemical nature, antibiotics are a very diverse group. They differ in the mechanism of action. Some interfere with the synthesis of protein inside cells, the second block the production of important enzymes, others suppress growth, the fourth - the reproduction. For example, well-known streptomycin interact with ribosomes of bacterial cells. Thus, protein synthesis is dramatically slowed down in them. At the same time, these antibiotics do not interact with the eukaryotic ribosomes of the human body. This means that for higher mammals these substances are not toxic.

This is not all the functions of proteins in the cell. The table of antibiotic substances makes it possible to determine other highly specialized actions that these specific natural compounds can exert on bacteria and not only. At present, studies are under way of antibiotic proteins, which, when interacting with DNA, violate the processes associated with the embodiment of hereditary information. But while such substances are used only for chemotherapy of oncological diseases. An example of such an antibiotic substance is dactinomycin synthesized by actinomycetes.

Toxins

The proteins in the cell perform a very specific and even non-ordinary function. A number of living organisms produce poisonous substances - toxins. By their nature, these are proteins and complex low-molecular organic compounds. As an example, you can bring a poisonous fungus fungus pale toadstool.

Spare and food proteins

Some proteins fulfill the function of providing nutrition to embryos of animals and plants. There are many such examples. It is precisely in this that the value of the protein in the seed cell of cereals lies. They will nourish the emerging rudiment of the plant at the first stages of its development. In animals, dietary proteins are egg albumin and milky casein.

Unexplored properties of proteins

The above examples are only the part that has already been sufficiently studied. But in nature there are many mysteries. The proteins in the cell of many species are unique, and now it is difficult to even classify them. For example, monellin is a protein found and isolated from an African plant. It tastes sweet, but it does not cause obesity and is not toxic. In the future, this can be an excellent substitute for sugar. Another example - a protein found in some Arctic fishes, it prevents the freezing of blood, acting as an antifreeze in the literal sense of this comparison. A number of insects in wing joints revealed a protein of rubber, which has a unique, almost ideal elasticity. And this is by no means all examples of substances that are yet to be studied and classified.