What layers consists of a cell membrane. Cell membranes, their structure. Membrane functions cells

Cell - self-regulatory structural and functional unit of tissues and organs. The cellular theory of the structure of organs and tissues was developed by Shleden and Schwann in 1839. In the future, with the help of electron microscopy and ultracentrifugation, it was possible to find out the structure of all major organlell of animals and vegetable cells (Fig. 1).

Fig. 1. The scheme of the structure of the cell of animal organisms

The main parts of the cell are cytoplasm and kernel. Each cell is surrounded by a very thin membrane that limits its contents.

Cell membrane is called Plasma membrane and characterized by selective permeability. This property allows the necessary nutrients and chemical elements to penetrate the cells, and excessive products leave it. The plasma membrane consists of two layers of lipid molecules with the inclusion of specific proteins into it. The main lipids of the membrane are phospholipids. They contain phosphorus, polar head and two non-polar tails from long-chain fatty acids. Cholesterol and cholesterol esters include membrane lipids. In accordance with the liquid-mosaic model of the structure, the membranes contain the inclusion of protein and lipid molecules that can be mixed relative to the bislo. For each type of membranes of any animal cell characterized by its relatively permanent lipid composition.

The membrane proteins according to the structure are divided into two types: integral and peripheral. Peripheral proteins can be removed from the membrane without its destruction. There are four types of membrane proteins: transport proteins, enzymes, receptors and structural proteins. Some membrane proteins have enzymatic activity, others associate certain substances and contribute to their transfer inside the cell. Proteins provide several ways to move substances through membranes: form large pores consisting of several protein subunits that allow water molecules and ions between cells; Ionic channels are formed, specialized to move the ions of some species through the membrane under certain conditions. Structural proteins are associated with the inner lipid layer and provide cell cytoskel. The cytoskeleton gives the mechanical strength of the cell shell. In various membranes, proteins accounted for from 20 to 80% of the mass. Membrane proteins can freely move in the lateral plane.

The membrane contains and carbohydrates that can covalently bind to lipids or proteins. It is known three types of membrane carbohydrates: glycolipids (gangliosides), glycoproteins and proteoglycans. Most membrane lipids are in liquid state and have a certain fluidity, i.e. The ability to move from one site to another. On the outside of the membrane there are receptor sites connecting various hormones. Other specific areas of the membrane could be recognized and associated some alien proteins for these cells and a variety of biologically active compounds.

The inner space of the cell is filled with cytoplasm, in which most cellular metabolic reactions catalyzed by enzymes proceeds. The cytoplasm consists of two layers: an internal, called endoplasm, and peripheral - ectoplasm, which has a greater viscosity and deprived of the granules. In the cytoplasm there are all cell components or organelles. The most important from organelles cells are - endoplasmic reticulum, ribosomes, mitochondria, Machinery, Lizosomes, microfilaments and microtubule, peroxisoma.

Endoplasmic reticulum It is a system of interrelated channels and cavities that permeate the entire cytoplasm. It provides vehicle weighs from the environment and inside the cells. The endoplasmic reticulum also serves as a depot for intracellular ions Ca 2+ and serves as the main site of lipid synthesis in the cell.

Ribosomes - Microscopic spherical particles with a diameter of 10-25 nm. Ribosomes are freely located in the cytoplasm or attached to the outer surface of the membrane of the endoplasmic network and the nuclear membrane. They interact with informational and transport RNA, and protein synthesis is carried out. They synthesize proteins that fall inside the tanks or in the Golgi apparatus, and then allocated outward. Ribosomes, freely located in the cytoplasm, synthesize proteins for use by the cell itself, and ribosomes associated with the endoplasmic reticulum, produce a protein that is derived from the cell. Various functional proteins are synthesized in ribosomes: proteins-carriers, enzymes, receptors, cytoskeleton proteins.

Machine Golgi. Educated by the tubuine system, tanks and bubbles. It is associated with the endoplasmic reticulum, and the biologically active substances entered here are stored in a compacted form in secretory bubbles. The latter are constantly separated from the Golgi apparatus, transported to the cell membrane and merge with it, and the substances contained in bubbles are derived from the cell in the process of exocytosis.

Lysosomes - Surrounded by a particle membrane of 0.25-0.8 microns. They contain numerous enzymes involved in splitting proteins, polysaccharides, fats, nucleic acids, bacteria and cells.

Peroxisoma Formulated from a smooth endoplasmic reticulum, remind of lysosomes and contain enzymes that catalyzing the decomposition of hydrogen peroxide, which is split under the influence of peroxidase and catalase.

Mitochondria contain outdoor and inner membranes and are the "energy station" of cells. Mitochondria is round or elongated formations with a double membrane. The inner membrane forms protruding inside the mitochondria of folds - cristes. The synthesis of ATP occurs in them, the substrates of the Krebs cycle and a plurality of biochemical reactions are made. ATP molecules formed in mitochondria diffuse in all parts of the cell. The mitochondria contains a small amount of DNA, RNA, ribosomes, and with their participation there is an update and synthesis of new mitochondria.

Microfilaments Present thin protein threads consisting of mip and actin, and form a cage contractual apparatus. Microfilaments are involved in the formation of folds or protrusions of the cell membrane, as well as when moving various structures inside the cells.

Microtubule Make up the basis of the cytoskeleton and ensure its strength. The cytoskeleton gives the cells the characteristic appearance and shape, serves as a place to attach intracellular organelles and various calves. In the nerve cells, the bunches of microtubules participate in the transport of substances from the cell body to the ends of axons. With their participation, the functioning of mitotic spindles during cell division is carried out. They play the role of motor elements in vile and flagella of eukaryotes.

Core It is the main structure of the cell, participates in the transfer of hereditary signs and in the synthesis of proteins. The kernel is surrounded by a nuclear membrane containing a set of nuclear pores through which various substances exchange between the core and the cytoplasm occurs. Inside him is nucleolo. The important role of the nucleoline in the synthesis of ribosomal RNA and protein-histone was established. The remaining parts of the nucleus contains chromatin consisting of DNA, RNA and a number of specific proteins.

Functions of cell membrane

In the regulation of intracellular and intercellular metabolism, cell membranes play a crucial role. They possess election permeability. Their specific structure allows you to provide barrier, transport and regulatory functions.

Barrier function It is manifested in limiting penetration through the membrane dissolved in water compounds. The membrane is impermeable for large protein molecules and organic anions.

Regulatory function Membranes consists in the regulation of intracellular metabolism in response to chemical, biological and mechanical impacts. Various impacts are perceived by special membrane receptors with a subsequent change in enzyme activity.

Transport function Through biological membranes can be carried out passively (diffusion, filtering, osmosis) or with the help of active transport.

Diffusion - Movement of gas or soluble substance at a concentration and electrochemical gradient. The diffusion rate depends on the permeability of the cell membrane, as well as the concentration gradient for uncharged particles, electrical and concentration gradients for charged particles. Simple diffusion It occurs through lipid bilayer or through the channels. Charged particles are moving according to an electrochemical gradient, and uncharged - chemical gradient. For example, oxygen, steroid hormones, urea, alcohol, etc. penetrate the simple diffusion through the lipid layer of the membrane. Various ions and particles are moved through the channels. Ion channels are formed by proteins and are divided into managed and unmanaged channels. Depending on selectivity, ion-selective ropes are distinguished, transmitting only one ion, and channels that do not possess selectivity. Channels have a mouth and a selective filter, and controlled channels - and a portable mechanism.

Light diffusion - The process in which substances are transferred through the membrane using special membrane protein carriers. In this way, amino acids and monosahara penetrate into the cell. This type of transport occurs very quickly.

Osmosis - Water movements through a membrane of a solution with a lower solution with a higher osmotic pressure.

Active transport - Transfer of substances against concentration gradient with the help of transport ATPAZ (ion pumps). This transfer occurs with the cost of energy.

Na + / K + -, Ca 2+ - and N + -Nasos are largely studied. Pumps are located on cell membranes.

A variety of active transport are Endocytosis and exocytosis. With the help of these mechanisms, larger substances (proteins, polysaccharides, nucleic acids) are transported, which cannot be transferred via channels. This vehicle is more common in the epithelial cells of the intestines, renal tubules, endothelium of vessels.

For Endocytosis Cell membranes form piercing inside the cell, which are elapsed, turn into bubbles. With exocytosis, bubbles with content are transferred to the cell membrane and merge with it, and the contents of bubbles are released into the extracellular medium.

The structure and functions of the cell membrane

To understand the processes that ensure the existence of electrical potentials in living cells, first of all, it is necessary to represent the structure of the cell membrane and its properties.

Currently, the liquid-mosaic model of the membrane, proposed by S. Singer and G. Nicholson, in 1972, is used by the membrane, the membrane base is a double layer of phospholipids (broken), the hydrophobic fragments of the molecule of which are immersed in the membrane thickness, and the polar hydrophilic groups are oriented outward, those. in the surrounding aqueous medium (Fig. 2).

Membrane proteins are localized on the surface of the membrane or can be embedded on different depths into the hydrophobic zone. Some proteins permeate the membrane through, and various hydrophilic groups of the same protein are found along both sides of the cell membrane. The proteins found in the plasma membrane play a very important role: they are involved in the formation of ion channels, play the role of membrane pumps and carriers of various substances, and can also perform a receptor function.

The main functions of the cell membrane: barrier, transport, regulatory, catalytic.

The barrier function consists in limiting diffusion through the membrane of water-soluble compounds, which is necessary to protect cells from foreign, toxic substances and conservation within the cells of the relative constant content of various substances. Thus, the cell membrane can slow down the diffusion of various substances at 100,000-10,000,000 times.

Fig. 2. Three-dimensional scheme of liquid-mosaic model Membrane Singer-Nicholson

Show globular integral proteins immersed in lipid bilayer. Part of the proteins is ion channels, other (glycoproteins) contain oligosaccharide side chains involved in each other's cell recognition and in the intercellular tissue. Cholesterol molecules are closely adjacent to phospholipid heads and fix the adjacent areas of "tails". Internal areas of the tails of phospholipid molecule are not limited in their movement and are responsible for the membrane fluidity (Bretskher, 1985)

The membrane contains channels through which ions penetrate. Channels are the potential dependent and potential-dependent. Potential test channels open when changing the difference in potentials, and Potential independent (hormone-controlled) opens when the interaction of receptors with substances. Channels can be open or closed due to goal. Two types of gates are built into the membrane: Activation (in the depths of the channel) and inactivational (on the surface of the channel). The gate can be in one of three states:

open state (both types of gates are open);
closed state (activation gates are closed);
inactivational state (inactivational gates are closed).

Another characteristic feature of the membrane is the ability to carry out the selective transfer of inorganic ions, nutrients, as well as various exchange products. There are systems of passive and active transfer (transport) substances. Passive Transport is carried out through ion channels with or without the help of carrier proteins, and its driving force is the difference of electrochemical potentials of ions between intra and extracellular space. The selectivity of ion channels is determined by its geometrical parameters and the chemical nature of groups, lining channel walls and its mouth.

Currently, channels with selective permeability for Na + ions, K +, Ca 2+ as well as for water (so-called aquaporins) are most well studied. The diameter of the ion channels, according to different studies, is 0.5-0.7 nm. Channel bandwidth may vary, 10 7 - 10 8 ions per second can pass through one ion channel per second.

Active Transportation occurs with the cost of energy and is carried out by the so-called ion pumps. Ion pumps are molecular protein structures embedded in the membrane and carrying out ion transfer to a higher electrochemical potential.

The operation of pumps is carried out due to the energy of hydrolysis of ATP. Na + / k + - ATPase, Ca 2+ - Atthase, H + - Atthase, H + / K + - Atthase, Mg 2+ - Atthase, which ensure the movement of Na + ions, to +, Ca 2+, is currently studied. , H +, Mg 2+ is isolated or conjugate (Na + and K +; H + and K +). The molecular mechanism of active transport is not fully found out.

Cell membrane.
The cell membrane separates the contents of any cell from the external environment, providing its integrity; regulates the exchange between the cell and the medium; Intracellular membranes divide the cell to specialized closed compartments - compartments or organelles in which certain environmental conditions are supported.
Structure.
The cell membrane is a double layer (broken) of lipid class molecules (fats), most of which are so-called complex lipids - phospholipids. Lipid molecules have a hydrophilic ("head") and hydrophobic ("tail") part. When forming membranes, the hydrophobic portions of molecules are turned inside, and hydrophilic - outwards. Membranes - the structures are very similar to different organisms. The membrane thickness is 7-8 nm. (10-9 meters)
Hydrophilicity- The ability of the substance is made water.
Hydrophobity- The inability of the substance is made water.
The biological membrane includes various proteins:
- integral (piercing membrane through)
- semi-integrated (immersed by one end in an external or inner lipid layer)
- surface (located on the outer or adjacent to the inner sides of the membrane).
Some proteins are points of contact of the cell membrane with the cytoskeleton inside the cell, and the cell wall (if there is) is outside.
Cytoskeleton- Cell frame inside the cell.
Functions.
1) Barrier - Provides adjustable, selective, passive and active metabolism with the environment.
2) Transport - Through the membrane, there are vehicles in a cell and from a cell. Similar - ensures a certain interjection and orientation of membrane proteins, their optimal interaction.
3) Mechanical - ensures the autonomy of the cell, its intracellular structures, is also a compound with other cells (in tissues). The intersecting substance has a large role in ensuring a mechanical function.
4) Receptor - Some proteins in the membrane are receptors (molecules, with which the cell perceives certain signals.
For example, hormones circulating in blood apply only to such target cells that have receptors corresponding to these hormones. Neurotransmitters (chemicals that ensure the carrying of nerve pulses) are also associated with special receptor proteins of target cells.
Hormones- biologically active signaling chemicals.
5) Enzymatic - Membrane proteins are often enzymes. For example, plasma membranes of intestinal epithelial cells contain digestive enzymes.
6) the implementation of generation and conduct of biopotentials.
Using the membrane in the cell, a constant concentration of ions is maintained: the concentration of ion K + inside the cell is significantly higher than outside, and the Na + concentration is significantly lower, which is very important, as it ensures that the potential difference on the membrane and the generation of the nerve impulse.
Nervous impulse – the excitation wave transmitted by the nervous fiber.
7) Cell marking - The membrane has antigens acting as markers - "labels", allowing the cell to identify. These are glycoproteins (that is, proteins with branched oligosaccharide side chains attached to them), playing the role of "antennas". Because of the countless side chains configurations, it is possible to make your special marker for each cell type. With the help of cell markers, other cells can recognize and act agreed with them, for example, in the formation of organs and tissues. It allows the immune system to recognize alien antigens.
Features of permeability.
Cell membranes have electoral permeability: they are slowly penetrated in different ways:
Glucose is the main source of energy.

Amino acids - building elements from which all proteins of the body consist.

Fatty acids - structural, energy and other functions.

Glieceol - plants the body to hold water and reduces urine production.

Ions - enzymes for reactions.

Moreover, the membranes themselves actively regulate this process - some substances are missing, and others are not. There are four main mechanism for the admission of substances into a cell or withdrawal of them from the cell outside:
Passive permeability mechanisms:
1) diffusion.
A variant of this mechanism is a lightweight diffusion, in which the substance helps to pass through a diaphragm any specific molecule. This molecule may have a channel that transmits only one type of substances.
Diffusion- The process of mutual penetration of the molecules of one substance between the other molecules.
Osmosis– the process of one-sided diffusion through a semi-permeable membrane of solvent molecules in the direction of a larger concentration of the dissolved substance.
The membrane surrounding the normal blood cell is permeable only for water molecules, oxygen, some of the nutrients dissolved in the blood and cell life products
Active permeability mechanisms:
1) Active transport.
Active transport– movement of a substance from a low concentration area to the area is high.
Active transport requires energy costs, as it comes from the low concentration area to the high area. The membrane exists special proteins - pumps that are actively pumping potassium ions (K +) and pump sodium ions (Na +) from it, ATP serve as energy.
ATF– universal energy source for all biochemical processes. . (More Later)
2) endocytosis.
Particles for any reason are not able to cross the cell membrane, but necessary for the cell can penetrate the membrane by endocytosis.
Endocytosis– the process of capturing the external material by the cell.
The electoral permeability of the membrane under passive transport is due to special channels - integral proteins. They permeate the membrane through, forming a kind of passage. For K, Na and CL elements have their own channels. Regarding the gradient of the concentration of the molecule of these elements move into a cell and from it. When irritating, sodium ion channels are disclosed, and a sharp admission to sodium ions is sharp. At the same time, the imbalance of membrane potential occurs. After that, the membrane potential is restored. Potassium channels are always open, potassium ions slowly fall into the cage.
Structure of membrane
Permeability
Active transport
Osmosis
Endocytosis

The cell membrane is an ultra-thin film on the surface of the cell or cell organelles, consisting of a bimolecular layer of lipids with built-in proteins and polysaccharides.

Membranes functions:

· Barrier - provides adjustable, selective, passive and active metabolism with the environment. For example, the membrane peroxiz protects the cytoplasm from the dangerous peroxide cells. The selective permeability means that the permeability of the membrane for various atoms or molecules depends on their size, electrical charge and chemical properties. Electoral permeability ensures the separation of cells and cell compartments from the environment and the supply of their necessary substances.
· Transport - through the membrane transport substances in a cell and from the cell. Transportation through membranes provides: delivery of nutrients, removal of final exchange products, secretion of various substances, the creation of ion gradients, maintaining the optimal pH and the concentration of ions that are needed for the operation of cell enzymes. Particles for any reason unable to cross the phospholipid bilayer (for example, due to hydrophilic properties, since the membrane inside the hydrophobic and does not pass hydrophilic substances, or due to large sizes), but necessary for the cell can penetrate the membrane through special Proteins-carriers (conveyors) and proteins-channels or by endocytosis. In case of passive transport, the substances crosses the lipid bisel without the cost of energy under the concentration gradient by diffusion. A variant of this mechanism is a lightweight diffusion, in which the substance helps to pass through a diaphragm any specific molecule. This molecule may have a channel that transmits only one type of substances. Active transport requires energy costs, as it happens against the concentration gradient. The membrane exists special proteins - pumps, including atpase, which actively pumps potassium ions in the cell (K +) and pump sodium ions (Na +) from it.
· Matrix-- provides a certain interjection and orientation of membrane proteins, their optimal interaction.
· Mechanical-- ensures the autonomy of the cell, its intracellular structures, also connect to other cells (in tissues). Cell walls have a large role in ensuring mechanical function, and in animals-- intercellular substance.
· Energy-- with photosynthesis in chloroplasts and cellular breathing in mitochondria in their membranes there are energy transfer systems in which proteins also participate;
· Receptor-- Some proteins that are in the membrane are receptors (molecules, with which the cell perceives certain signals. For example, hormones circulating in blood apply only to such target cells that have receptors corresponding to these hormones. Neurotransmitters (chemicals that ensure the carrying of nerve pulses) are also associated with special receptor proteins of target cells.
· Enzymatic - membrane proteins are often enzymes. For example, plasma membranes of intestinal epithelial cells contain digestive enzymes.
· Implementation of generation and conduct of biopotentials. Using the membrane in the cell, a constant concentration of ions is maintained: the concentration of ion K + inside the cell is significantly higher than outside, and the Na + concentration is significantly lower, which is very important, as it ensures that the potential difference on the membrane and the generation of the nerve impulse.
· Cell marking-- on the membrane there are antigens acting as markers-- "labels", allowing you to identify the cell. These are glycoproteins (that is, proteins with branched oligosaccharide side chains attached to them), playing the role of "antennas". Because of the countless side chains configurations, it is possible to make your special marker for each cell type. With the help of cell markers, other cells can recognize and act agreed with them, for example, in the formation of organs and tissues. It allows the immune system to recognize alien antigens.

Some protein molecules are freely diffused in the plane of the lipid layer; In the usual state of the protein molecules, which overlook the different sides of the cell membrane, do not change their position.

Special morphology of cell membranes determines their electrical characteristics, among which the container and conductivity are the most important.

Capacitive properties are mainly determined by phospholipid bislock, which is impenetrable for hydrated ions and at the same time sufficiently thin (about 5 nm) to ensure efficient separation and accumulation of charges, and electrostatic interaction of cations and anions. In addition, the capacitive properties of cell membranes are one of the reasons that determine the time characteristics of the electrical processes occurring on cell membranes.

Conductivity (G) is the value of electrical resistance and equal to the ratio of the total transmembrane current for a given ion to the magnitude that determined its transmembrane potential difference.

Through phospholipid bilay, various substances can diffuse, and the degree of permeability (P), i.e., the ability of the cell membrane to pass these substances depends on the difference in the concentrations of the diffusant substance along both sides of the membrane, its solubility in lipids and properties of the cell membrane. The diffusion rate for charged ions under the conditions of a constant field in the membrane is determined by the mobility of ions, the thickness of the membrane, the distribution of ions in the membrane. For non-electrolytees, the permeability of the membrane does not affect its conductivity, since non-electrolytes do not bear charges, i.e. cannot bear the electric current.

The conductivity of the membrane is a measure of its ion permeability. An increase in conductivity indicates an increase in the number of ions passing through the membrane.

An important property of biological membranes - fluidity. All cell membranes are movable fluids: most of the components of their lipid molecules and proteins are capable of moving enough to move in the membrane plane

The cell membrane is a structure covering the cell outside. It is also called a cytlemma or plasmolem.

This formation is constructed from a bilipid layer (bilayer) with proteins embedded in it. Carbohydrates included in the plasmolemma are in the associated state.

The distribution of the main components of the plasmolm is as follows: more than half of the chemical composition fall on proteins, a quarter occupy phospholipids, the tenth part - cholesterol.

Cell membrane and its types

The cell membrane is a thin film, which is the basis of the layers of lipoproteins and proteins.

The localization is distinguished by membrane organelles, having some features in plant and animal cells:

mitochondria;
core;
endoplasmic reticulum;
golgi complex;
lysosomes;
chloroplasts (in vegetable cells).

There is also an internal and outer (plasmolm) cell membrane.

The structure of the cell membrane

The cell membrane contains carbohydrates that cover it in the form of glycicalis. This is a supermarket structure that performs a barrier function. Proteins located here are in a free state. Unbound proteins are involved in enzymatic reactions, providing extracellular splitting of substances.

The cytoplasmic membrane proteins are represented by glycoproteins. By chemical composition, proteins included in the lipid layer are completely (all over) - integral proteins. Also peripheral, not reaching one of the surfaces of plasmolemma.

The first functions as receptors, binding to neurotransmitters, hormones and other substances. Insert proteins are necessary for the construction of ion channels through which the ions transportation, hydrophilic substrates are carried out. The second are enzymes catalyzing intracellular reactions.

The main properties of the plasma membrane

Lipid Bilayer prevents water penetration. Lipids - hydrophobic compounds represented in phospholipid cell. The phosphate group is turned out and consists of two layers: an outer, aimed at extracellular medium, and internal, excavating intracellular content.

Water soluble sections are called hydrophilic heads. Sections with fatty acid are directed inside the cell, in the form of hydrophobic tails. The hydrophobic part interacts with adjacent lipids, which ensures their attachment to each other. The double layer has election permeability in different sections.

Thus, in the middle of the membrane impermeable for glucose and urea, hydrophobic substances are published here: carbon dioxide, oxygen, alcohol. Cholesterol is important, the content of the latter determines the viscosity of the plasmolemma.

Functions Outdoor Membranes Cells

Function characteristics are briefly listed in Table:

Membrane function	Description
Barrier role	Plasmolymma performs a protective function, preventing the contents of the cell from the effects of alien agents. Due to the special organization of proteins, lipids, carbohydrates, plasmalym is provided.
Receptor function	Through the cell membrane, biologically active substances are activated in the process of binding to receptors. Thus, immune reactions are mediated through the recognition of alien agents by the receptor cell of the cells localized on the cell membrane.
Transport function	The presence of pores in plasmolem allows you to regulate the admission of substances inside the cell. The transfer process proceeds passively (without energy costs) for compounds with low molecular weight. Active transfer is associated with the cost of energy released during the splitting of adenosyntriphosphotus (ATP). This method takes place to transfer organic compounds.
Participation in digestive processes	At the cell membrane, substances are precipitated (sorption). Receptors are associated with a substrate by moving it inside the cell. A bubble is formed, freely lying inside the cell. Merging, such bubbles form lysosomes with hydrolytic enzymes.
Enzymatic function	Enzymes needed components of intracellular digestion. Reactions requiring catalyst participation proceed with the participation of enzymes.

What value is the cell membrane

The cell membrane participates in maintaining homeostasis due to the high selectivity of incoming and exiting substances from the cell (in biology it is called the election permeability).

Plasmolm grows are separated by a cell to compartments (compartments) responsible for performing certain functions. Specificly arranged membranes corresponding to the liquid-mosaic scheme ensure the integrity of the cell.

The cell membrane is one of the most important organoids, which serves as a kind of barrier between this cell and the external environment. Scientific names are plasmalamic, cytlemma or plasma membrane. It is through it that the cell interaction with an external environment occurs, the nutrients fall through it inside, and the outward is allocated that what has already been processed. Plasmamama has a rather complex structure, and also performs many functions in the body. This article will discuss the cell membrane and its structure in detail.

This organoid was discovered relatively recently, only at the beginning of the twentieth century. The discovery was made by German scientists - a gorter and Grendel. During the entire previous century, scientists were actively studied by the cytlemma, various theories were put forward on its structure, which eventually refuted, and new ones were entering their place. And only for the seventies, scientists were able to reliably determine its structure.

So what is the cell membrane? Through numerous studies it was found that it has three layers in its composition. The upper and lower layers are unparalleled areas of associations of protein molecules, and the inner layer, on the contrary, a solid, consisting of fats, is the main one, due to it is insulation from the external environment. The fat layer includes two rows of lipids (otherwise it is called - bilipid).

The cytlemma presents the following types of lipids:

phospholipids (fats and phosphorus);
glycolipids (fats and carbohydrates);
cholesterol.

The protein outer and inner layers serve so that substances that cannot penetrate inside through the fat layer can get there according to the strata, that is, they are "crossops" for soluble substances.

So, the cell membrane is formed by three levels, two of which are peculiar conveyors for substances that cannot penetrate the third level, which is the main, this is the barrier that isolates the internal content, but also provides connection with other cells, After all, it is through it that the main amount of nutrients falls inside.

It is also important to understand that the cell membrane and cell wall are different organides. There are many differences, and they are essential, the wall is over the cythemma, serves as protection against mechanical damage and pressure. The functions of the cytlemma, in turn, are in the other.

Watch the video about the cell membrane and its functions.

The functions of the cell membrane include:

Barrier. It serves as a natural filter for molecules that are going to penetrate inside, it passes only those of them that meet certain parameters.
Protective. Since most animals have no cell wall, the plasmalamma is also protected from mechanical effects and prevents damage. The cell membrane in the plant cell does not perform such a function, since plant cells have a sophisticated wall, which is capable of protecting them.
Matrix. Responsible for the location of internal organides relative to each other to maintain the internal balance required for full-fledged activities.
Transport. Fully controls the exchange of necessary substances with the external environment, it helps thanks to the special features of those that are necessary for life, but at the same time, cannot independently penetrate inside.
Enzymatic. Need to generate enzymes, necessary, for example, to digest food.
Receptor. It is necessary for making signals talking about what is happening in the external environment.
Marking. Each cell is unique, and cells can recognize each other, it is necessary in order to interact with each other. Recognition occurs due to the building of the cytlemma, which is not repeated.

The cytlemmas of any living beings are in the essence of the same number of functions, only with small variations, regardless of whether the cytlem is considered: an animal, man, insect or a cell membrane of the plant.

Conclusions about PlasmaMalem

Having considered the structure and functions of this organo, it can be noted that the cell membrane possesses features not characteristic of other cell components. The opening of it at the beginning of the last century contributed to the further development of medicine, served as a key to understanding the many human diseases, as well as the methods of their treatment.

The cell membrane is characteristic of the cells of each organism. It serves as protection, and also performs very important functions, because through it various substances penetrate inside. In order for this organoid to function normally, and, therefore, that the cell as a whole can function normally, it is necessary that such conditions that do not interfere with its activities are maintained.

As is known, the plasma membrane, its structure is a variety of channels, due to which the exchange with the external environment is ensured. Scientists have been found out that for normal functioning, in particular, so that the cell does not start turnbuses into the cancer, it is necessary that the plasma-standing channels work properly not clogged, they did not miss unsuitable molecules.

proper nutrition;
regular walks in the fresh air;
maintaining the water balance of the body.

It is amazing, but it was exactly that it would seem, a minor organoid can strongly influence the well-being of a person and his health. Therefore, the opening of Plasmama was a huge step forward for biological science.

Do you think the cell membrane plays the most important role in the functioning of the cell or have more important components? Share your opinion in