The functions of the plasma membrane in a cell

plasma membrane - lipid bilayer with embedded in its thickness proteins, ion channels and receptor molecules.It is a mechanical barrier that separates the cytoplasm from the pericellular space, simultaneously being the only link with the outside.And because cytolemma is one of the most important structures of the cell and its functions allow it to exist and interact with other cellular groups.

Understanding functions tsitolemmy

plasma membrane in the form in which it is present in an animal cell, characterized for a variety of organisms from different kingdoms.Bacteria and protozoa, whose body are of a single cell, are the cytoplasmic membrane.And animals, fungi and plants as the multicellular organisms have not lost it in the course of evolution.However, the different kingdoms of living organisms tsitolemmy somewhat different, although its function is still the same.They can be divided into three groups: dividing, transport and communication.

The group dividing functions include mechanical protection cells, maintaining its shape, protection from the extracellular medium.Transport Group functions of the membrane plays due to the presence of specific proteins, ion channels and transporters of certain substances.By the communicative function is attributed tsitolemmy receptor.On the surface there is a set of membrane receptor complexes, by which cells are involved in the mechanisms of humoral transmission.However, it is also important that cytolemma surrounds not only the cell, but also some of its membrane organelles.In them it plays the same role as in case of the whole cell.

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barrier function

barrier function of the plasma membrane of multiple.It protects the internal environment of the cell with the current concentration of the chemicals from its changes.The solution is the process of diffusion, that is self-leveling concentrations between media with different content of certain substances.Plasmolemma just blocked by preventing the diffusion of ions and fluid flow in any direction.Thus, the membrane restricts the cytoplasm of certain electrolyte concentrations pericellular environment.

second manifestation of the barrier function of the plasma membrane - it is protection from strong acid and strong alkaline environments.Plasmolemma constructed such that the hydrophobic lipid ends of the molecules face outward.Because it is often separates the intracellular and extracellular medium with different pH.It is necessary for cell activity.

barrier function of membrane organelles

barrier function of the plasma membrane are different because they depend on its location.In particular karyotheca, ie lipid bilayer core, protects it from mechanical damage and shared environment from nuclear cytoplasmic.Moreover, it is believed that karyotheca inextricably linked with the membrane of the endoplasmic reticulum.Because the entire system is one considered as a repository of genetic information, protein synthesizing system and a cluster of post-translational modification of protein molecules.Cytoplasmic membrane networks necessary to maintain the form of intracellular transport channels through which move the protein, lipid and carbohydrate molecules.

mitochondrial membrane protects the mitochondria and plastid - chloroplasts.Lysosomal membrane also acts as a barrier: within lysosomes aggressive medium pH and reactive oxygen species that can damage the structures inside cells if they are to penetrate.The membrane is a universal barrier, at the same time permitting the lysosomes to "digest" the solid particles and limits the place of action of enzymes.

mechanical function plasmolemma

mechanical function of the plasma membrane is also not uniform.Firstly, cytolemma supports cell shape.Second, it limits the deformability of cells, but does not prevent the change of form and strength.Thus strengthening the membrane is also possible.This is due to the formation of the cell wall protists, bacteria, plants and fungi.In animals, including at the human species, the cell wall is the simplest and is represented by a glycocalyx.

Bacteria she glycoprotein, plants - cellulose, fungi - chitin.Diatoms and completely inserted in its cell wall of silica (silicon oxide), which significantly increases the strength and mechanical stability of the cell.And every body cell wall is necessary for this.A cytolemma itself has a much lower strength than the layer of proteoglycans, cellulose or chitin.That tsitolemmy plays a mechanical role, no doubt.

also mechanical functions of the plasma membrane allow the mitochondria, chloroplasts, lysosomes, nucleus and endoplasmic reticulum within the cell to function and defend against subthreshold damage.This is true for any cell having a membrane organelles data.Moreover, the plasma membrane is cytoplasmic protuberances, which are generated by cell-cell contacts.This embodiment of the mechanical function of the plasma membrane.The protective role of the membrane is ensured even at the expense of natural resistance and fluidity of the lipid bilayer.

communicative function of the cytoplasmic membrane

Among communicative functions should include the transport and reception.These two qualities are specific to the plasma membrane and karyotheca.The membrane organelles not always riddled with receptors or transport channels, and at karyotheca tsitolemmy and these formations there.It is being implemented by means of data communication functions.

Transport is realized by two possible mechanisms: a loss of energy, that is, an active way, and without the cost, simple diffusion.However, the cell can be transported substances and by phagocytosis or pinocytosis.This is accomplished by capturing a cloud of liquid or solid particles protrusions cytoplasm.Then the cell as if the hands captures particles or droplets of liquid, pulling her inside and forming around the cytoplasmic layer.

active transport, diffusion

Active transport - is an example of selective absorption of electrolytes and nutrients.Via specific channels represented by protein molecules composed of several subunits substance or hydrated ion penetrates into the cytoplasm.Jonah changing potentials and nutrients are embedded in the metabolic chain.All these features of the plasma membrane in a cell actively contribute to its growth and development.

lipid soluble

highly differentiated cells, such as the nervous, endocrine and muscle use these ion channels to generate the potentials of peace and action.It is formed by osmotic and electrochemical differences, and gain the ability to shrink the tissue to generate or conduct impulse to respond to signals and transmit them.This is an important mechanism for the exchange of information between the cells, which is the basis of the nervous regulation of the functions of the whole organism.These functions of the plasma membrane of animal cells provide the regulation of vital functions, protection and movement of the whole body.

Some substances at all can penetrate through the membrane, but it is characteristic only for lipophilic molecules of fat-soluble molecules.They are simply dissolved in the bilayer membrane is easily entering the cytoplasm.This transport mechanism is characteristic of steroid hormones.A structure of the peptide hormones are unable to penetrate through the membrane, while also transmit cell information.This is achieved due to the presence of the receptor on the surface of plasmolemma (integrated) molecules.The related biochemical mechanisms of signal transduction to the nucleus together with the mechanism of direct penetration of substances through the lipid membrane is a simple system of humoral regulation.All these functions integral plasma membrane proteins requires not only a single cell and whole organism.

Table functions of the cytoplasmic membrane

most intuitive way to scroll to the plasma membrane - a table which contains its biological role in the cell as a whole.



biological role

cytoplasmic membrane in the form of a lipid bilayer with spaced laterally hydrophobic ends equipped receptor complex of integral and surface proteins


support cell shape, protects against mechanical subliminal influences, maintains cellular integrity


transports liquid droplets and solid particles, molecules and hydrated ions into the cell with the cost orwithout the cost of energy


has on its surface receptor molecules that serve to transmit information to the nucleus


By protrusions cytoplasm neighboring cells make contact with each other


provides conditions for the generation of the action potential and resting potential of excitable tissues

The table clearly shows which functions are performed by the plasma membrane.However, these roles are played by only the cell membrane, i.e. the lipid bilayer surrounding the entire cell.Inside it, there are organelles, which also have membrane.Their role should be expressed as a diagram.

plasma membrane functions: circuit

in cell membranes characterized by the presence of the following organelles: the nucleus, rough and smooth endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, lysosomes.In each of these organelles membrane plays a crucial role.Consider the example it can be a table schema.

organelles and membrane


biological role

kernel, nuclear membrane


mechanical function of the plasmamembrane cytoplasm nucleus allow to maintain its shape, prevents structural damage


Separation of nucleoplasm and cytoplasm


has transport pores to exit the ribosome and the mRNA from the nucleus andadmission into nutrients, amino acids and nitrogenous bases

mitochondria, mitochondrial membrane


maintain the shape of mitochondria, an obstacle to mechanical damage


through the membrane passed ionsand energy substrates


Provides generate transmembrane potential that lies at the heart of energy production in the cell

chloroplast membrane of plastids


maintain the shape of plastids,warns of mechanical damage


Provides transport of substances

endoplasmic reticulum, a membrane network

Mechanical and environment-forming

Enforces cavity where the flow processes of protein synthesis andtheir post-translational modification

Golgi apparatus, membrane vesicles and cisterns

Mechanical and environment-forming

role cm. above

lysosomes, lysosomal membranes



Maintaining form lysosomes, preventing mechanical damage and release of enzymes into the cytoplasm, the restriction of its political systems

animal cell membranes

These function in the cell plasma membrane, where it plays an important role for each organelle.Moreover, a number of functions should be merged into one - in protective.In particular barrier and mechanical functions into protective.Moreover, the functions of the plasma membrane of the plant cell are virtually identical to those in animal and bacterial.

animal cell is the most complex and highly differentiated.There is much more integrated, poluintegralnyh and surface proteins.In general, the structure of the membrane of multicellular organisms is always more difficult than that of single-celled.And what most of the plasma membrane of specific cells, determines whether it is classified as epithelial, connective tissue, or excitable.