What is a membrane? This concept is used in various life spheres and sciences. Moreover, in each of them it has a different meaning. But, one way or another, the use of this term is associated with the meaning of the word itself. Translated from Latin, “membrane” is a membrane.
Different interpretations of the concept
In technology and engineering, this concept is used when talking about a thin film or plate fixed along the contour, as in microphones or manometers.
In biology, under the membrane is meant an elastic molecular structure that exists in every cell and performs the function of protecting against environmental influences. It provides cell integrity and is involved in metabolic processes with the outside world.
Reverse osmosis membrane
One recent invention is the reverse osmosis module, which is used to purify water. This design is a pipe having a bottom and a cover. And inside this pipe is just the reverse osmosis membrane, the presence of which ensures the production of ultrapure water, freed from various bacteriological contaminants and biological deposits. The liquid purification mechanism is based on minimizing dead spaces in which bacteria can accumulate.
These modules are widely used in medicine, and to be more precise, they supply hemodialysis devices with ultrapure water.
Membrane accumulators and expansion tanks. Their replacement
Hydraulic accumulators and expansion tanks are devices that are used to compensate for excess pressure (volume) inside heating devices.
What is a membrane in this case? This element is the main component of devices of this type. It affects the performance and reliability of the entire system. The membrane may vary in shape. It happens diaphragm, spherical and balloon. If the tank has a large volume, then a metal fitting is inserted into the back of the element, in which there is an opening for bleeding air. Depending on the scope of use of the device, material is selected for the manufacture of the membrane. For example, in the expansion tanks of the heating system, the main criterion is the level of heat resistance and durability. In the case of cold water supply, when choosing the material of the membrane, they are guided by the criterion of dynamic elasticity.
Unfortunately, there is no material that could be called universal. Therefore, his correct choice is one of the most important conditions for long-term operation of the device and its effective operation. Most often, the plates are made of natural rubber, synthetic butyl or ethylene propylene rubber.
The membrane is replaced by disconnecting the accumulator or expansion tank from the system. First, the screws that fasten the flange and housing are disconnected. In some devices there is also a mount in the nipple area. After removing it, the membrane can be easily removed. By performing reverse actions, you need to put a new membrane.
Polymer membranes
The term "polymer membrane" is used in several cases. Firstly, it is used to talk about one of the most modern and advanced roofing materials in terms of practicality. This type of membrane is produced by applying the extrusion method, ensuring the absence of voids in the composition of the finished material. The advantages of a polymer product include absolute waterproofness, vapor permeability, low weight, strength, low flammability, environmental safety.
The term "polymer membrane" is often used when it comes to the above-mentioned reverse osmosis plates, as well as other types of shells made from organic polymers. These are micro and ultrafiltration products, membranes used in nanofiltration. The advantage of polymer membranes in this context lies in their high technological effectiveness and great possibilities of controlling the properties and structure of the material. In this case, small chemical and technological variations of the manufacturing process are used.
Cell membrane. Cells - units of all living things
It has long been known that the basic structural unit of a living organism is a cell. It is a differentiated region of the cytoplasm, which is surrounded by a cell membrane. In the process of evolution, with the expansion of the limits of functionality, it acquired plasticity and subtlety, because the most important processes in the body occur precisely in the cells.
The cell membrane is the border of the cell, which is a natural barrier between its internal contents and the environment. The main characteristic feature of the membrane is its semi-permeability, which ensures the penetration of moisture and nutrients into the cell and the removal of decay products from it. The cell membrane is the main structural component of cell organization.
Historical facts related to the discovery and investigation of the cell membrane
In 1925, Grendel and Gorder successfully performed an experiment to identify the "shadows" of red blood cells. It was they who, in the course of the experiments, first discovered the lipid bilayer. The successors of their work, Danielle, Dawson, Robertson, Nicholson in different years worked on creating a liquid-mosaic model of the membrane structure. Finally, Singsher managed to do this in 1972.
The main functions of the cell membrane
- Separation of the internal contents of the cell from the components of the external environment.
- Contributing to maintaining a consistent chemical composition within the cell.
- Regulation of the balance of metabolism.
- Ensuring interconnection between cells.
- Signal function.
- Protective function.
Plasma shell
What is a membrane called a plasma membrane? This is the outer cell wall, which in its structure is an ultramicroscopic film with a thickness of 5-7 nanomillimeters. Its composition includes protein compounds, phospholipids, water. The film, being very flexible, absorbs moisture well, and also has the ability to restore its integrity with rapid speed.
The plasma membrane is characterized by a universal structure. Its boundary position determines the participation in the process of selective permeability during the removal of decay products from the cell. Interacting with neighboring elements and reliably protecting the contents from damage, the outer membrane is one of the most important components of the cell structure.
The thinnest layer that sometimes covers the cell membrane of living organisms is called glycocalyx. It consists of proteins and polysaccharides. And in plant cells, the membrane is protected from above by a special wall, which also performs a supporting function and maintains its shape. It mainly consists of fiber - an insoluble polysaccharide.
Thus, we can conclude that the main functions of the outer cell membrane are restoration, protection, and interaction with neighboring cells.
Structural features
What is a membrane? This is a movable shell, the width of which is 6-10 nanomillimeters. The basis of its structure is the lipid bilayer and proteins. Carbohydrates are also present in the membrane, but they account for only 10% of the mass of the membranes. But they are mandatory in glycolipids or glycoproteins.
If we talk about the ratio of the number of proteins and lipids, then it can vary greatly. It all depends on the type of fabric. For example, myelin contains about 20% protein, and mitochondria - about 80%. The composition of the membrane directly affects its density. The higher the protein content, the higher the density of the shell.
The variety of lipid functions
Each lipid is inherently a phospholipid, resulting from the interaction of glycerol and sphingosine. Around the lipid skeleton are membrane proteins, but their layer is not continuous. Some of them are immersed in a layer of lipids, while others seem to permeate it. This is due to the presence of areas permeable to water.
It is obvious that the composition of lipids in various membranes is not random, but no clear explanation for this phenomenon has yet been found. Up to one hundred different types of lipid molecules can be contained in any particular membrane. Consider the factors that may affect the determination of the lipid composition of the membrane molecule.
- Firstly, a lipid mixture must necessarily have the ability to form a stable bilayer in which proteins can function.
- Secondly, lipids should help stabilize severely deformed membranes, establish contact between the membranes, or bind certain proteins.
- Thirdly, lipids are bioregulators.
- Fourth, some lipids are active participants in biosynthesis reactions.
Cell membrane proteins
Proteins perform several functions. Some play the role of enzymes, while others transport various substances from the environment into the cell and vice versa.
The structure and functions of the membrane are designed in such a way that integral proteins penetrate it through, providing a close connection. But peripheral proteins are not too closely associated with the membrane. Their function is to maintain the structure of the shell, receive and convert signals from the external environment, and also serve as catalysts for various reactions.
The composition of the membrane is represented primarily by the bimolecular layer. Its continuity provides the barrier and mechanical properties of the cell. During the life process, a violation of the structure of the bilayer can occur, which leads to the formation of structural defects of through hydrophilic pores. Following this, all functions of the cell membrane may be impaired.
Shell Properties
Features of the cell membrane are due to its fluidity, due to which it does not have a rigid structure. The lipids that make up its composition can move freely. Asymmetry of the cell membrane can be observed. This is the reason for the difference in the composition of the protein and lipid layers.
The polarity of the cell membrane is proved, that is, its outer side has a positive charge, and the inner one is negative. It should also be noted that the shell has selective insight. In addition to water, it passes only certain groups of molecules and ions of dissolved substances.
Features of the structure of the cell membrane in plant and animal organisms
The outer membrane and the endoplasmic reticulum of the cell are closely connected. Often the surface of the shell is also covered with various protrusions, folds, microvilli. The plasma membrane of the cells of animals is externally coated with a glycoprotein layer that performs receptor and signaling functions. In plant cells, outside this shell is another, thick and distinctly visible under a microscope. Fiber, of which it consists, is involved in the formation of support in tissues of plant origin, for example, wood.
Animal cells also have external structures located outside the membrane. They perform an exclusively protective function. An example is chitin, which is found in the integumentary tissue of insects.
In addition to the cell, there is an intracellular, or internal membrane. It divides the cell into specialized enclosed compartments called organelles. They must constantly maintain a certain environment.
Based on the foregoing, we can conclude that the cell membrane, whose characteristics prove its importance in the functioning of the whole organism, has a complex composition and structure, depending on many internal and external factors. Damage to this film can lead to cell death.
Thus, the structure and functions of the membrane depend on the field of science or industry, in which this concept is applied. In any case, this element is a shell or partition, which has flexibility and is fixed at the edges.