What are membranes? Biological membrane: functions and structure

Nature has created many organisms and cells, but despite this, the structure and most of the functions of biological membranes are the same, which allows us to consider their structure and study their key properties without attachment to a specific type of cell.

What is a membrane?

Membranes are a protective element that is an integral component of the cells of any living organism.

The structural and functional unit of all living organisms on the planet is the cell. Its vital activity is inextricably linked with the environment with which it exchanges energy, information, and matter. So, the nutritional energy necessary for the functioning of the cell comes from outside and is spent on the implementation of its various functions.

The structure of the simplest structural unit of a living organism: cell membrane , nucleus, organelles, various inclusions. It is surrounded by a membrane, inside of which there is a nucleus and all organelles. These are mitochondria, lysosomes, ribosomes, Golgi apparatus, endoplasmic reticulum. Each structural element has its own membrane.

Role in cell life

The biological membrane plays a climactic role in the structure and functioning of the elementary living system. Only a cell surrounded by a protective membrane can rightfully be called an organism. A process such as metabolism is also carried out due to the presence of a membrane. If its structural integrity is violated, this leads to a change in the functional state of the organism as a whole.

Cell membrane and its functions

It separates the cytoplasm of the cell from the external environment or from the membrane. The cell membrane ensures the proper performance of specific functions, the specificity of intercellular contacts and immune manifestations, and supports the transmembrane difference in electrical potential. It contains receptors capable of perceiving chemical signals - hormones, mediators and other biological active components. These receptors give her yet another ability - to change the metabolic activity of the cell.

Membrane Functions:

1. Active transport of substances.

2. Passive transport of substances:

2.1. Diffusion is simple.

2.2. Pore ​​transfer.

2.3. Transport carried out due to the diffusion of the carrier together with the membrane substance or through the transfer of the relay through the substance along the molecular chain of the carrier.

3. The transfer of non-electrolytes due to simple and facilitated diffusion.

4. Active transport of ions.

The structure of the cell membrane

The component membranes of the cell are lipids and proteins.

Lipids: phospholipids, phosphatidylethanolamine, sphingomyelin, phosphatidylinositol and phosphatidylserine, glycolipids. The proportion of lipids is 40-90%.

Proteins: peripheral, integral (glycoproteins), spectrin, actin, cytoskeleton.

The main structural element is a double layer of phospholipid molecules.

Roofing membrane: definition and typology

Some statistics. In the Russian Federation, a membrane has been used as a roofing material not so long ago. The proportion of membrane roofs from the total number of soft roof ceilings is only 1.5%. Bituminous and mastic roofs are more widespread in Russia. But in Western Europe, membrane roofs account for 87%. The difference is palpable.

As a rule, the membrane as the main material when covering the roof is ideal for flat roofs. For those with a large bias, it is less suitable.

The volumes of production and sale of membrane roofs in the domestic market have a positive growth trend. Why? The reasons are more than clear:

• The service life is about 60 years. Imagine, only the warranty period of use, which is established by the manufacturer, reaches 20 years.
• Easy to install. For comparison: installing a bitumen roof takes 1.5 times longer than installing a membrane ceiling.
• Ease of maintenance and repair work.

The thickness of the roofing membranes can be 0.8-2 mm, and the average weight of one square meter is 1.3 kg.

Properties of roofing membranes:

• elasticity;
• strength;
• resistance to ultraviolet rays and other aggressive media;
• frost resistance;
• fire resistance.

The roofing membrane is of three types. The main classification feature is the type of polymer material that makes up the base of the canvas. So, roofing membranes are:

• EPDM. Membranes belonging to the EPDM group are made on the basis of polymerized ethylene-propylene-diene-monomer, or, more simply, synthetic rubber. Advantages: high strength, elasticity, water resistance, environmental friendliness, low cost. Disadvantages: adhesive technology for joining canvases through the use of a special tape, low strength indicators. Scope: used as a waterproofing material for tunnel ceilings, water sources, waste storage, artificial and natural reservoirs, etc.
• PVC membranes. These are casings in the production of which polyvinyl chloride is used as the main material. Advantages: resistance to ultraviolet, refractoriness, extensive color gamut of membrane paintings. Disadvantages: low resistance to bitumen materials, oils, solvents; emits harmful substances into the atmosphere; the color of the canvas fades over time.
• TVET. Made from thermoplastic olefins. They can be reinforced and unreinforced. The former are equipped with a mesh of polyester or fiberglass fabric. Advantages: environmental friendliness, durability, high elasticity, temperature resistance (both at high and at low temperatures), welded joints of canvas seams. Disadvantages: high price category, lack of manufacturers in the domestic market.

Profiled membrane: characteristics, functions and advantages

Profiled membranes are an innovation in the construction market. Such a membrane is used as a waterproofing material.

The substance used in the manufacture is polyethylene. The latter is of two types: high pressure polyethylene (LDPE) and low pressure polyethylene (HDPE).

The profiled membrane made of high pressure polyethylene has a special surface - hollow bumps. The height of these formations can vary from 7 to 20 mm. The inner surface of the membrane is flat. This makes it possible to smoothly bend the building material.

Changing the shape of individual sections of the membrane is excluded, since the pressure over its entire area is evenly distributed due to the presence of the same protrusions. Geomembrane can be used as ventilation insulation. In this case, free heat exchange inside the building is ensured.

The advantages of profiled membranes:

• increased strength;
• heat resistance;
• resistance to chemical and biological effects;
• long term of operation (more than 50 years);
• ease of installation and maintenance;
• affordable cost.

Profiled membranes come in three types:

• with a single layer of cloth;
• with a two-layer cloth = geotextile + drainage membrane;
• with a three-layer canvas = slippery surface + geotextile + drainage membrane.

A single-layer profiled membrane is used to protect the main waterproofing, installation and dismantling of concrete preparation of walls with high humidity. A two-layer protective is used when equipping wall drainage. Consisting of three layers is used on the soil, which lends itself to frosty heaving, and soil soil located deep.

Scope of use of drainage membranes

The profiled membrane is used in the following areas:

1. Basic foundation waterproofing. Provides reliable protection against the damaging effects of groundwater, plant root systems, soil subsidence, mechanical damage.
2. Wall drainage foundation. It neutralizes the effects of groundwater and precipitation by transporting them to drainage systems.
3. Horizontal reservoir type drainage - protection against deformation due to structural features.
4. An analogue of concrete preparation. It is used in the case of construction work on the construction of buildings in the zone of low groundwater, in cases where horizontal waterproofing is used to protect against capillary moisture. Also, the function of the profiled membrane includes the passage of cement milk into the soil.
5. Ventilation of wall surfaces with increased humidity. It can be installed both on the inside and on the outside of the room. In the first case, air circulation is activated, and in the second, optimal humidity and temperature are ensured.
6. Used inverse roof.

Super diffusion membrane

The superdiffusion membrane is a new generation of material, the main purpose of which is to protect the elements of the roof structure from wind phenomena, precipitation, steam.

The production of protective material is based on the use of non-woven substances, high-quality dense fibers. Three-layer and four-layer membranes are popular in the domestic market. The reviews of specialists and consumers confirm that the more layers underlie the structure, the stronger its protective functions, and hence the higher the energy efficiency of the room as a whole.

Depending on the type of roof, the features of its construction, climatic conditions, manufacturers recommend giving preference to one or another type of diffusion membrane. So, they exist for pitched roofs of complex and simple structures, for pitched roofs with a minimum slope, for roofs with a fold coating, etc.

The superdiffusion membrane is laid directly on the heat-insulating layer, the flooring is made of boards. There is no need for a ventilation gap. The material is fastened with special brackets or steel nails. The edges of the diffusion sheets are connected by a mounting tape. Installation works are allowed to be carried out even under extreme conditions: on a frosty morning, with strong gusts of wind, etc.

In addition, the coating in question can be used as a temporary roof overlap.

PVC membranes: essence and purpose

PFC membranes are roofing materials made from polyvinyl chloride and have elastic properties. Such modern roofing material completely replaced bituminous rolled analogues, which have a significant drawback - the need for systematic maintenance and repair. Today, the characteristic features of PVC membranes make it possible to use them when carrying out repairs on old flat roofs. They are used in the installation of new roofs.

A roof made of such a material is convenient in operation, and its installation is possible on any type of surface, at any time of the year and under any weather conditions. PVC membrane has the following properties:

• strength;
• stability when exposed to UV rays, various kinds of precipitation, point and surface loads.

Thanks to its unique properties, PVC membranes will serve you faithfully for many years. The term of use of such a roof is equal to the term of operation of the building itself, while rolled roofing materials need regular repair, and in some cases completely dismantle and install a new ceiling.

Between each other, PVC membrane sheets are connected by a hot breath welding method, the temperature of which is in the range of 400-600 degrees Celsius. Such a connection is absolutely tight.

Benefits of PVC Membranes

Their advantages are obvious:

• the flexibility of the roofing system, which is most consistent with the construction project;
• strong, tight-fitting connecting seam between the membrane sheets;
• ideal tolerance of climate change, weather, temperature, humidity;
• increased vapor permeability, which contributes to the evaporation of moisture accumulated in the under-roof space;
• many color options;
• fire fighting properties;
• the ability to preserve the initial properties and appearance for a long period;
• PVC membrane is an absolutely environmentally friendly material, which is confirmed by relevant certificates;
• the installation process is mechanized, so it does not take much time;
• operating rules allow the installation of various architectural additions directly on top of the membrane PVC roof itself;
• single-layer styling will save you money;
• ease of maintenance and repair.

Membrane fabric

The textile industry has known membrane fabric for a long time. From such material shoes and clothes are made: adult and children's. A membrane is the basis of membrane tissue, presented in the form of a thin polymer film and having such characteristics as water resistance and vapor permeability. For the production of this material, this film is coated with outer and inner protective layers. Their structure is determined by the membrane itself. This is done in order to preserve all useful properties even in case of damage. In other words, membrane clothing does not get wet when exposed to precipitation in the form of snow or rain, but at the same time it perfectly passes vapor from the body into the external environment. This throughput allows the skin to breathe.

Given all of the above, we can conclude that perfect winter clothing is made from such a fabric. The membrane, which is the basis of tissue, can be:

• with pores;
• without pores;
• combined.

Membranes with many micropores include Teflon. The size of such pores does not even reach the size of a drop of water, but is larger than a water molecule, which indicates waterproofness and the ability to remove sweat.

Membranes that do not have pores are typically made from polyurethane. Their inner layer concentrates in itself all the sweat secretions of the human body and pushes them out.

The structure of the combined membrane implies the presence of two layers: porous and smooth. This fabric has high quality characteristics and will last for many years.

Thanks to these advantages, clothes and shoes made of membrane fabrics and designed to be worn in the winter season are durable, but lightweight, excellent protection from frost, moisture, dust. They are simply indispensable for many active types of winter recreation, mountaineering.