The plasmatic membrane, Cell membrane or cytoplasmic membrane, is a biological membrane that separates the interior of all cells from the external environment.
Each cell of the organism is encapsulated in a small membrane bubble, consistent and permeable with the medium.
All animal cells, plant cells, prokaryotic cells and fungal cells have a plasma membrane. The inner organelles of each cell are also encapsulated in cell membranes.
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15 Characteristics of the cell membrane
1- Pervious texture
The cell membrane has a texture similar to salad oil, that is, it is permeable to its environment and allows it to interact with what happens outside in a controlled way. This property also allows you to excrete certain items as well as absorb what you need.
This texture also allows them to communicate with other cells, identify themselves and share information.
2- Fluid mosaic model
This is the currently accepted model for cell membrane structure. It was proposed in 1972 and indicates that this membrane is a mosaic of components, primarily phospholipids, cholesterol and proteins, that move freely and fluidly in the plane of this mosaic.
The cell would always be in a dynamic process, where phospholipids and proteins are continually slipping alongside each other. Its fluidity is so great that if it is punctured with a needle, the membrane flows around it. Upon withdrawal, the membrane will return to its normal flow.
3- Its main components are lipids
The main components of the cell membrane are lipids in the form of cholesterol and phospholipids. In addition, it contains proteins and carbohydrates attached to these lipids and proteins.
Phospholipids are lipids composed of glycerol. Cell membranes usually involve two layers of phospholipids in a system called phospholipid bilayer.
Cholesterol is another lipid composed of 4 coals, which is found next to the phospholipids in the nucleus of this cell membrane. Carbohydrates are present on the surface of the plasma membrane and are linked to the proteins, forming glycoproteins.
4- It allows to form the cell
Despite its permeability, the cell membrane has sufficient consistency to shape the cells. It is the base where the cytoskeleton attaches in some organisms and the cell walls in others. It is the support of the cell.
5- Regulates cell growth
The cell membrane regulates the growth of cells through the balance between the processes of endocytosis and exocytosis. In endocytosis, lipids and proteins are removed from the cell membrane and incorporated into the cell.
On the other hand, during exocytosis, vesicles containing lipids and proteins fuse with the cell membrane and increase in size.
6- It allows the communication between the cells
It has proteins called surface marker proteins that allow the cell to be identified and allow it to communicate with other nearby cells.
The cell membrane has reception sites for the interaction of specific biochemical elements such as certain hormones, neurotransmitters and proteins of the immune system. In this way, the cell can recognize and process some signals received by the extracellular environment.
7- Metabolic activity
Another feature of the cell membrane is that it includes in its structures some proteins and related enzymes in some of the metabolic processes of the cell.
8- It is part of the structure of the cell
The cell membrane is part of the structure of cells and not a cell itself. However, because of its characteristics, it can perform so many functions that it is probably the most complete cellular structure, for its ability to perform specific tasks in multiple levels of detail.
9- Is involved in the process of transporting the cell
The cell membrane is responsible for selecting which elements can enter the cell. These can be amino acids, nucleotides and sugars.
This is why the cell membrane has certain specific structures that allow certain molecules such as those mentioned to be translated. There are two types of transport process in the cell:
Passive transport involves diffusion-related non-polar molecules; And also osmosis - which is related to water molecules. In neither of these two processes does the cell expend energy.
Active transport is when a molecule must be propelled by the cell through its membrane, occupying osmosis, diffusion or polarity, against the natural direction. This process does require energy.
10- It can form other membranes
The cell membrane may form other types of"supermembranes"and different types of cell junctions. These are composed of specific proteins, such as integrins and cadherins, all cell adhesion molecules. Some of these"supermembranes"are caveolas, among others.
11- Its density is variable from cell to cell
Depending on the type of cell, the density of the cell membrane may vary. This is according to the function that each cell must perform and its independent requirements. The axons and their covers, the axolemas, have different density in their cellular membrane.
12- It is composed of 50% of proteins
The cell membrane is approximately 25% to 75% protein. These are located in the middle of the two lipid bilayers that form the membrane. Phospholipids are the basic structure, while proteins perform the specific functions of the different tasks of the cell.
13- It has cholesterol
The cell membrane has cholesterol in its coating, this allows it to maintain its fluidity and permeability, which keeps the inside of the cell in a contact protected with its environment.
14- Contains glycoproteins on the outside
Glycoproteins present in the cell membrane are used for recognition between cells, in addition to acting as antigens and receptors.
15- Act as a border
The cell membrane allows living cells to be separated from other wastes excreted by the body, including damaged or dead cells. This protects the integrity of healthy cells in the body.
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