Plasma membrane


The plasma membrane, also called the cell membrane , is a layer composed of proteins, phospholipids and glycolipids that covers and envelops cells, providing them with protection and keeping them separated from the environment. It is a protective barrier between the cell and the external part that surrounds it or the environment, this because it works as a mechanism for the entry and exit of molecules through it. With its selective permeabilitymanages to determine which substances must enter the cell for its proper functioning. To maintain and preserve life, there are a series of chemical reactions that are necessary to maintain it and the cell, for this reason, needs an internal environment that is appropriate to perform this function, and for this, there is the plasma membrane.


What is the plasma membrane?

The plasma membrane or cell membrane is a layer that has a selective permeability mechanism , which functions as a protective barrier for the cell with the external environment that surrounds it and thus allows the entry and exit of molecules to the interior. of the cell, helping to maintain a proper intracellular and extracellular balance.

  • Characteristics of the plasma membrane
  • Components (edit)
  • Structure of the plasma membrane
  • Function of the plasma membrane
  • Properties of the plasma membrane

Characteristics of the plasma membrane

The plasma membrane measures between 6 and 10 manometers, which means that it is very thin. It is made up of three layers, two internal lines and two external lines, and in between is a thinner layer called a fluid mosaic pattern . Its main characteristic is selective permeability , which allows the membrane to decide which molecules enter which must leave the cell. It is consistent, which allows you to shape cells while supporting them. Regulates cell growth by balancing endocytosis and exocytosis processes .


Components (edit)

Among the main components of the plasma membrane are lipids (which include phospholipids and cholesterol), proteins, and carbohydrates . The phospholipids form the basic structure of the plasma membrane. The second component of plasma membranes is proteins. There are two important categories of membrane proteins: integral and peripheral.. Integral proteins are within the membrane and peripheral proteins are located outside the cell and are bound to phospholipids. The third component is the carbohydrates located on the outer surface of the cell and together with proteins they form a mechanism to identify molecules, an important part of our immune system as they make a difference between the cells that should be attacked and those that should not.

Structure of the plasma membrane

Its structure is based on two sheets composed of glycolipids , phospholipids and proteins that surround the cell, give it shape and help it maintain an adequate balance between the intracellular and extracellular environment of the cell. Observed in an electron microscope you can see two dark bilateral layers and a lighter one located in the center.

Function of the plasma membrane

Its most important function is to keep the internal environment of the cell separated from the phospholipid layer, in addition to being a transport medium , being a selective barrier that allows the cell to differentiate itself from the environment that surrounds it. It allows the cell to divide into organelles and in this way it manages to protect the chemical reactions that occur in each of them. It forms a permeable barrier through which only substances that are really necessary enter or leave. It works as a means of transport carrying substances from one place to another within the membrane. It measures all the interactions that occur between internal and external cells. As the membrane is the cell boundary, the membrane works as a means of protection, being a barrier that differs between harmful substances and pathogenic organisms that enter the body. Likewise, the membrane is responsible for the relationship and communication of other cells, as it contains receptors (mainly proteins) that recognize signals from certain molecules and that are responsible for transmitting information to the cytoplasm so that it reaches the nucleus. Finally, the plasma membrane is responsible for shaping the cell through the components it has in the extracellular matrix.

Properties of the plasma membrane

It has an important property of selectivity , which allows it to expel waste resulting from metabolism from the cell, helps to incorporate nutrients and also exchanges ions necessary to maintain the functions of the cells such as muscle contraction, release of hormones and neurotransmitters . Another property of the membrane is its fluidity which depends on the unsaturated fatty acids found in the molecules, when these acids are fatty, the membrane will have greater fluidity. The plasma membrane is permeable to hydrophobic substances and is impermeable to ions or substances of increased size such as carbohydrates and amino acids, it is for this reason that we can say that it is alsosemi-permeable since it allows the preferential passage of some substances located outside it.

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