Functions of the cell membrane
As the complex structure of cell membranes already suggests, they have many different functions to fulfil, which can vary greatly depending on the type and localisation of the cell. On the one hand, membranes generally represent a barrier. A function that should not be underestimated.
In our body, countless reactions take place in parallel at any given time. If they all took place in one and the same space, they would strongly influence and even cancel each other out.There would be no regulated course of the metabolism possible and the human being, as it exists and functions as a whole, would be unimaginable. Thus, they simultaneously serve as a transport medium for a wide variety of substances, which are transported across the membrane by means of transporters.
In order to be able to work together as an organ, the individual cells must be in contact via their membranes. This is achieved by different connecting proteins and receptors. Via the receptors, cells can identify each other, communicate and exchange information.
Glycocalyx, for example, serves as one of the many recognition features between endogenous and foreign cells. Receptors are proteins that receive signals from outside the cell and pass them on to the cell nucleus and thus to the cell’s “brain“. Depending on the chemical properties of the chemical particle that has docked to the receptor, it is located either on the outside of the cell, inside the cell or in the cell membrane.
But cells themselves can also be information carriers. Probably the best known of our body are the nerve cells. For them to be able to perform their function, their membranes must be able to conduct electrical signals.
Electrical signals are generated by different charges inside and outside the cells. This difference in charge, also called gradient, must be maintained. In this context, one also speaks of a membrane potential.
Cell membranes separate the differently charged areas from each other, but at the same time contain channels that allow a short-term reversal of the charge conditions so that the actual current and thus the information to be passed on can flow. This phenomenon is also called action potential. The cell membrane as such is impermeable for larger molecules and ions.
In order for an exchange to take place between the cell interior and the environment, the cell membrane contains proteins that transport various molecules into the cell and out of the cell. These proteins are divided into channels through which a substance passively enters or leaves the cell along the concentration difference. Other proteins must apply energy to actively transport substances through the cell membrane.
Another important form of transport is the vesicle. Vesicles are vesicles that are constricted from the cell membrane. Through these vesicles, substances produced in the cell can be released into the environment. In addition, substances from the cell’s environment can also be removed in this way.