Where exactly is the plasma membrane located

Biomembrane: overview and lipids

In biology, the cell is examined very closely more than once. Whether under the microscope or in connection with diffusion or other biological processes, the cell will always be with you. Here we would like to explain and show you the structure of the cell as it appears under the electron microscope.


The cell consists of an outer and an inner cell membrane. This is selectively permeable, which means that not all substances can pass through the membrane, only those that meet certain criteria. Depending on their polarity, size and charge, certain substances cannot pass at all or only to a limited extent or at different speeds without assistance.

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The biomembrane

The biomembrane consists of one Lipid bilayer. This means that not a single layer delimits the membrane, but rather two rows of lipids represent the delimitation of the cell. This is due to the fact that the membrane is important Transport functions must meet.
The membrane delimits the cell from the outside. It is extremely thin, almost too thin. The consistency can be compared to olive oil. The bare minimums are held, but rougher interventions destroy the membrane. This lipid layer, which we will go into in more detail later, is constantly in motion. She is particularly sensitive to stimuli.
In 1935, the biologists Dawson and Danielli hypothesized that the biomembrane consists of a lipid bilayer. Proteins are embedded in this membrane at the top and bottom. With this hypothesis, the two biologists defined the structure of the biomembrane for a longer period of time; the model went into literature as the Davson-Danielli model and lasted 37 years. Although it correctly explained the organization of the lipid molecules, it was unable to interpret the numerous properties of the membrane proteins without contradiction.

In 1972 it was replaced by the Fluid Mosaic model. This model describes the membrane as a liquid mosaic; it provides that the lipids form a viscous two-dimensional solvent into which proteins are embedded more or less deeply and in which they are anchored. This model, too, is now largely considered to be out of date, since practically all basic assumptions are not given in reality: Membrane proteins are present in such a high concentration that they do not swim 'far apart' in the lipid layer, but rather influence each other. In addition, most transmembrane proteins are much larger than the typical thickness of an undisturbed lipid bilayer.

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Lipids

A lipid is a particle that consists of - at least largely - water-insoluble substances. Lipids are also often called Fats referred to, but this is only a subgroup of lipids.

Lipids are the most important components of the biomembrane. They consist of a head and a tail. These differ in that the head is water-loving, but the tail is not. In biological terms, these two states are called hydrophilic (water-loving) and hydrophobic (not water-loving). The hydrophilic area shows to the outside.
Hydrophilic = water-loving
Hydrophobic = not water-loving

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