Plasma membrane: the hidden border

The activity of the cell is possible only because different enzymes and substances do not mix, and the cell is integrity. All this becomes possible only through a variety of membranes. And the cell as a whole is demarcated from the other by a special structure called “cytoplasmic membrane”.

If you can See it in the light microscope? The answer is negative, Yes, we see the border, but the membrane itself – too thin structure. Sometimes we do not see even the borders of the cells, for example, when considered in the light microscope the liver cells. But why then do we in other cases, see boundaries of cells membranes which is it?

This is actually the atmosphere the layers of carbohydrates between cells. They absorb the dye, so if successful, the context you might think that this is the plasma membrane.

In experiments it was found that cells which were immersed in solutions with different osmotic pressure, swell or shrink, which means they are surrounded by a membrane, which is characterized by selective permeability.

It was Also revealed that the cell membrane is well drained if it is trying to penetrate substances that are soluble in lipids. In the classic concept gidrofilnye the ends of the molecules of the membrane was considered to be facing outside and hydrophobic inside. Electron microscopy proved that it is much more difficult. In particular, the photo shows that become dense outer layers and not the inner, that is, the lipid layers are located at the edges.

Plasma membrane due to their device impermeable to macromolecules, therefore, proteins of the cytoplasm is not able to leave the cell through it. Proteins while in the cell, creating an osmotic pressure, so that the right amount of water gets inside the cell. However, this process is not infinite, because the tissue fluid outside there is also other substances that balance the osmotic pressure.

To the potential difference remained stable plasmatic membrane must have dielectric properties. It also induces scientists to believe that in many membrane lipids, which have dielectric properties. Reluctantly disclose their properties plasma membrane.

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The Structure and functions of its related, for example, the ability to maintain an unusual concentration difference of potassium and sodium ions associated with a particular mechanism in the membrane-the sodium-potassium pump. The ionic transport has a special enzyme that works on energy cells, this process is costly for her. The cage had “pay” for balance. Also require a “attachments” and the uptake of glucose, fatty acids, amino acids.

An Interesting property of cell membranes is asymmetric, that is, the inner and outer surface uneven, although initially the researchers on the basis of electron microscopy data, thought so. All uglevodosoderzhaschie part glycoproteinic molecules protrude beyond the outer surface of the membrane and are involved in the formation Antipenko layer. The outer surface of the cell also contains special molecules called receptors, they react with certain molecules in the external environment. So regulate the activity of the cell, it is possible to stimulate or inhibit depending on the needs of the body. And in the inner half of the membrane contains a lot of cholesterol.

Biochemical studies of the cell membrane proved that the proteins of the inner and outer membranes are not identical, and different phospholipids in the composition of these two surfaces is also very diverse. Some of these features can be seen even with an electron microscope.

As you can see, the basic membrane is not so simple, but to understand the process, scientists had to build and discard many hypotheses.