Double lipid layer
A lipid bilayer (or lipid bilayer ) is a structure that many amphiphilic lipids form when mixed with a polar solvent (e.g., water ). When mixed with an apolar solvent (e.g. oil ) an inverse double lipid layer forms .
A double lipid layer consists of amphiphilic lipids, which have a hydrophilic and a hydrophobic part (mostly hydrocarbon chains ). A double layer forms in the polar solvent, with the hydrophobic part facing inwards and the hydrophilic part facing outwards. In the non-polar solvent, the situation is reversed accordingly (so-called inverse double lipid layer).
A double lipid layer is almost impermeable to polar molecules or macromolecules, but at the same time very flexible and mechanically difficult to destroy. For this reason, even a puncture with a pipette does not leave a hole in the membrane. Likewise, water and small, uncharged molecules can diffuse through the double lipid layer without damaging them. The double lipid layer can be destroyed by lipid solvents and lipases.
Double lipid layers can exist in different phases , which differ mainly in the mobility of the lipids in the plane of the layer. In the gel-like or liquid-crystalline phase, the lipid tails are arranged close to one another, while in the liquid or fluid phase, like in a liquid, they are disordered and very mobile. In this phase, the double lipid layer is also described as a two-dimensional liquid .
In 1925, Evert Gorter and François Grendel first described a double lipid layer as the main component of biological membranes (such as the cell membrane ). It serves as a separating layer between cell compartments or the inside and outside of the cell. The double lipid layer of a biological membrane consists essentially of phospholipids , which are normally in the liquid phase so that the other components of the membrane remain mobile.
Individual evidence
- ^ E. Gorter, F. Grendel: On bimolecular layers of lipids on the chromocytes of the blood. In: The Journal of experimental medicine. Volume 41, Number 4, March 1925, pp. 439-443, PMID 19868999 , PMC 2130960 (free full text).