Lipidikuoret

Lipidikuoret, often translated as lipid envelopes or lipid bilayers, are fundamental structures in biology. They are composed of a double layer of lipid molecules, primarily phospholipids. Each phospholipid molecule has a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. In an aqueous environment, these molecules spontaneously arrange themselves into a bilayer with the hydrophilic heads facing outwards, interacting with the surrounding water, and the hydrophobic tails facing inwards, away from the water. This arrangement creates a stable barrier that separates the interior of a cell from its external environment, or separates different organelles within a cell.

The lipid bilayer is not a rigid structure. It is fluid, allowing individual lipid molecules to move laterally and rotate. This fluidity is influenced by factors such as temperature and the types of fatty acids in the lipid tails. Unsaturated fatty acids, with their kinks, increase fluidity, while saturated fatty acids, which pack more tightly, decrease it. Embedded within and attached to the lipid bilayer are various proteins, which perform a wide range of functions. These proteins can act as channels or transporters for molecules, receptors for signals, enzymes, or structural components. The specific composition of lipids and proteins in the bilayer determines its unique properties and functions in different biological membranes.