Phospholipids in the context of "Lecithin"

In chemistry, an amphiphile (from Greek αμφις (amphis) 'both' and φιλíα (philia) 'love, friendship'), or amphipath, is a chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving, nonpolar) properties. Such a compound is called amphiphilic or amphipathic. Amphiphilic compounds include surfactants and detergents. The phospholipid amphiphiles are the major structural component of cell membranes.

Amphiphiles are the basis for a number of areas of research in chemistry and biochemistry, notably that of lipid polymorphism.

A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine.

Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids, di- and monoglycerides. These then pass from the intestinal lumen into the enterocyte, where they are re-esterified to form triglyceride. The triglyceride is then combined with phospholipids, cholesterol ester, and apolipoprotein B48 to form chylomicrons. These chylomicrons then pass into the lacteals, forming a milky substance known as chyle. Lacteals regulate chylomicron uptake through specialized button-like endothelial junctions that facilitate entry of dietary lipids into the lymphatic lumen.The lacteals merge to form larger lymphatic vessels that transport the chyle to the thoracic duct where it is emptied into the bloodstream at the subclavian vein.

Lamellar phase refers generally to packing of polar-headed, long chain, nonpolar-tailed molecules (amphiphiles) in an environment of bulk polar liquid, as sheets of bilayers separated by bulk liquid. In biophysics, polar lipids (mostly, phospholipids, and rarely, glycolipids) pack as a liquid crystalline bilayer, with hydrophobic fatty acyl long chains directed inwardly and polar headgroups of lipids aligned on the outside in contact with water, as a 2-dimensional flat sheet surface. Under transmission electron microscopy (TEM), after staining with polar headgroup reactive chemical osmium tetroxide, lamellar lipid phase appears as two thin parallel dark staining lines/sheets, constituted by aligned polar headgroups of lipids. 'Sandwiched' between these two parallel lines, there exists one thicker line/sheet of non-staining closely packed layer of long lipid fatty acyl chains. This TEM-appearance became famous as Robertson's unit membrane - the basis of all biological membranes, and structure of lipid bilayer in unilamellar liposomes. In multilamellar liposomes, many such lipid bilayer sheets are layered concentrically with water layers in between.

In lamellar lipid bilayers, polar headgroups of lipids align together at the interface of water and hydrophobic fatty-acid acyl chains align parallel to one another 'hiding away' from water. The lipid head groups are somewhat more 'tightly' packed than relatively 'fluid' hydrocarbon fatty acyl long chains. The lamellar lipid bilayer organization, thus reveals a 'flexibility gradient' of increasing freedom of motions from near the head-groups towards the terminal fatty-acyl chain methyl groups. Existence of such a dynamic organization of lamellar phase in liposomes as well as biological membranes can be confirmed by spin label electron paramagnetic resonance and high resolution nuclear magnetic resonance spectroscopy studies of biological membranes and liposomes.