Lipid bi-layer

The lipid bi-layer provides a basic impermeable barrier around cells, and is approximately 5nm thick. They help to maintain different environments between cytosol and the extracellular environment/organelles, and also control the transport of solutes between compartmentsThe lipid bilayer consists of four major phospholipids which are; phopshatidylethanolamine, phosphatidylserine, phosphatidycholine and sphingomyelin. These are derived from glycerol apart from sphingomyelin, which is derived form serine. Phosphatidylserine is the only one negatively charged.