Membraanlipiden

Three types of lipids are present in the membrane – phosphoglycerides, sphingolipids, and sterols.

Phosphoglycerides, also known as glycerophospholipids, contain a glycerol backbone with a hydrophilic phosphate group and two hydrophobic fatty acyl chains, usually 16 to 22 carbon atoms long.

Some of the most common phosphoglycerides present in the cell membrane are phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol - formed by the attachment of choline, ethanolamine, serine, and inositol, to the phosphate group.

Sphingolipids are lipids that contain a sphingosine backbone. Sphingosine is an amino alcohol with a long, unsaturated hydrocarbon chain. 

The simplest sphingolipid is ceramide, formed when a fatty acid molecule attaches to the amino group of the sphingosine.

The remaining hydroxyl group of ceramide can form esters with other chemical groups such as phosphocholine or carbohydrates, forming sphingomyelin or glycolipids, respectively.

The third type of membrane lipids, sterols, such as cholesterol, cannot independently form a lipid bilayer. They instead intercalate within phospholipid bilayers and act as a fluidity buffer for the membrane.