A key component of the cellular membrane in animals comprising phosph-lipids. The central compoent of a viral membrane, but not to be confused with the membrane/envelope protein in viruses, which is a protein anchored into the lipid bilayer

The lipid bilayer is central to animal membranes comprising phospho-lipids forming a dynamic structure into which transmembrane, membrane proteins and protein membrane channels are located. In viruses it is the singular component of the membrane/envelope and again not to be confused with either the membrane or envelope proteins. The viral membrane/envelope is formed from the host phospho-lipid membrane. Not all viruses contain an envelope.