Fatty acid chains 

Mainly two fatty acid chains of glycerophospholipids and the single fatty acid chain and the hydrocarbon chain of the sphingosine in sphingolipids consist of long chains of carbon atoms.  Commonly these chains have an even number of carbon atoms Example for palmitate, C16; stearate, C18 and are unbranched.  The chains  can either be completely saturated  with hydrogen  atoms or unsaturated  and have one or more  double  bonds  that are generally  in the cis con?guration instance Oleate C18:1 which has 18 carbon atoms and one double bond; arachidonic  acid C20:4 which has 20 carbon atoms and four double bonds. Two fatty acid chains on a glycerophospholipid are generally not identical for instance 1- stearoyl-2-oleoyl-3-phosphatidylcholine.

Figure: Structure of 1-stearoyl-2-oleoyl-3-phosphatidylcholine showing the saturated stearoyl (C18:0) and the mono-unsaturated oleoyl (C18:1) hydrocarbon chains. The hydrogen atoms surrounding the C=C bond are in the cis con?guration.