A ceramide is a type of sphingolipid resulting from the combination of a fatty acid with sphingosine via an amide bond. Such molecules are abundant in cell membranes, where they are involved in the composition of sphingomyelins. Ceramides play not only a structural role in biological membranes but can also serve as lipid signaling molecules. Their well-understood actions range from cellular differentiation to programmed cell death (apoptosis) to cell proliferation.
Most ceramides do not exist naturally as such but rather as precursors in the biosynthesis of sphingolipids through an addition reaction on the primary alcohol function of sphingosine.
