GLOSSARY

Sphingomyelin is a phosphocholine-containing sphingolipid found in membranes and myelin, lacking the glycerol backbone of glycerophospholipids.

Sphingolipids use a sphingoid base, and the fatty acid in ceramide is amide-linked rather than arranged like an ordinary glyceride. Different heads produce phosphate-containing or sugar-containing members. Structural families can therefore overlap in head-group characteristics; membrane lipids should not all be assumed to be triglycerides or to have a glycerol backbone.

Many common phospholipids have a phosphate-containing head and fatty tails that organise in water. Not all have a glycerol backbone: sphingomyelin is an important exception. Phospholipid names describe a structural family, not every attached fatty acid, its dietary quantity or the quality and effectiveness of a supplement claiming to contain it.

Head groups distinguish phospholipids: choline, ethanolamine, serine and inositol are not interchangeable substances. A group bound within a molecule is not equivalent to consuming the free substance with identical effects. In particular, ethanolamine is not beverage alcohol, and a serine head does not imply the same action as a free amino-acid supplement.