Fig. 1. Diagrammatic representation of a biological membrane bilayer (A), with the molecular structure of two representative phospholipids: a polyunsaturated phosphatidylcholine (B) and a monounsaturated phosphatidylcholine (C). In both structures, neither C nor H are shown, although the carbon atoms are numbered in the right-hand chain in C. (D) Three representative conformations of docosahexaenoic acid (DHA) (22:6) acyl chain (solid line) in a phosphatidylcholine molecule (these conformations are from fig. 12 of Feller et al., 2002). In D, the sn-1 acyl chain is shown as a broken line.