Plasma Membrane. Lipid bilayer. (A) A flat membrane of lipids assembled into bilayer. (B) Chemical structure of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, a common phospholipid with p ~1 and which thereby forms flat bilayers. A schematic lipid molecule is depicted in (C), with the hydrophilic headgroup represented in red and the double hydrophobic alkyl chain in grey. The molecule fits to a cylinder making its packing parameter p close to 1. (D) Lamellar phase Lα of fluid lipid bilayers. Not altered. CC. The multiple faces of self-assembled lipidic systems. Tresset G