l. Insert: phospholipid.gif (from Chris) and delete following gif

Legend: Three different Structural Representations of a Phospholipid: from left to right, a ribbon form, a stick or skeleton form, and the space-filling model. Note that the presence of one or more double bonds in the cis form produces "kinks" in the acyl tails, because carbons are unable to rotate around a double bond.

2. Legend: Three Different Structural Representations of Cholesterol: from left to right, the stick or skeleton form, the ribbon form, and the space-filling form. The heterocyclic backbone of cholesterol forms a planar structure, severally limits the flexibility of cholesterol and produces kinks in any aggregate of amphipathic molecules containing cholesterol.

3. Legend: The Stick Structures of Some Common Classes of Membrane Lipids. The stick structures are arranged to emphasize the molecules' amphipathic nature, with nonpolar groups projecting to the left and polar residues projecting towards the right. Abbreviations: Gal, galactose; Glc, glucose; NeuNAc, N-acetylneuraminic (sialic) acid; GlcNAc, N-acetylglucosamine.