Cholesterol (a sterol) and Phosphatidylcholine (a glycerophospholipid) are two examples of amphipathic lipids. Looking at cholesterol you can see the four rings that are characteristic of a steroid and the aliphatic chain extending from the five membered D ring. The two methyl groups which are attached to the bridge carbons project toward you. Notice that since the rings are not aromatic they are not planar. The structural feature, that makes cholesterol not only a steroid but also a sterol, is the hydroxyl group on ring A. An amphipathic substance is one that is polar at one end of the molecule (hydrophilic) and nonpolar (hydrophobic) at the other. It is the oxygen of the hydroxyl that makes the A ring end of the molecule slightly polar, and the remainder of the molecule is hydrocarbon and therefore nonpolar. With only one oxygen atom cholesterol is not stronly amphipathic, but it is amphipathic enough to be a component of lipid bilayers.

Phosphatidylcholine, as with all glycerophospholipids, contains a diacylglycerol, a phosphate, and a nitrogen containing component which in this case is choline. The two acyl groups can easily be identified by looking for the two hydrocarbon chains that are somewhat twisted around each other. These two chains are attached to a glycerol,the three carbon segment with three oxygens, by carboxylic esters. The third oxygen of glycerol is connected to the phosphate (orange) which being being present as a diester is also bonded to the choline which is a two carbon unit containing a nitrogen (blue) bonded to three methyl groups. The nitrogen with its four bonds has a permanent positive charge, and the phosphate is negative since at physiological pH its third acidic hydrogen is ionized. This phosphate/choline end of the molecule being charged is polar (hydrophilic), but the opposite end consisting of hydrocarbon chains is nonpolar (hydrophobic).