In Figure 2 the phospholipid molecule is represented by the shaded oval with two tails and membrane proteins are represented by twisting lines carrying positive and negative charges. Figure 3, on the next page, is an illustration of a phospholipid molecule, which makes up the bulk of the cell membrane. In this illustration, phosphatidylcholine distearate is used as an example (there are several other similar molecules in cell membranes) and the polar, water-soluble head and non-polar, lipid-soluble tails of the molecule are indicated.