Main Page | See live article | Alphabetical index A phospholipid is a lipid; this is the primary component of animal cell membranes. Phospholipids consist of a water-soluble head (a positively charged (polar) group), linked to two water-insoluble nonpolar tails (by a negatively charged phosphate group). Both tails consist of a fatty acid, each 14-24 carbon groups long. Due to its polar nature, the head of a phospholipid is attracted to water (it is hydrophilic). The nonpolar head is not attracted to water and is said to be hydrophobic. When placed in water, phospholipids form a bilayer, where the hydrophobic tails line up against each other. This forms a membrane with hydrophillic heads on both sides. This membrane is partially permeable and very flexible. See also: biochemistry, lipid, lipid bilayer This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.