The primary structural feature of a phospholipid is its amphiphilic nature, consisting of a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." This dual nature allows phospholipids to form bilayers, which are fundamental components of cell membranes. The hydrophilic heads face outward toward the aqueous environment, while the hydrophobic tails align inward away from water, creating a selective barrier. This arrangement is crucial for maintaining the integrity of cells, facilitating membrane fluidity, and enabling the formation of compartments within cells, thus supporting various biological functions.