Final answer:
Phospholipid molecules, essential for cell membrane structure, have hydrophobic tails that turn inward to form a bilayer, with hydrophilic heads facing the watery environments inside and outside the cell.
Step-by-step explanation:
Phospholipid molecules are a major component of the cell membranes. Each phospholipid has distinct regions: a hydrophilic "head" and two hydrophobic "tails." The heads contain a phosphate group, which is attracted to water, hence their affinity for the watery solutions inside and outside the cell. Conversely, the tails, which consist of fatty acid chains, are repelled by water and therefore turn inward, away from the aqueous environment.
In an aqueous solution or cellular environment, phospholipids spontaneously arrange themselves into a bilayer. In this arrangement, the hydrophilic heads face outward towards the water, while the hydrophobic tails orient themselves inward, away from the water. This formation is crucial for forming the cell membrane's structure, providing a barrier that is selectively permeable to substances entering and exiting the cell.
Phospholipids' unique amphipathic nature—containing both water-loving and water-fearing parts—allows them to form the intricate matrix of the cell membrane. This structure is not just critical for protecting the cell but also for cell communication, transport of molecules, and various other functions essential for life.