Answer:
Phospholipids
Step-by-step explanation:
Phospholipids are a particular kind of lipid (an oil) that forms a two-layered surface that surrounds and protects all living cells. The phosphates are essential to forming this bilayered structure. This membrane has a semipermeable function that selectively allows some elements and molecules to go in or out of the cell and thus helps maintain the cell in equilibrium.