Answer:
The answer is: phospholipid molecules
Step-by-step explanation:
The plasma membrane of a cell is consists of a lipid bilayer. This lipid bilayer, also known as the phospholipid bilayer, is a polar membrane composed of two layers of lipid molecules, usually amphipathic phospholipid molecules.
The amphipathic phospholipid molecules have a hydrophilic phosphate head on the exterior and a hydrophobic tail consisting of fatty acid chain on the interior of the membrane.