Are a major component of cell membranes. they form a bilayer with their hydrophobic tails mingling together and their hydrophilic heads facing the watery environment on both sides of the membrane.

The answer is phospholipids. The phospholipids are a group of lipids that are main constituent of all cell membranes in which they can make lipid bilayers because of their amphiphilic feature. The arrangement of the phospholipids molecule primarily includes of two hydrophobic fatty acid tails and hydrophilic head consisting of phosphate group. The two constituents are linked by a glycerol molecule and phosphate class can be altered with organic molecules such as choline.