Final answer:
The most common lipids found in most cell membranes are phospholipids, which have a hydrophilic head and hydrophobic tails and organize into a lipid bilayer structure.
Step-by-step explanation:
The most common lipids in most cell membranes are the phospholipids. Phospholipids consist of a hydrophilic head made up of a phosphate group and glycerol, and two hydrophobic fatty acid tails. This amphipathic nature of phospholipids allows them to form a lipid bilayer, which is essential for cell membrane structure and function. Phospholipids are the main fabric of the membrane, with their hydrophilic heads facing the aqueous environment inside and outside the cell, and their hydrophobic tails facing each other, forming the membrane's interior.