How is the structure of the cell membrane adapted to its function of selective permeability?

Because lipid bilayers, which make up cell membranes, are fluid in nature—that is, they move continuously and are selectively permeable to compounds—and because too much fluidity in the membrane can damage the plasma membrane,'sterols,' or cholesterol, are linked to the membranes to control their fluidity.

The composition and arrangement of the cell membrane are intricately tailored to its function of selective permeability, allowing it to effectively control the flow of substances into and out of the cell. This is mainly accomplished by the following features: 1. Phospholipid Bilayer: Phospholipids are arranged in two layers, with their hydrophilic (water-attracting) heads facing outward towards the water inside and outside the cell, and their hydrophobic (water-repelling) tails facing inward, away from the water. This arrangement creates a hydrophobic barrier that prohibits the free passage of water-soluble substances.2. Protein Channels and Carriers: Phospholipids are incorporated into the cell membrane.