The fundamental structure of the lipid barrier is the phospholipid bilayer. Each phospholipid molecule has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. These molecules arrange themselves into a bilayer, with the hydrophobic tails facing inward and the hydrophilic heads facing outward, creating a semi-permeable membrane. Cholesterol molecules are interspersed within the bilayer, providing stability and fluidity. Additionally, various proteins are embedded within this lipid matrix, serving as channels, receptors, and enzymes.
