What is the structure of a phospholipid bilayer?

The structure of a phospholipid bilayer is accurately described by the idea that it consists of a double layer of phospholipids with their heads facing outward. This arrangement is crucial for the formation of cell membranes. In a phospholipid, there is a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails.

The phospholipids align themselves in such a way that the hydrophilic heads are oriented toward the aqueous environment inside and outside of the cell, while the hydrophobic tails face each other in the interior of the bilayer, shielded from the water. This orientation contributes to the membrane's fluidity and the selective permeability of the cell, allowing certain substances to enter and exit while forming a barrier against others.

This bilayer structure is fundamental to cell biology and underlies various cellular functions, such as signaling and transport processes. Understanding this arrangement helps in grasping more complex concepts related to membranes and their functions in living organisms.