Final answer:
The lipid bilayer is a selectively permeable barrier that controls the movement of molecules in and out of the cell.
Step-by-step explanation:
The lipid bilayer is a crucial component of cell membranes and is responsible for controlling the movement of molecules in and out of the cell.
The lipid bilayer is formed by two layers of phospholipids, with the hydrophilic (water-loving) heads facing outward and the hydrophobic (water-fearing) tails facing inward.
This arrangement creates a selectively permeable barrier that allows some substances, such as small hydrophobic molecules, to pass freely, while regulating the movement of larger molecules and charged particles through the use of transport proteins and channels.
Learn more about Cell membrane structure and function