It is a feature and a function of the plasma membrane that allows selection of what and when particles enter and leave the cell

It is a feature and a function of the plasma membrane that allows selection of what and when particles enter and leave the cell.

This function is essential to maintain the homeostasis by regulating the passage of some substances while preventing others from entering the cell.

This selection is possible because the structure of the plasma membrane is composed of a phospholipid bilayer which blocks all polar and charged particles while allowing nonpolar molecules, and that act as transporters or channels for molecules that fit the protein's specific conformation.