How does the plasma membrane controls what goes into and comes out of a cell?

Answer 1

The plasma membrane uses selective permeability, by which a membrane allows some substances into the cells while keeping others out. Picture a butterfly net, the holes in the allow knats and other bugs to pass through, while capturing others.

Answer 2

The plasma membrane is selectively permeable, meaning it regulates the passage of substances in and out of the cell. This is achieved through various mechanisms such as protein channels and transporters that allow specific molecules to enter or exit the cell. The lipid bilayer structure of the membrane also plays a role in controlling the movement of certain substances.