What is the plasma (cell) membrane? What is its main function?

The plasma membrane, also called the cell membrane, is the membrane found in all cells that separates the interior of the cell from the outside environment.

The plasma membrane, or the cell membrane, provides protection for a cell. It also provides a fixed environment inside the cell. And that membrane has several different functions. One is to transport nutrients into the cell and also to transport toxic substances out of the cell.