This statement is true. Cell membranes exhibit two principles called selective permeability and semi-permeability, often incorrectly used interchangeably! The first means that the composition of the cell membrane allows for some specific molecules to perfuse into and out of the cell while disallowing other specific molecules, depending on certain cellular conditions, properties, functions, and metabolic activity. If the cytoplasm is a party, the cell membrane is the security guard that checks the list and either bounces guests or lets them pass the stanchion. The second means that the membrane distinguishes which molecules can pass according to their size, electrical charge, solubility, and other properties (chemical or physical) that fit or do not fit the cell's needs.