The plasma membrane not only provides a protective boundary for the cell but also determines which substances enter or exit the cell. We call this characteristic:

Answer: selective permeability.

The cell is said to be selectively permeable

Explanation:the cell membrane is the membrane that covers the living portion of the cell. the is the boundary between the cell and it's extracellular environment.

The cell membrane contains lipids, proteins and carbonhydrate. the lipids forms a bilayer in which proteins are embedded. the bilayer allows some materials to move through the cell membrane more easily than others. thus the cell is said to be selectively permeable.

Small molecules such as oxygen gas, nitrogen gas, which can dissolve in the lipids, can easily pass through. uncharged molecules can also pass through eg carbon dioxide.

Large polar molecules eg glucose, amino acids etc. can not easily pass through and they may need to be carried by transport proteins