Prevent the passage of certain molecules into the cell.
Explanation:
Cell membrane or plasma membrane consists of lipid bilayer in which proteins are embedded. The carbohydrates are present in the plasma membrane in association with lipids and proteins.
The cell membrane acts as the semi-permeable membrane that allows the movement of selected particles into and out of the cell. The molecules may enter through diffusion, osmosis or by active transport depending on the tyep of molecule.