Final answer:
The cell membrane functions as a barrier, controls the movement of substances, and plays a role in cell adhesion and signaling.
Step-by-step explanation:
The function of the cell membrane is to provide a barrier around the cell, separating its internal components from the extracellular environment. It controls the movement of substances in and out of the cells and organelles, regulates which materials can pass through, and plays a role in cell adhesion, signaling, and attachment of the cytoskeleton and extracellular matrix.