wat does cell membrane do?

Answer 1

The cell membrane has many,many specific functions. They can be summarize this way:
the cell membrane membrane forms a barrier between the inside of the c ell and the outside.
So that the chemical environments on the two sides can be different. The cell controls those differences so as to optimize the workings of the chemical machinery inside the cytoplasm. The cell also can cause brief changes in the internal by moving stuff across the membrane in a controlled way. These changes are the ways in which the cell membrane responds to events in the outside world.

Answer 2

Cell membranes allow things to pass into and out of the cell.