Which is a function of the cell membrane?
a. performs photosynthesis
b. controls what enters and leaves the cell
c. protects the external structures of the cell
d. provides energy to the cell

B. Controls what enters and leaves the cell.

The cell membrane ( plasma membrane)  surrounds the cell and primarily made up of lipids and proteins. It controls what enters and leaves the cell that is why it is also called as a selectively permeable membrane. It does this by not allowing the useful substances to go out and the harmful substances to enter the cell. In this way, it provides protection to the cell.

Some of the essential cellular processes related to cell membrane are- Cell signaling, endocytosis, exocytosis, cell adhesion etc.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

not sure if this is what you'r looking for nnew= nold