Answer:
-Cellulose.
-Increased strength to the cell
Step-by-step explanation:
The cell membrane or plasma membrane is an outer covering of cells that separate interior of the cells from external environment.
It is made up of lipids and proteins. The main function of plasma membrane is to allow selective transport of substances to enter or exit from the cell.
Thus, cellulose and providing strength to the cells are characteristics of plasma membranes.