What is one difference between a cell wall and a cell membrane? (a) cell walls have gap junctions. cell membranes have plasmodesmata. (b) cell walls act as a boundary that nothing can pass through. cell membranes allow materials in and out of the cell (c) cell walls are found inside the cell membrane. the cell membrane is the outermost structure of a cell (d) cell walls are made of cellulose. cell membranes are made of proteins and phospholipids