All cells contain cell membranes. which of the following describes the composition of cell membranes?
a. cell membranes are composed of carbohydrate chains, which allow all materials to enter and leave the cell.
b. cell membranes are composed of cellulose, which provides rigidity for the cell.
c. cell membranes are composed of cytoplasm, which allows proteins to be excreted by the cell.
d. cell membranes are composed of lipid molecules, which provide a flexible structure.