Cell membranes (plasma membranes) organisms maintain homeostasis by controlling what substances may enter or leave cells. some substances can cross a cell membrane through passive transport, while other substances can only cross a cell membrane through active transport. what is the difference between active and passive cellular transport? a. active transport requires the cell to expend energy, while passive transport does not. b. passive transport is the only form of transport that requires the use of protein carriers. c. active transport is the only form of transport that requires the use of protein carriers. d. active transport requires the cell to form vesicles, while passive transport is done through osmosis.