Transport of molecules within a cell and out of the cell requires a complex endomembrane system. Endocytosis occurs when the cell membrane engulfs particles (dark blue) outside the cell ...

eg urea No Osmosis Water moves from a high to a low concentration across a partially permeable membrane and down a concentration gradient Water No Active transport Substances move against a ...

A plasma membrane is permeable to specific molecules that a cell needs. Transport proteins in the cell membrane allow for selective passage of specific molecules from the external environment.