P ERMEABILITY OF MEMBRANES Permeable – substance is able to cross a membrane Impermeable – substance cannot pass across the membrane Selectively permeable – some substances can pass and some cannot pass

C ELL T RANSPORT Passive Transport – no energy Diffusion Facilitated diffusion Osmosis Active Transport – energy required Endocytosis Phagocystosis Exocytosis

P ASSIVE T RANSPORT Passive Transport Clip Summary: Diffusion – movement of ions from area of high concentration to an area of low concentration Facilitated – aided movement across the cell membrane using protein channels

P ASSIVE T RANSPORT ( CONTINUED ) Osmosis – facilitate diffusion of WATER using aquaporins (water channel proteins) Since the cell membrane (lipid bilayer) has a hydrophobic layer, it does not allow water molecule to pass through freely

A CTIVE T RANSPORT Introduction Active Transport Clips Endocytosis and Exocytosis Phagocytosis

A CTIVE T RANSPORT S UMMARY Movement of materials from an area of low concentration to an area of high concentration – requires energy Protein pumps – small molecules, use ATP, change shape, bind substance on one side and release on the other side of the membrane Endo cytosis – cell membrane creates a vesicle that contains the particle Exo cytosis- vesicle fuses with cell membrane and releases particle out of the cell