Selectively permeable barriers Hydrated of living organisms: all solute membranes- intracellular and pl dasma Simple diffusion--virtuall Simple diffusion without transport impermeable to polar and charged species (too slow to be Diffusion meaningful); permeable for with transporter usIon certain gases- molecular oxygen, nitrogen, methane and △ Transport water(huge concentration) Passive transport(facilitated diffusion)-passage of polar compounds and ions aided by membrane proteins that lowers Transporter the activation energy Transporter or permeasesSelectively permeable barriers of living organisms: all membranes—intracellular and plasma Simple diffusion—virtually impermeable to polar and charged species (too slow to be meaningful); permeable for certain gases- molecular oxygen, nitrogen, methane and water (huge concentration) Passive transport (facilitated diffusion)—passage of polar compounds and ions aided by membrane proteins that lowers the activation energy Transporter or permeases