The outer membrane is a relatively simple phospholipid bilayer, containing protein structures called porins[孔(道)蛋白] which render it permeable to molecules of about 10 kilodaltons or less(the size of the smallest proteins). lons, nutrient molecules, ATP, ADP, etc can pass through the outer membrane with easeThe outer membrane is a relatively simple phospholipid bilayer, containing protein structures called porins[孔(道)蛋白] which render it permeable to molecules of about 10 kilodaltons or less (the size of the smallest proteins). Ions, nutrient molecules, ATP, ADP, etc. can pass through the outer membrane with ease