What is unit membrane structure
The unit membrane of a cell is a continuous structure having one surface bordered by cytoplasm and the other by the outside world. It appears in thin sections with the electron microscope as a triple-layered structure about 7.5–10 nanometers thick consisting of two parallel dense strata each about 2.5 nm thick separated by a light interzone of about the same thickness.
The unit membrane concept that says that all membranes have an underlying bilayer composed of phospholipids