membranous structures, called inclusions, which lie free in the cytosolic
extracellular face (EF) and protoplasmic face (PF) of each leaflet are
compartment. They include lipid droplets, glycogen aggregates and pig-
artificially produced during membrane splitting. This technique has
ments (e.g. lipofuscin). In addition, ribosomes and several filamentous
also demonstrated intramembranous particles embedded in the lipid
protein networks, known collectively as the cytoskeleton, are found in
bilayer; in most cases, these represent large transmembrane protein
the cytosol. The cytoskeleton determines general cell shape and sup-
molecules or complexes of proteins. Intramembranous particles are
ports specialized extensions of the cell surface (microvilli, cilia, flag-
distributed asymmetrically between the two half-layers, usually adher-
ella). It is involved in the assembly of specific structures (e.g. centrioles)
ing more to one half of the bilayer than to the other. In plasma mem-
and controls cargo transport in the cytoplasm. The cytosol contains
branes, the intracellular leaflet carries most particles, seen on its face