<Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> The diffusion of water through a selectively permeable membrane is called osmosis. This allows only certain particles to go through including water and leaving behind the solutes including salt and other contaminants . In the process of reverse osmosis, thin film composite membranes (TFC or TFM) are used . These are semipermeable membranes manufactured principally for use in water purification or desalination systems . They also have use in chemical applications such as batteries and fuel cells . In essence, a TFC material is a molecular sieve constructed in the form of a film from two or more layered materials . Prof. Sidney Loeb and Srinivasa Sourirajan invented the first practical synthetic semi-permeable membrane . Membranes used in reverse osmosis are, in general, made out of polyamide, chosen primarily for its permeability to water and relative impermeability to various dissolved impurities including salt ions and other small molecules that cannot be filtered . Another example of a semipermeable membrane is dialysis tubing . </P> <P> The semipermeable membrane is pertinent to cellular communication . A cell membrane consists of proteins and phospholipids . Signaling molecules send chemical messages to the proteins in the cell membrane . The signaling molecules bind to proteins, which alters the protein . A message is sent into the cell and a specific cellular response is turned on or activated . </P> <P> Other types of semipermeable membranes are cation exchange membrane (CEM), charge mosaic membrane (CMM), bipolar membrane (BPM), anion exchange membrane (AEM) alkali anion exchange membrane (AAEM) and proton exchange membrane (PEM). </P>

Two solutions are separated by a semipermeable membrane with the same properties as a cell membrane