Biological membrane 4817 222271885 2008-06-28T13:01:14Z PhilKnight 1812441 ref {{see also|Membrane}} [[Image:Phospholipids aqueous solution structures.svg|thumb|200px|right|Cross section view of the structures that can be formed by phospholipids in aqueous solutions]] A '''biological membrane''' or '''biomembrane''' is an enclosing or separating [[amphipathic]] layer that acts as a barrier within or around a [[cell (biology)|cell]]. It is, almost invariably, a [[lipid bilayer]], composed of a double layer of [[lipid]]-class [[molecules]], specifically [[phospholipid]]s, with occasional [[integral membrane protein|proteins]] intertwined, some of which function as [[ion channel|channels]].<ref>{{citebook|title=Neurophysiological basis of movement|author=Mark L. Latash|year=2007|id=ISBN 0736063676}}</ref> ==Function== Such membranes typically define enclosed spaces or [[compartment]]s in which cells may maintain a [[chemistry|chemical]] or [[biochemistry|biochemical]] [[environment (biophysical)|environment]] that differs from the outside. For example, the membrane around [[peroxisome]]s shields the rest of the cell from [[peroxide]]s, and the [[plasma membrane]] separates a cell from its surrounding medium. Most [[organelle]]s are defined by such membranes, and are called '''membrane-bounded''' organelles. Probably the most important feature of a biomembrane is that it is a [[selective permeability|selectively-permeable]] structure. This means that the size, [[electric charge|charge]], and other [[chemical properties]] of the [[atoms]] and molecules attempting to cross it will determine whether they succeed to do so. Selective permeability is essential for effective separation of a cell or organelle from its surroundings. Biological membranes also have certain mechanical or [[Elasticity of cell membranes|elastic properties]]. If a particle is too large or otherwise unable to cross the membrane by itself, but is still needed by a cell, it could either go through one of the protein channels or be taken in by means of [[endocytosis]]. == Types of biological membranes == * [[Cell membrane]] * [[Mucous membrane]] * [[S-layer]] == See also == *[[Membrane lipids]] *[[Endomembrane system]] that divides the cell into organelles *[[Outer membrane]] or [[inner membrane]] of an organelle *[[Biofilm]] *[[Membrane protein]] *[[Osmosis]] ==References== {{refs}} ==External links== *{{MeshName|Membranes}} [[Category:Membrane biology| ]] [[Category:Biological matter|membrane]] [[cs:Membrána (buňka)]] [[de:Biomembran]] [[fr:Membrane (biologie)]] [[he:ממברנה ביולוגית]] [[lb:Biomembran]] [[ja:生体膜]] [[pl:Błona biologiczna]] [[ru:Биологические мембраны]]