What is Cell membrane?
[[File:Cell membrane drawing-en.svg|thumb|300px|Cell membrane]] [[File:Cell_membrane_detailed_diagram_en.svg|thumb|right|300px|Make-up of a [[eukaryote]] cell membrane]] The '''cell membrane''' is a thin flexible layer around the [[cell]]s of all living things. It is sometimes called the '''plasma membrane''' or cytoplasmic membrane. Its basic job is to separate the inside of cells from the outside.<ref>[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellMembranes.html Kimball's biology pages] {{Webarchive|url=https://web.archive.org/web/20090125224255/http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellMembranes.html |date=2009-01-25 }}, Cell membranes</ref><ref>{{cite book |author=Singleton P|title=Bacteria in biology, biotechnology and medicine |edition=5th |isbn=0-471-98880-4 |year=1999 |publisher=Wiley |location=New York}}</ref> In all cells, the cell membrane separates the [[cytoplasm]] inside the cell from its surroundings. [[Animal]] cells are contained in just a membrane. [[Bacteria]], [[fungi]] and [[plant]]s have strong [[cell wall]]s as well, which support the cell and block the passage of large [[molecule]]s. == Structure == [[File:Phospholipid TvanBrussel.jpg|thumb|right|200px|The phospholipid bilayer]] The membrane is made up of a thin layer called the '[[lipid bilayer|phospholipid bilayer]]'. This has two layers of phospholipid molecules with [[phosphate]] heads on the surfaces and [[lipid]] (oil) tails on the inside. The outside heads mix with water, but the tails reject water. Other proteins and lipids can be added to the cell membrane. By these changes, the cell can adjust what it brings in or puts out. Some proteins are always stuck into it, these are called ''integral'' membrane proteins. It also has some which are only sometimes stuck onto it. These are called peripheral membrane proteins. The outer layer protecting the inner cell. == Function == [[Image:Annular Gap Junction Vesicle.jpg|right|thumb|220px| Transmission [[electron microscope]] (TEM) image of a lipid ve