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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/06 05:10:36」(JST)

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This article is about various membranes in living things. For the membranes surrounding cells, see cell membrane.

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 membrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content.^[1] The cellular membranes should not be confused with isolating tissues formed by layers of cells, such as mucous and basement membranes.

Function

Membranes in cells typically define enclosed spaces or compartments in which cells may maintain a chemical or biochemical environment that differs from the outside. For example, the membrane around peroxisomes shields the rest of the cell from peroxides, and the cell membrane separates a cell from its surrounding medium. Most organelles are defined by such membranes, and are called "membrane-bound" organelles.

Probably the most important feature of a biomembrane is that it is a selectively permeable structure. This means that the size, charge, and other chemical properties of the atoms and molecules attempting to cross it will determine whether they succeed in doing so. Selective permeability is essential for effective separation of a cell or organelle from its surroundings. Biological membranes also have certain mechanical or elastic properties.

Particles that are required for cellular function but are unable to diffuse freely across a membrane enter through a membrane transport protein or are taken in by means of endocytosis.

Diversity of biological membranes

Many types of specialized plasma membranes can separate cell from external environment: apical, basolateral, presynaptic and postsynaptic ones, membranes of flagella, cilia, microvillus, filopodia and lamellipodia, the sarcolemma of muscle cells, as well as specialized myelin and dendritic spine membranes of neurons. Plasma membranes can also form different types of "supramembrane" structures such as caveola, postsynaptic density, podosome, invadopodium, desmosome, hemidesmosome, focal adhesion, and cell junctions. These types of membranes differ in lipid and protein composition.

Distinct types of membranes also create intracellular organelles: endosome; smooth and rough endoplasmic reticulum; sarcoplasmic reticulum; Golgi apparatus; lysosome; mitochondrion (inner and outer membranes); nucleus (inner and outer membranes); peroxisome; vacuole; cytoplasmic granules; cell vesicles (phagosome, autophagosome, clathrin-coated vesicles, COPI-coated and COPII-coated vesicles) and secretory vesicles (including synaptosome, acrosomes, melanosomes, and chromaffin granules).

Different types of biological membranes have diverse lipid and protein compositions. The content of membranes defines their physical and biological properties. Some components of membranes play a key role in medicine, such as the efflux pumps that pump drugs out of a cell.

References

^ Mark L. Latash (2007). Neurophysiological basis of movement. Human Kinetics Publishers. ISBN 978-0-7360-6367-8.
^ UpToDate Patient Preview > Fetal membranes: Anatomy and biochemistry Author: Seth Guller, PhD. Retrieved on Mars 7, 2010

von Heijne G, Rees D (August 2008). "Membranes: reading between the lines". Curr. Opin. Struct. Biol. 18 (4): 403–5. doi:10.1016/j.sbi.2008.06.003. PMID 18634876. http://linkinghub.elsevier.com/retrieve/pii/S0959-440X(08)00091-2.

External links

Membranes at the US National Library of Medicine Medical Subject Headings (MeSH)

English Journal

Biochemistry of uridine in plasma.

Yamamoto T, Koyama H, Kurajoh M, Shoji T, Tsutsumi Z, Moriwaki Y.AbstractUridine is a pyrimidine nucleoside that plays a crucial role in synthesis of RNA, glycogen, and biomembrane. In humans, uridine is present in plasma in considerably higher quantities than other purine and pyrimidine nucleosides, thus it may be utilized for endogenous pyrimidine synthesis. Uridine has a number of biological effects on a variety of organs with or without disease, such as the reproductive organs, central and peripheral nervous systems, and liver. In addition, it is used in clinical situations as a rescue agent to protect against the adverse effects of 5-fluorouracil. Since the biological actions of uridine may be related to its plasma concentration, it is important to examine factors that have effects on that concentration. Factors associated with an increase in plasma concentration of uridine include enhanced ATP consumption, enhanced uridine diphosphate (UDP)-glucose consumption via glycogenesis, inhibited uridine uptake by cells via the nucleoside transport pathway, increased intestinal absorption, and increased 5-phosphribosyl-1-pyrophosphate and urea synthesis. In contrast, factors that decrease the plasma concentration of uridine are associated with accelerated uridine uptake by cells via the nucleoside transport pathway and decreased pyrimidine synthesis.
Clinica chimica acta; international journal of clinical chemistry.Clin Chim Acta.2011 Sep 18;412(19-20):1712-24. Epub 2011 Jun 14.
Uridine is a pyrimidine nucleoside that plays a crucial role in synthesis of RNA, glycogen, and biomembrane. In humans, uridine is present in plasma in considerably higher quantities than other purine and pyrimidine nucleosides, thus it may be utilized for endogenous pyrimidine synthesis. Uridine ha
PMID 21689643

Cholesterol attenuates and prevents bilayer damage and breakdown in lipoperoxidized model membranes. A spin labeling EPR study.

Megli FM, Conte E, Ishikawa T.SourceDipartimento di Biochimica e Biologia Molecolare "E. Quagliariello", Universita di Bari, e Istituto di Biomembrane e Bioenergetica, CNR, Via E. Orabona, 4-70126 Bari, Italy.
Biochimica et biophysica acta.Biochim Biophys Acta.2011 Sep;1808(9):2267-74. Epub 2011 May 7.
The stabilizing effect of cholesterol on oxidized membranes has been studied in planar phospholipid bilayers and multilamellar 1-palmitoyl-2-linoleoyl-phosphatidylcholine vesicles also containing either 1-palmitoyl-2-glutaroyl-phosphatidylcholine or 1-palmitoyl-2-(13-hydroxy-9,11-octadecanedienoyl)-
PMID 21600189

Japanese Journal

Lipid Mediators in Life Science

MURAKAMI Makoto
Experimental Animals 60(1), 7-20, 2011
"Lipid mediators" represent a class of bioactive lipids that are produced locally through specific biosynthetic pathways in response to extracellular stimuli. They are exported extracellularly, bind t …
NAID 130000419262

One-step direct reconstitution of biomembranes onto cationic organic polymer bead supports.

Osei-Asante Samuel,Haratake Mamoru,Fuchigami Takeshi,Nakayama Morio
Journal of colloid and interface science 351(1), 96-101, 2010-11-01
In this study, we addressed the straightforward reconstitution of red blood cell (RBC) membranes on the surface of cationic organic polymer beads. The RBC membrane-bead complex was obtained by the inc …
NAID 120002400753