促進輸送、媒介輸送

WordNet

move something or somebody around; usually over long distances
an exchange of molecules (and their kinetic energy and momentum) across the boundary between adjacent layers of a fluid or across cell membranes
move while supporting, either in a vehicle or in ones hands or on ones body; "You must carry your camping gear"; "carry the suitcases to the car"; "This train is carrying nuclear waste"; "These pipes carry waste water into the river" (同)carry
transport commercially (同)send, ship
increase the likelihood of (a response); "The stimulus facilitates a delayed impulse"
make easier; "you could facilitate the process by sharing your knowledge" (同)ease, alleviate

PrepTutorEJDIC

(ある場所からある場所へ)…‘を'『輸送する』,運搬する《+名+from+名+to+名》 / 《文》《受動態で》(…で)…‘を'夢中にする,有頂天にする《+名+with+名》 / 〈罪人〉‘を'流刑にする / 〈U〉輸送,運送,輸送(交通)機関(transportation) / 〈C〉(軍隊や軍需品を運ぶ)輸送船,輸送機
…‘を'容易にする,楽にする,助ける,促進する

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/24 03:04:03」(JST)

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Facilitated diffusion in cell membrane, showing ion channels and carrier proteins

Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins.^[1] Being passive, facilitated transport does not directly require chemical energy from ATP hydrolysis in the transport step itself; rather, molecules and ions move down their concentration gradient reflecting its diffusive nature.

Facilitated diffusion is different from free diffusion in several ways. First, the transport relies on molecular binding between the cargo and the membrane-embedded channel or carrier protein. Second, the rate of facilitated diffusion is saturable with respect to the concentration difference between the two phases; unlike free diffusion which is linear in the concentration difference. Third, the temperature dependence of facilitated transport is substantially different due to the presence of an activated binding event, as compared to free diffusion where the dependence on temperature is mild.^[2]

3D rendering of facilitated diffusion

Polar molecules and large ions dissolved in water cannot diffuse freely across the plasma membrane due to the hydrophobic nature of the fatty acid tails of the phospholipids that make up the lipid bilayer. Only small, non-polar molecules, such as oxygen and carbon dioxide, can diffuse easily across the membrane. Hence, no nonpolar molecules are transported by proteins in the form of transmembrane channels. These channels are gated, meaning that they open and close, and thus deregulate the flow of ions or small polar molecules across membranes, sometimes against the osmotic gradient. Larger molecules are transported by transmembrane carrier proteins, such as permeases, that change their conformation as the molecules are carried across (e.g. glucose or amino acids). Non-polar molecules, such as retinol or lipids, are poorly soluble in water. They are transported through aqueous compartments of cells or through extracellular space by water-soluble carriers (e.g. retinol binding protein). The metabolites are not altered because no energy is required for facilitated diffusion. Only permease changes its shape in order to transport metabolites. The form of transport through a cell membrane in which a metabolite is modified is called group translocation transportation.

Glucose, sodium ions, and chloride ions are just a few examples of molecules and ions that must efficiently cross the plasma membrane but to which the lipid bilayer of the membrane is virtually impermeable. Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass mechanism.

Various attempts have been made by engineers to mimic the process of facilitated transport in synthetic (i.e., non-biological) membranes for use in industrial-scale gas and liquid separations, but these have met with limited success to date, most often for reasons related to poor carrier stability and/or dissociation of the carrier from the membrane.

References

^ Pratt, Charlotte Amerley; Voet, Donald; Voet, Judith G. (2002). Fundamentals of biochemistry upgrade. New York: Wiley. pp. 264–266. ISBN 0-471-41759-9.
^ Friedman, Morton (2008). Principles and models of biological transport. Springer. ISBN 978-0387-79239-2.

External links

Facilitated Diffusion - Description and Animation
Facilitated Diffusion- Definition and Supplement

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UpToDate Contents

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1. 胎盤の発達および生理学 placental development and physiology
2. 微生物標本の収集および輸送 microbiology specimen collection and transport
3. 脳脊髄液：疾患状態における検査の生理学および有用性 cerebrospinal fluid physiology and utility of an examination in disease states
4. 経口補水療法 oral rehydration therapy
5. 危篤状態の成人患者における疼痛管理 pain control in the critically ill adult patient

English Journal

Membrane transport metabolons.

Moraes TF, Reithmeier RA.AbstractIn this review evidence from a wide variety of biological systems is presented for the genetic, functional, and likely physical association of membrane transporters and the enzymes that metabolize the transported substrates. This evidence supports the hypothesis that the dynamic association of transporters and enzymes creates functional membrane transport metabolons that channel substrates typically obtained from the extracellular compartment directly into their cellular metabolism. The immediate modification of substrates on the inner surface of the membrane prevents back-flux through facilitated transporters, increasing the efficiency of transport. In some cases products of the enzymes are themselves substrates for the transporters that efflux the products in an exchange or antiport mechanism. Regulation of the binding of enzymes to transporters and their mutual activities may play a role in modulating flux through transporters and entry of substrates into metabolic pathways. Examples showing the physical association of transporters and enzymes are provided, but available structural data is sparse. Genetic and functional linkages between membrane transporters and enzymes were revealed by an analysis of Escherichia coli operons encoding polycistronic mRNAs and provide a list of predicted interactions ripe for further structural studies. This article supports the view that membrane transport metabolons are important throughout Nature in organisms ranging from bacteria to humans.
Biochimica et biophysica acta.Biochim Biophys Acta.2012 Nov;1818(11):2687-706. Epub 2012 Jun 13.
In this review evidence from a wide variety of biological systems is presented for the genetic, functional, and likely physical association of membrane transporters and the enzymes that metabolize the transported substrates. This evidence supports the hypothesis that the dynamic association of trans
PMID 22705263

Facilitated diffusion of VEGF165 through descemet's membrane with sucrose octasulfate.

Fannon M, Forsten-Williams K, Zhao B, Bach E, Parekh PP, Chu CL, Goerges-Wildt AL, Buczek-Thomas JA, Nugent MA.SourceDepartment of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, Kentucky. michael.fannon@uky.edu.
Journal of cellular physiology.J Cell Physiol.2012 Nov;227(11):3693-700. doi: 10.1002/jcp.24077.
Vascular endothelial growth factor A (VEGF-A) is a promoter of neovascularization and thus a popular therapeutic target for diseases involving excessive growth of blood vessels. In this study, we explored the potential of the disaccharide sucrose octasulfate (SOS) to alter VEGF165 diffusion through
PMID 22378222