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transport
(redirected from active transport)

   Also found in: Dictionary/thesaurus, Medical, Legal, Financial, Wikipedia, Hutchinson 0.07 sec.

transport

In biochemistry, the movement of molecules and particles across a cell membrane, a selective barrier that allows some substances (fat-soluble molecules and some small molecules) to pass and blocks others (ions and large, water-soluble molecules). Transport of these vital substances occurs via several systems. Open channels allow diffusion (passive transport) of ions directly into cells; facilitators use a chemical change to help substances diffuse past the membrane; “pumps” force dilute substances through even when their concentration on the other side is higher (a form of active transport). Primary active transport is powered directly by energy released in cell metabolism (see ATP, adenosine triphosphate). In secondary active transport, a molecule is linked to a different molecule that carries it across the membrane (cotransport) or is exchanged for a different molecule crossing in the other direction (countertransport). The membrane itself opens and closes to let larger particles in or out.


To move or copy from one location to another. Same as "transfer." In the physical world, "to transport" means "to move" (take this from here and put it there). In the electronic world, "to transport" means "to copy" the data to another location. The original data is still intact in its first location until it is purposely deleted. See transport layer and OSI.


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? Mentioned in ? References in periodicals archive
 
This finding was consistent with an active transport mechanism across the placenta.
Others have suggested that nitrate or the reduced form (nitrite) may pass to the fetus through a system of active transport similar to that of iodide, and fetal nitrate plasma levels may exceed that of the mother (Hartman 1982).
Interestingly, from a separate questionnaire sent home for parents to complete, the majority of parents (77%) stated they either walked or cycled to school themselves as 10-year-olds, indicating a substantial decrease in active transport in only one generation.
 
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