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Exchange
Definition:
A type of secondary active transport across a biological membrane in which a transport protein couples the movement of an ion (usually Na+ or H+) down its electrochemical gradient to the movement of another ion or molecule against a concentration or electrochemical gradient. The ion moving down its electrochemical gradient is referred to as the driving ion. The ion/molecule being transported against a chemical or electrochemical gradient is referred to as the driven ion/molecule.

In exchange, the driving ion and the driven ion/molecule are transported across the biological membrane in opposite directions.

An example is the Na+/Ca2+ exchanger (NCX), which couples the movement of 3 Na+ ions into the cell down its electrochemical gradient to the movement of 1 Ca2+ ion out of the cell against its electrochemical gradient.

Exchange is also commonly referred to as antiport.

Transport proteins that are involved in this type of transport are referred to as exchangers or antiporters.

See:
Antiport

Related glossary terms/phrases:
Secondary active transport
Cotransport

See also:
Lecture notes on Secondary Active Transport






Posted: Friday, June 27, 2014
Last updated: Friday, June 27, 2014