Antiporter counter-transport

Antiporter, a secondary ion transporter that moves a solute against its electrochemical gradient by using energy derived from the movement of another solute in the opposite direction down its electrochemical gradient. Antiporters are also called exchangers, and the exchange process is sometimes referred to as counter transport. 

Co-transport, also known as symport, is the transport of one compound that is obligatorily linked to that of another. An example is the transport of glucose and Na ions (see below). In counter-transport, also known as antiport, the transporter transports one compound in one direction and... 

B) In secondary translocation reactions, primary bond exchanges or the transfer of electrons do not occur. This class of reactions may be divided into three sub-classes (7) In non-coupled solute translocation, or facilitated diffusion, or uniport reactions, a single solute equilibrates across an osmotic barrier. (2) In sym-coupled solute translocation, or cotransport" , or symport reactions, two solutes equilibrate across an osmotic barrier, and the translocation of one solute is coupled to the translocation of the other in the same direction, (i) In anti-coupled solute translocation, or counter-transport , or antiport reactions, two solutes equilibrate across an osmotic barrier, and the translocation of one solute is coupled to the translocation of the other in the opposite direction. 

It will be seen from Fig. 11 that in the case of countertransport, the steady-state distribution of the driving and driven substrates are such that both are highest on the same side of the membrane A,/A2 = B,/B2, whereas in co-transport the high of the driven substrate is at the opposite face of the membrane to the high of the driving substrate A,/A2 =B2/B,. The two mechanisms have also been called antiport and symport [23] for counter- and co-transport, respectively. 

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