The bicarbonate ( ) exits at the basal portion of the cell via sodium ( ) symport and chloride ( ) antiport and re-enters circulation, where it may accept a proton if blood pH decreases, thus acting as a weak, basic buffer.
12.
Antiport and symport processes are associated with secondary active transport, meaning that one of the two substances is transported in the direction of its concentration gradient, utilizing the energy derived from the transport of such substance ( mostly Na, K or H ions ) down its concentration gradient.
13.
Overexpressing a vacuolar Na + / H + antiport ( " AtNHX1 " ) from " A . thaliana " lead to salt accumulating in the leaves of the plants, but not in the fruit and allowed them to grow more in salt solutions than wildtype plants.
14.
ArsA homologues are found in bacteria, archaea and eukarya ( both animals and plants ), but there are far fewer of them in the databases than ArsB proteins, suggesting that many ArsB homologues function by a pmf-dependent mechanism, probably an arsenite : H + antiport mechanism.
15.
Proteins of the "'Betaine / Carnitine / Choline Transporter ( BCCT ) family "'( TC # 2 . A . 15 ) are found in pmf-driven or smf-driven proton or sodium ion symport, respectively, or else by substrate : substrate antiport.
