Uniport translocation

Membrane potential and pH gradient are always determined separately. Since a membrane potential is a delocalized parameter for a given membrane, it follows that the membrane potential generated by the translocation of protons across the membrane will be felt by all ions distributed across the membrane. If an electrical uniport pathway exists for one of these ions, then it will tend to come to an equilibrium when its electrochemical potential gradient is zero ... 

Transporters genes encode proteins, generally constituted by 12 transmembrane spanning regions. These mediated Na+ or H+ dependent accumulation of small molecules such as neurotransmitters, antibiotics, ions and cationic amino-acid transporters into the cells or organelles. The transport is performed by different mechanisms uniport, substrate-ion sym-port, substrate-ion antiport, substrate-substrate or ion-ion antiport, and ATP-dependent translocation. 

Mitchell [7] visualized three different systems for facilitated secondary transport. Uniport only one solute is translocated by the carrier protein. Symport two or more different solutes are translocated in the same direction by the carrier protein. Antiport two or more different solutes are translocated by one carrier in opposite directions. 

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. 

Although there is still some difference of opinion, it is probable that further studies on valinomycin and gramicidins A, B, and C will confirm that they are uniport catalysts of the pore or single chemieal channel type (ref. 36) and that whereas valinomycin has a rather high specificity for K" " translocation and discriminates against ions, owing to the effectively... 

Plant mitochondria, in contrast to animal mitochondria, contain specific translocators for malate and oxaloacetate operating as electrogenic uniports (11). The uptake of OAA into mitochondria from spinach leaves... 

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