Other substances, completely lacking amino acids, are also capable of channel-formation. 2.B. Non-ribosomally synthesized porters. They complex a cation in their hydrophilic interior and facilitate translocation of the complex across the membrane, exposing their hydrophobic exterior, by moving from one side of the bilayer to the other. If the free porter can cross the membrane in the uncomplexed form, the transport process can be electrophoretic, but if only the complex crosses the membrane, transport is electroneutral. 2.C. Ion gradient-driven energizers.
Homologous energizers drive bacterial flagellar motility.
Primary Active Transporters. These transporters use a primary source of energy to drive active transport of a solute against a concentration gradient. A secondary ion gradient is not considered a primary energy source because it is created by the expenditure of a primary energy source. Primary energy sources known to be coupled to transport are chemical, electrical and solar. The transport protein may or may not be transiently phosphorylated, but the substrate is not phosphorylated.