<span>Most membrane channels allow passage by simple diffusion of small inorganic ions of a specific type and may also be voltage gated. The solute binds to a protein carrier on one side of the membrane and is released on the other side after the transporter undergoes a change in shape, the movement of molecules across a cell membrane from a region of their lower concentration to a region of their higher concentration in the direction against some gradient or other obstructing factor.</span>
