Image 2: Schematically the different stages of the transfer of the copper ion into the cell by the hCTR1 protein. Essential elements are located at the entrance to the conduction channel (gray stars), and are responsible for the selection of the copper ions (yellow circle) over ions and other substances. After a single ion undergoes the selection, the structure of the protein changes, the entrance to the channel is blocked, and additional ions cannot enter. The ion that passed entered the cell, and God forbid returns. . Credit: Maya Shoshan