Primordial cells would have had a similar concept and function to this compartmentalization, although perhaps they did not use the same components as current cells. Their membrane would most likely have been made up of amphiphilic molecules such as fatty acids or perhaps polyprenyl phosphates, similar to modern archaea. However, having a pure lipid bilayer would result in inadequate exchange of charged ions and large polar molecules between the environment and the cell, especially without the use of carrier proteins. Claims have been proposed that cell membranes and membrane proteins co-evolved, meaning that cell membranes shifted from porous to ion-tight, just as membrane proteins shifted from protein amphiphilic pore-forming proteins to very hydrophobic integral membrane proteins. A proposed scheme of this membrane-protein co-development involving the increasing complexity of F- and V-type ATPases and sodium ion transporters with membranes porous to both protons and sodium ions, which become more impermeable to ions, can be observed in Figure 1-5 ( Mulkidjanian et al.