The voltage difference that results, called the membrane potential, stores potential energy that can be released later. Blocking that flow, for example with a cell membrane, stores up electrical potential energy. By controlling the natural current and letting positive or negative charge build up on either side of their membranes, cells maintain their membrane potential. But researchers interested in these tissues typically study mechanical forces, chemical signaling, and gene expression — not currents and voltage, Rosenblatt said. There, natural currents of positively charged protons could have served as a kind of primordial membrane potential and powered prebiotic chemical reactions.