That seems pretty weird your teach said no: Nad IS infact what transports the H+ from extracellular to intracellular..
Could the teach be asking for what "processes" transport it? Such as the krebbs cycle aka citric cycle?
If not the only other thing I can think of (which is fairly in depth and probably NOT the answer) would be Coenzyme Q and Cytochrome C..
Quoted from
http://www.genomeknowledge.org/cgi-bin/eventbrowser?DB=gk_current&ID=163200&ZOOM=2 = "...two electron shuttle molecules; Coenzyme Q (also known as ubiquinone, CoQ) and Cytochrome c (Cytc). These two molecules shuttle electrons between the large complexes in the chain."
Hope this helps D: