Paul Saladino· MD
fad is the other energy consuming substrate energy carrying substrate um and classically there it's shown in complex two and you can't the the body doesn't have a supply of fad or fadh2 it's almost invariably embedded in a protein you can't just take it out and shift it around you can't transport it in or out of a mitochondrion and you can't buy it off the shelf there's a reagent grade drug it's embedded in protein almost every instance i can think of