In modern chemistry and biochemistry, a hydride is a molecule consisting of one proton and two electrons. In many bioelectrochemical processes, a hydride transfer either originates or ends up at NADH, NADPH or one of the flavin cofactors. Whether the overall hydride transfer happens all at once (a concerted mechanism) or happens in an electron-proton-electron stepwise manner is a topic of much current debate among biophysicists and biochemists.