Ubiquinone Is One of Two Mobile Electron Carriers in the Electron-Transport

Multiple Choice

Ubiquinone is one of two mobile electron carriers in the electron-transport chain.Where does the additional pair of electrons reside in the reduced ubiquinone molecule?

A) The electrons are added directly to the aromatic ring.
B) The electrons are added to each of two ketone oxygens on the aromatic ring.
C) The electrons are added to the hydrocarbon tail, which hides them inside the membrane bilayer.
D) Both electrons, and one proton, are added to a single ketone oxygen bound to the aromatic ring.