<P> The electron transport chain consists of a spatially separated series of redox reactions in which electrons are transferred from a donor molecule to an acceptor molecule . The underlying force driving these reactions is the Gibbs free energy of the reactants and products . The Gibbs free energy is the energy available ( `` free '' ) to do work . Any reaction that decreases the overall Gibbs free energy of a system is thermodynamically spontaneous . </P>
where does the electron transport chain get its electrons from
donor molecule