Problem: When something is oxidized, it _____ electrons and when somethins is reduced, it _____ electrons.A. gains; losesB. loses; gainsC. gains; gainsD. loses; loses

Many metabolic reactions proceed simply through the transfer of electrons. In these reactions, the transfer of electrons is always coupled: one component of the reaction loses electrons (electron source) and another component gains these electrons (electron sink). These coupled reactions are known as redox reactions.