Otto Heinrich Warburg studied the chemistry of the fermentation reactions and discovered that the co-enzyme is needed for a certain type of chemical reaction, called a hydride transfer. Hydride transfer reactions involve the exchange of a hydrogen atom and its accompanying electrons. These types of reactions are essential to cellular metabolism and many other chemical processes that are required to sustain life. Warburg’s work showed that, in fermentation, the nicotinamide part of NAD accepts the hydride and allows the reaction to proceed.;jsessionid=D2B68185EB94A3AC0344DE1C28509E6B.f02t03