Upon accepting the hydrogen, NAD+ is converted to its reduced form, NADH. Adequate amounts of NAD must be available to accept the hydrogen atoms that must be removed from glyceraldehyde 3-phosphate if glycolysis is to continue (3,31). How is NAD+ reformed from NADH? There are two ways that the cell restores NAD+ from NADH. First, if sufficient oxygen (O2) is available, the hydrogens from NADH can be ‘shuttled’ into the mitochondria of the cell and can contribute to the aerobic production of ATP(see A Closer Look 3.3) Second, if O2 is not available to accept the hydrogens in the mitochondria, pyruvate can accept the hydrogens to from lactate