The biological function of NADH is to provide an electron source for the electron transport chain/oxidative phosphorylation process in the production of ATP. The biological function of NADPH is: a) to serve as a high energy biomolecule. The hydrolysis of the PO 4 functional group from the molecule releases energy which can be coupled to and "drive" endergonic reactions. b) to serve as an oxidizing agent for metabolic reactions. c) to serve as a reducing agent for metabolic reactions. d) to regulate metabolic reactions by chelating Ca 2 + . .