A redox reaction is a chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction. Many important biological processes involve redox reactions. Cellular respiration, for instance, is the oxidation of glucose (C6H12O6) to CO2 and the reduction of oxygen to water. The process of cell respiration also depends heavily on the reduction of NAD+ to NADH and the reverse reaction (the oxidation of NADH to NAD+). In the image below there is a plant that maintains homeostasis by using both photosynthesis and cellular respiration. As mentioned above both of theses processes use redox reactions.