Redox potential, also known as reduction potential, measures the tendency of a chemical species to acquire electrons and be reduced. It is expressed in volts and indicates how easily a substance can gain electrons during a redox reaction. A higher redox potential means a greater ability to accept electrons, while a lower potential indicates a stronger tendency to lose electrons. In biological systems, redox potential plays a crucial role in processes like cellular respiration and photosynthesis. For example, in the electron transport chain, the redox potentials of various molecules, such as NADH and O2, determine the flow of electrons and the production of ATP.