An electron donor is a substance or molecule that donates one or more electrons to another substance
in a chemical reaction. In biological systems, electron donors are typically involved in redox reactions, inwhich electrons are transferred from the donor to an electron acceptor. During cellular respiration, for example, glucose is an electron donor that donates electrons to electron carriers such as NADH and
FADH2. These electron carriers then transfer the electrons to the electron transport chain, where they
are ultimately transferred to the terminal electron acceptor (such as oxygen) to generate ATP.