Any Molecular Entity That Serves As an Electron Acceptor and Electron Donor in an Electron Transport Chain. an Electron Transport Chain Is a Process in Which a Series of Electron Carriers Operate Together to Transfer Electrons From Donors to Any of Several Different Terminal Electron Acceptors to Generate a Transmembrane Electrochemical Gradient.
Interacting Selectively and Non Covalently with a Transition Metal Ions; a Transition Metal Is an Element Whose Atom Has an Incomplete D Subshell of Extranuclear Electrons or Which Gives Rise to a Cation or Cations with an Incomplete D Subshell. Transition Metals Often Have More Than One Valency State. Biologically Relevant Transition Metals Include Vanadium Manganese Iron Copper Cobalt Nickel Molybdenum and Silver.