Final answer:
The Electron Transport Chain (ETC) allows organisms to extract energy-rich compounds by transferring electrons through a series of molecules in the inner membrane of the mitochondrion and using the resulting electrochemical gradient to synthesize ATP.
Step-by-step explanation:
The Electrons Transport Chain (ETC) is a series of molecules in the inner membrane of the mitochondrion that transfers electrons from molecule to molecule through chemical reactions. As the electrons flow through these molecules, some of the energy is used to pump hydrogen ions (H+) across the inner membrane, creating an electrochemical gradient. This gradient is used to synthesize ATP, the energy-rich compound that the organism can extract from the ETC.