Electron transport chain (ETC)
MCAT glossary · Biological & Biochemical Foundations of Living Systems
Definition
Inner-mitochondrial-membrane complexes (I-IV) that shuttle electrons from NADH/FADH_2 to O_2, pumping protons to create the gradient driving ATP synthase (Complex V).
Electron transport chain (ETC) in plain English
This is the final, biggest step of turning food into usable energy, happening in your mitochondria (the cell's power plants). Earlier steps of breaking down food load up two 'delivery trucks' called NADH and FADH_2 with high-energy electrons; the ETC is an assembly line of protein machines (Complexes I–IV) that passes those electrons down the line, eventually handing them to oxygen — which is exactly why you breathe. As electrons move along, the machines pump protons (H⁺) to one side of a membrane, like water piling up behind a dam. That trapped pressure then rushes back through a turbine-like protein (ATP synthase, Complex V), and the spin cranks out ATP, the fuel your cells actually run on.
Also called: ETC
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