Electron Transport Chain: A series of protein complexes and small organic molecules embedded in the inner mitochondrial membrane that transfers electrons from donors to acceptors via redox reactions, and couples this with the transfer of protons across a membrane.
Krebs Cycle: Also known as citric acid cycle or TCA cycle, it's a series of chemical reactions used by all aerobic organisms to release stored energy through oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins into ATP and carbon dioxide.
NADH: Similar to FADH2, NADH is another high-energy molecule that carries electrons from one reaction to another.