What is electron transport?
Not knowing what your background is, I'll give an overview of the process in the mitochondrion. A similar process occurs in the chloroplasts as well, although as part of photosynthesis.
NADH and FADH2 that are produced by glycolysis, the citric acid cycle and fatty acid oxidation are oxidized by the respiratory electron-transport chain in the mitochondrion. Essentially, electrons are passed from NADH and FADH2 through a series of intermediaries, to molecular oxygen -- O2. As a result, O2 is reduced to form water. In the mitochondrion, the electron transport chain exists in the inner membrane (for eukaryotic cells). Three of the protein complexes in the electron transport chain are proton-pumping stations. They function to pump protons, H+ ions, across the inner mitochondrial membrane, from the matrix to the inner membrane space. They pump protons up their concentration gradient and up their electrical ...
This solution is provided in 593 words. It explains electron transfer process in the mitochondrion in detail, including describing the electrochemical gradient and proton gradient.