ABSTRACT
The electron transport chain and oxidative phosphorylation are the mechanisms by which nicotinamide adenine dinucleotide and flavin adenine dinucleotide are regenerated so that they may be used, again in the tricarboxylic acid cycle. The energy transfer can be looked at chemically as transferring electrons, akin to energy transfer by electricity. The starting compound, NADH is oxidised by losing a pair of electrons, and eventually an oxygen atom is reduced by accepting a pair of electrons. The electrons are either transported from one molecule to the next as hydride ions, a proton with two electrons, or as free electrons. In some mitochondria, the electron transport chain is uncoupled from proton transport. In these cases, the energy generated is used to produce heat. Mitochondria are extraordinarily efficient in extracting energy. This is exemplified by the efficiency of heart tissue in mammals, and in particular the smallest mammal, a species of shrew.
