Title: Electron transport chain
Content:  Most eukaryotic cells have mitochondria, which produce ATP from products of the citric acid cycle, fatty acid oxidation, and amino acid oxidation. At the inner mitochondrial membrane, electrons from NADH and FADH2 pass through the electron transport chain to oxygen, which provides the energy driving the process as it is reduced to water. The electron transport chain comprises an enzymatic series of electron donors and acceptors. Each electron donor will pass electrons to a more electronegative acceptor, which in turn donates these electrons to another acceptor, a process that continues down the series until electrons are passed to oxygen, the most energy-rich and terminal electron acceptor in the chain. Each reaction between a donor and an acceptor releases energy, which via the transferred electrons is used to generate a proton gradient across the mitochondrial membrane by "pumping" protons into the intermembrane space, producing a state of higher free energy that has the potential to do work. This entire process is called oxidative phosphorylation since ADP is phosphorylated to ATP by using the electrochemical gradient established by the redox reactions of the electron transport chain.
Title: Quantum biology
Content:  carbohydrates and fats. This process utilizes electrons in an electron transport chain (ETP). The genealogy of electron transport proceeds as follows: Electrons from NADH are transferred to NADH dehydrogenase (complex I protein), which is located in the IMM. Electrons from complex I are transferred to coenzyme Q to make CoQH2; next, electrons flow to cytochrome-containing IMM protein (complex III), which further pushes electrons to cytochrome c, where electrons flow to complex IV; complex IV is the final IMM protein complex of the ETC respiratory chain. This final protein allows electrons to reduce oxygen from an O2 molecule to a single O, so that it can bind to the hydrogen ions to produce H2O. The energy produced from 
Title: Electron transport chain
Content:  In eukaryotes, NADH is the most important electron donor. The associated electron transport chain is NADH → Complex I → Q → Complex III → cytochrome c → Complex IV → O2 where Complexes I, III and IV are proton pumps, while Q and cytochrome c are mobile electron carriers. The electron acceptor is molecular oxygen. In prokaryotes (bacteria and archaea) the situation is more complicated, because there are several different electron donors and several different electron acceptors. The generalized electron transport chain in bacteria is: Donor           Donor                    Donor ↓               ↓                        ↓                  dehydrogenase   →   quinone   →   bc1   →   cytochrome ↓                       ↓                                 oxidase(reductase)       oxidase(reductase) ↓                       ↓                                      Acceptor                 Acceptor Electrons can enter the chain at three levels: at the level of a dehydrogenase, at the level of the quinone pool, or at the level of a mobile cytochrome electron carrier. These levels correspond to successively more positive redox potentials, 
Title: Electron transport chain
Content:  The electron transport chain (ETC; respiratory chain ) is a series of protein complexes that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. The electron transport chain is built up of peptides, enzymes, and other molecules. The flow of electrons through the electron transport chain is an exergonic process. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP). In aerobic respiration, the flow of electrons terminates with molecular oxygen being the final electron acceptor. In anaerobic respiration, other electron acceptors are used, such as 
Title: Electron transport chain
Content:  membrane. The energy released by the reaction of oxygen with reduced compounds such as cytochrome c and (indirectly) NADH and FADH is used by the electron transport chain to pump protons into the intermembrane space, generating the electrochemical gradient over the inner mitochondrial membrane. In photosynthetic eukaryotes, the electron transport chain is found on the thylakoid membrane. Here, light energy drives the reduction of components of the electron transport chain and therefore causes subsequent synthesis of ATP. In bacteria, the electron transport chain can vary over species but it always constitutes a set of redox reactions that are coupled to the synthesis of ATP, through the generation of an electrochemical gradient, and oxidative phosphorylation through ATP synthase.
Title: Electron transport chain
Content:  In oxidative phosphorylation, electrons are transferred from a moderate-energy electron donor such as NADH to a high-energy acceptor such as O2 through an electron transport chain, releasing the energy. In photophosphorylation, the energy of sunlight is used to create a high-energy electron donor which can subsequently reduce oxidized components that are then coupled to ATP synthesis via proton translocation by the electron transport chain. Photosynthetic electron transport chains, like the mitochondrial chain, can be considered as a special case of the bacterial systems. They use mobile, lipid-soluble quinone carriers (phylloquinone and plastoquinone) and mobile, water-soluble carriers (cytochromes, electron transport chain.). They also contain a proton pump. The proton pump in all photosynthetic chains resembles mitochondrial Complex III. The commonly-held theory of symbiogenesis proposes that both organelles descended from bacteria.
Title: Electron transport chain
Content:  Cytochromes are pigments that contain iron. They are found in two very different environments. Some cytochromes are water-soluble carriers that shuttle electrons to and from large, immobile macromolecular structures imbedded in the membrane. The mobile cytochrome electron carrier in mitochondria is cytochrome c. Bacteria use a number of different mobile cytochrome electron carriers. Other cytochromes are found within macromolecules such as Complex III and Complex IV. They also function as electron carriers, but in a very different, intramolecular, solid-state environment. Electrons may enter an electron transport chain at the level of a mobile cytochrome or quinone carrier. For example, electrons from inorganic electron donors (nitrite, ferrous iron, electron transport chain) enter the electron transport chain at the cytochrome level. When electrons enter at a redox level greater than NADH, the electron transport chain must operate in reverse to produce this necessary, higher-energy molecule.
Title: Mitochondrion
Content:   The electrons from NADH and FADH2 are transferred to oxygen (O2), an energy-rich molecule, and hydrogen (protons) in several steps via the electron transport chain. NADH and FADH2 molecules are produced within the matrix via the citric acid cycle but are also produced in the cytoplasm by glycolysis. Reducing equivalents from the cytoplasm can be imported via the malate-aspartate shuttle system of antiporter proteins or feed into the electron transport chain using a glycerol phosphate shuttle. Protein complexes in the inner membrane (NADH dehydrogenase (ubiquinone), cytochrome c reductase, and cytochrome c oxidase) perform the transfer, and the incremental release of energy is used to pump protons (H+) into the intermembrane space. This process is efficient, but a small percentage of electrons may prematurely reduce oxygen, forming 
Title: Oxidative phosphorylation
Content:  The electron transport chain carries both protons and electrons, passing electrons from donors to acceptors, and transporting protons across a membrane. These processes use both soluble and protein-bound transfer molecules. In mitochondria, electrons are transferred within the intermembrane space by the water-soluble electron transfer protein cytochrome c. This carries only electrons, and these are transferred by the reduction and oxidation of an iron atom that the protein holds within a heme group in its structure. Cytochrome c is also found in some bacteria, where it is located within the periplasmic space. Within the inner mitochondrial membrane, the lipid-soluble electron carrier coenzyme Q10 (Q) carries both electrons and protons by a redox cycle. This small benzoquinone 
Title: Electron transport chain
Content:  Energy associated with the transfer of electrons down the electron transport chain is used to pump protons from the mitochondrial matrix into the intermembrane space, creating an electrochemical proton gradient (ΔpH) across the inner mitochondrial membrane. This proton gradient is largely but not exclusively responsible for the mitochondrial membrane potential (ΔΨM). It allows ATP synthase to use the flow of H+ through the enzyme back into the matrix to generate ATP from adenosine diphosphate (ADP) and inorganic phosphate. Complex I (NADH coenzyme Q reductase; labeled I) accepts electrons from the Krebs cycle electron carrier nicotinamide adenine dinucleotide (NADH), and passes them to coenzyme Q (ubiquinone; labeled Q), which also receives electrons from complex II (succinate dehydrogenase; labeled II). Q passes electrons to complex 

Question: where does the electron transport chain get its electrons from?
Answer: electron donors.
donor molecule.