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An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which 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.
Characterization of transport properties requires fabricating a device and measuring its current-voltage characteristics. Devices for transport studies are typically fabricated by thin film deposition or break junctions. The dominant transport mechanism in a measured device can be determined by differential conductance analysis.
Electron transfer (ET) occurs when an electron relocates from an atom, ion, or molecule, to another such chemical entity. ET describes the mechanism by which electrons are transferred in redox reactions.
The chain of redox reactions driving the flow of electrons through the electron transport chain, from electron donors such as NADH to electron acceptors such as oxygen and hydrogen (protons), is an exergonic process – it releases energy, whereas the synthesis of ATP is an endergonic process, which requires an input of energy.
The electron transport chain is responsible for establishing a pH and electrochemical gradient that facilitates the production of ATP through the pumping of protons. The gradient also provides control of the concentration of ions such as Ca 2+ driven by the mitochondrial membrane potential. [ 1 ]
In cellular biology, active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement.
Considering the microscopic transport (transport is a results of nonequilibrium), = ′ = (), = ′ = () (), where u e is the electron velocity vector, f e ( f e o ) is the electron nonequilibrium (equilibrium) distribution, τ e is the electron scattering time, E e is the electron energy, and F te is the electric and thermal forces from ∇( E ...
Complex III itself is composed of several subunits, one of which is a b-type cytochrome while another one is a c-type cytochrome. Both domains are involved in electron transfer within the complex. Complex IV contains a cytochrome a/a3-domain that transfers electrons and catalyzes the reaction of oxygen to water.