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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.
The energy transferred by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport. This generates potential energy in the form of a pH gradient and the resulting electrical potential across this membrane.
NADH/ubiquinone oxidoreductase, also known as complex I, is the first and largest protein in the mitochondrial respiratory chain. It consists of a membrane arm, embedded inside the inner mitochondrial membrane, and a matrix arm, extending out of the membrane. There are 78 transmembrane helices and three proton pumps.
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]
The mitochondrial shuttles are biochemical transport systems used to transport reducing agents across the inner mitochondrial membrane. NADH as well as NAD+ cannot cross the membrane, but it can reduce another molecule like FAD and [QH 2] that can cross the membrane, so that its electrons can reach the electron transport chain.
These electrons enter the electron transport chain of the mitochondria via reduction equivalents to generate ATP. The shuttle system is required because the mitochondrial inner membrane is impermeable to NADH, the primary reducing equivalent of the electron transport chain. To circumvent this, malate carries the reducing equivalents across the ...
The Q cycle (named for quinol) describes a series of sequential oxidation and reduction of the lipophilic electron carrier Coenzyme Q (CoQ) between the ubiquinol and ubiquinone forms. These reactions can result in the net movement of protons across a lipid bilayer (in the case of the mitochondria, the inner mitochondrial membrane).
NADH is oxidized into NAD +, H + ions, and electrons by an enzyme. FADH 2 is also oxidized into H + ions, electrons, and FAD.As those electrons travel farther through the electron transport chain in the inner membrane, energy is gradually released and used to pump the hydrogen ions from the splitting of NADH and FADH 2 into the space between the inner membrane and the outer membrane (called ...