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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 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 membrane.
From there the NADH and FADH go into the NADH reductase, which produces the enzyme. The NADH pulls the enzyme's electrons to send through the electron transport chain. The electron transport chain pulls H + ions through the chain. From the electron transport chain, the released hydrogen ions make ADP for an result of 32 ATP.
In eukaryotes, the enzymes in this electron transport system use the energy released from O 2 by NADH to pump protons across the inner membrane of the mitochondrion. This causes protons to build up in the intermembrane space , and generates an electrochemical gradient across the membrane.
It is the last enzyme in the respiratory electron transport chain of cells located in the membrane. It receives an electron from each of four cytochrome c molecules and transfers them to one oxygen molecule and four protons , producing two molecules of water.
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.
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.
Any enzyme system that includes cytochrome P450 protein or domain can be called a P450-containing system. [1] [2] [3] [4]P450 enzymes usually function as a terminal oxidase in multicomponent electron-transfer chains, called P450-containing monooxygenase systems, although self-sufficient, non-monooxygenase P450s have been also described.