Electron transfer chain

From Freepedia

The electron transfer chain (also called the electron transport chain, ETC, e-train, or simply electron transport), is any series of protein complexes and lipid-soluble messengers that convert the reductive potential of energized electrons into a cross-membrane proton gradient.

Contents 1 How it works 2 Five complexes 2.1 Complex I (proton pump) 2.2 Complex II 2.3 Complex III (proton pump) 2.4 Cytochrome c 2.5 Complex IV (proton pump) 2.6 Complex V 3 Inhibition 4 See also 5 External links

How it works

This proton motive force created by the ETC is used to power membrane transporters and adenosine triphosphate synthesis by ATP synthase (aka the F_oF₁ particle). They are used in photophosphorylation and respiration.

In eukaryotes, including humans, an ETC is found spanning the inner mitochondrial membrane (crista) and accepts electrons from electron donors such as NADH or succinate, shuttles these electrons from within the mitochondrial matrix across the inner mitochondrial membrane into the intermembrane space, where they ultimately reduce oxygen.

Five complexes

There are five complexes normally associated with the mitochondrial electron transfer chain. All of these are proteolipid complexes, with the first four containing either flavins, iron-sulfur clusters, copper centers, or heme moieties.

Complex I (proton pump)

NADH dehydrogenase, also called NADH coenzyme Q reductase.

Complex II

Succinate - coenzyme Q reductase. Complex II is part of the Krebs cycle and does not pump protons.

Complex III (proton pump)

Coenzyme Q - cytochrome c reductase.

Cytochrome c

Cytochrome c is also an essential part of the electron transfer chain. It is a soluble protein loosely associated with the inner mitochondrial membrane, and transfers electrons between Complexes III and IV.

Complex IV (proton pump)

Cytochrome c oxidase. Complex IV is the terminus of the electron transfer chain, where oxygen from the lungs is reduced by electrons and hydrogen protons (provided by NADH and/or FADH2) to make water.

Complex V

ATP synthase, also known as the F_oF₁ particle. Complex V uses the electrochemical potential generated to create ATP.

Inhibition

The electron transfer chain can be inhibited by various poisons. Among them we can cite carbon monoxide, cyanide, azide, antimycin, amytal and rotenone.

See also

• cytochrome
• mitochondrion
• chloroplast

External links

• animated overview of mitochondria and electron transport chain
• gif animation
• Image of complexes
• Overview and flash animation
• Tutorial