Metabolism

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The electron transport chain

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The electron transport chain is a chain of

complexes and

mobile carriers that act as electron carriers.

The membrane complexes are NADH dehydrogenase complex, cytochrome b-c1 complex and cytochrome oxidase

The mobile carriers are ubiquinone and

The above proteins accept electron and a proton from the aqueous solution. Each unit of the chain has a

affinity for electrons, allowing them to flow in a logical order.

The chain runs from NADH dehydrogenase to

to cytochrome b-c1 to

and finally to cytochrome oxidase. As electrons pass through each of the membrane complexes, protons are pumped to the inter-membranous space

NADH dehydrogenase

NADH to give NAD+. A proton is pumped out in the process. The electron is passed onto ubiquinone which is reduced to form

which passes the electron to cytochrome b-c1. A proton is pumped out and ubiquinol is oxidised back to ubiquinone.

Then the electron is passed to cytochrome c which passes it to cytochrome oxidase. This pumps out a proton and passes the electron to oxygen, which accepts protons from the matrix and becomes

Ubiquinone is a mobile carrier of electrons, it can pick either one or two electrons with a proton from solution and passes them to cytochrome b-c1 complex. It has a hydrophobic

that confines it to the lipid bilayer of the membrane where it is needed

Succinate dehydrogenase, an enzyme of the Krebs cycle is an integral membrane proton that is attached to the

where it can immediately communicate with

FADH2, generated in the step that is catalysed by succinate dehydrogenase directly donated its electrons to

so less protons are pumped out of the matrix to the intramembranous space thus less ATP is generated from the reduction of FADH2 than NADH

Cytochrome c oxidase is the final electron transfer step, it receives

electrons from cytochrome c then passes them to oxygen to generate water. In addition 4 protons are pumped into the inter membranous space to enhance the proton gradient

Oxygen is an ideal

as it has a high affinity for electrons



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