Question

a) In terms of the electron transport chain, what is a “coupling site”?

b) Using redox calculations, prove that there are three coupling sites in the electron transport chain in mitochondria. This means that for each reaction, you should write out the balanced redox equation for the reaction, calculate the ΔE⁰, and calculate the ΔG⁰.

Answer 1

a) Coupling site:

The linking of two independent processes by a common intermediate is called as coupling,for example the coupling of electron transport to oxidative phosphorylation or the ATP and ADP conversion to transport processes.The place or the site where the coupling reaction takes place is the coupling site.

b) There are three coupling sites in the electron transport chain in mitochondria since the electron transport chain occurs by using the three major enzyme complexes of the respiratory chain ubiquinone and cytochrome c diffuse rapidly in the plane of the inner mitochondrial membrane.There are three coupling sites in a ETC in mitochondria.

where is the Gibbs free energy

n is the number of electrons

F is the Faraday constant

is the reduction potential