Question

Explain the Proton-Motive force across the Inner mitochondrial membrane that both generates the H= gradient and aids In pulling H+ back Into the mitochondria matrix

Answer 1

Electron transport chain during the process of cellular respiration takes place in inner mitochondrial membrane. It begins with the donation of electrons by high energy electron carriers, NADH and FADH2 which are formed in the process of glycolysis, pyruvate oxidation and citric acid cycle. The electrons from NADH are donated to first Complex of electron transport chain, NADH reductase, and the elctrons from FADH2 are donated to ubiquinone which is the second Complex. The ubiquinone gets reduced to ubiquinol and than passes that two electrons to the third complex, cytochrome reductase. Then the electrons are passed on to cytochrome C which is IV Complex and then finally to cytochrome oxidase which is the last Complex. All these electron Carriers are arranged in increasing order of their electrochemical potential in the inner mitochondrial membrane. The electrons are released by the carrier having low affinity for electrons to the carrier having higher affinity for the electrons. Finally the electrons are accepted by oxygen which gets reduced to form water.

When electrons are carried from one electron carrier to the other, protons are also pumped from mitochondrial Matrix to intermembrane space. This results in the accumulation of protons in intermembrane space and results in the formation of proton gradient across inner mitochondrial membrane. The electrochemical energy stored in Proton gradient is utilised by ATP synthase enzyme for the synthesis of ATP by phosphorylation of ADP.

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