Salient features

This is a simpler, radically different, and novel mechanism and was postulated by Peter Mitchell, a British biochemist in 1961. He proposed that “electron transport and ATP synthesis are coupled to high-energy intermediate or an activated protein” as shown in Figure 8.23.

According to this model, the transfer of electrons through the respiratory chain results in the pumping of protons (H⁺) from the matrix side (M side) to the cytosol or cytoplasmic side (C-side) of inner mitochondrial membrane. The concentration of H⁺ becomes positive on the cytoplasmic side. The hypothesis further proposes that H⁺ ions ejected by electrons transport flow back into the matrix through a specific H⁺ channel or ‘pore’ in the F₀F₁ ATPase molecule, driven by the concentration gradient of H⁺. The free energy released as proton (H⁺) flows back through the ATPase and causes the coupled synthesis of ATP from ADP and phosphate by ATP synthetase.

Figure 8.23 Chemiosmotic Coupling Hypothesis