In the biological system, the energy released by energy substances such as protein, fat and sugar in the oxidation phase is removed from the substrate by NAD and FAD in the form of high-energy electrons, which are carried by NADH and FADH2, and energy is transferred to O2 through the electrons in the respiratory chain on the inner membrane. The energy of electrons is released in the process of transmission and is used for proton H transmembrane pumping, that is, the proton from Mitochondrial matrix The reverse concentration is transported across the membrane to the inter membrane cavity, resulting in an electrochemical H gradient on both sides of the inner membrane. According to“ Chemical osmosis hypothesis ”When electrons are transferred along the respiratory chain, the released energy pumps protons from the matrix side of the intima (M side) to the membrane gap (cytoplasmic side or C side) Mitochondrial intima It is highly impermeable to ions, so that the proton concentration in the membrane gap is higher than that in the matrix, and the pH gradient (△ pH) and potential gradient (Ψ) are formed on both sides of the inner membrane Electrochemical gradient (Figure 7-12), namely proton dynamic potential (△ P). △P=Ψ-(2.3RT/F)△pH
Where T is the absolute temperature, R is the gas constant, and F is the Faraday constant. A large number of experiments show that when the temperature is 25 ℃, △ P=Ψ - 59 △ pH, and the value of △ P is about 220 mV.
