Chemiosmotic hypothesis (chemical osmotic hypothesis) Explain oxidative phosphorylation (see oxidative phosphorylation) mechanism hypothesis, proposed in 1961 by the British biochemist Mitchell (p.mitchell). He believes that the electron transport chain as a proton pump, the energy released during electron transfer, and can contribute to the proton shift from the mitochondrial matrix to form a space between the mitochondrial outer membrane proton electrochemical gradient that mitochondria h + concentration is greater than the outside and inside reserves of energy. When the electron transfer is pumped out of the protons in the h + concentration gradient driven by f0f1atp enzyme specific for h + channel or "tunnel" current return mitochondrial matrix, since h + current return freely released to provide f0f1atp enzymatic adp and pi conjugated generate atp. This hypothesis assumes that electron transfer driven, h + loop out into the mitochondria, while generating atp, although many of the properties can explain the process of oxidative phosphorylation, but there are still many issues not fully clarified.
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Chemiosmotic hypothesis
化学渗透假说
化学渗透假说
化学渗透假说
Outline Chemiosmotic hypothesis (chemical osmotic hypothesis) is explained oxidative phosphorylation (see oxidative phosphorylation) hypothesis mechanism, in 1961 by the British biochemist Mitchell (P.Mitchell) proposed. He believes that the electron transport chain as a proton pump, the energy released during electron transfer, and can contribute to the proton shift from the mitochondrial matrix to form a space between the mitochondrial outer membrane proton electrochemical gradient that mitochondrial H + concentration is greater than the outside and inside reserves of energy. When the electron transfer is pumped out of the proton of the H + concentration gradient driven by F0F1ATP enzyme specific H + in the channel or "tunnel" current return mitochondrial matrix, since H + current return freely released to provide F0F1ATP enzymatic ADP and Pi coupled to generate ATP. This hypothesis assumes that electron transfer driven, H + loop out into the mitochondria, while generating ATP, although many of the properties can explain the process of oxidative phosphorylation, but there are still many issues not fully clarified. Points A respiratory mediator asymmetrically distributed in the mitochondrial respiratory chain delivery of the hydrogen-donor and the electron mediator on the mitochondrial membrane has a specific asymmetric distribution, arranged alternately with each other, directional transmission. Two respiratory chain complexes with a hydrogen donor in the delivery of a proton pump effect. It can be from the inner mitochondrial membrane H + pump inside to the outside. In general an electron transfer from NADH to O2, the pump 6 of H +. FADH2 from the start of the pump 4 H +. The outer membrane H +, can not be returned freely through the inside of the intima, so that the electron transfer process, both sides of the proton concentration gradient established intimal (△ pH) and membrane electrical potential difference (△ E), which constitute the transmembrane H + electrochemical potential gradient △ μH +, If △ μH + changed to electric potential V as a unit, as compared to proton motive force. Proton concentration gradient is larger, the greater the proton motive force, the ability to synthesize ATP for the stronger. 3 by the proton motive force to promote the synthesis of ATP. So that H + proton motive flow freely along the ATP enzyme coupling factor when the H + channel into the mitochondrial matrix, the release of ADP and Pi can promote the synthesis of ATP. Chemical penetration theory has been ample experimental evidence. When mitochondria were suspended in buffer solution without O2, ventilation of O2, acidified medium quickly, the H + concentration difference across the membrane can be achieved 1.5pH unit, the potential difference of 0.5V, the outer face of the inner surface of the endometrium is positive, and remained relatively stable, proven endometrial endometrial allowed to H + leak back inside the outside. But when adding uncoupler 2,4 dinitrophenol (DNP), the H + concentration difference transmembrane potential difference and can not be formed, it will prevent the generation of ATP. Some people Halophile purple membrane proteins and mitochondrial ATPase embedded liposomes, suspended in a solution containing ADP and Pi, in the light under the purple membrane protein intake H + from the medium, resulting in transmembrane H + concentration difference, pushing the ATP synthesis. When artificial endometrium establish appropriate cross the H + concentration is poor, also found that ADP and Pi synthesis of ATP. Despite the large number of experimental evidence to support the theory of chemical penetration, but the molecular mechanism of ATP synthesis so far unclear. The hypothesis of the features: 1, emphasizing the integrity of the mitochondrial membrane If the film is not complete, H + can freely through the mitochondrial membrane, the membrane can not be formed on both sides of proton motive force, the uncoupling of oxidative phosphorylation will; (this mechanism is the number of uncoupler, altered mitochondrial membrane permeability of H + , and is the release of electron transfer Energy can not be used to put synthetic ATP) 2, the orientation of the chemical reaction ATP hydrolysis reaction is directional, H + from the mitochondrial membrane matrix extracted into the gap, resulting in an electrochemical proton gradient. ATP synthesis reaction is also directed, in an electrochemical proton gradient driven, H + clearance by the membrane, the membrane through ATP synthase, into the mitochondrial matrix, promote the energy ADP and Pi - ATP. 3, power ATP synthesis: the proton motive force, each into two H +-driven synthesis of an ATP; 4, electron transport and ATP synthesis are two related but different events
