Asked by | 5th Jan, 2009, 04:09: PM
The chemiosmotic hypothesis was proposed by Peter Mitchell. This hypothesis stated that a proton-motive force was responsible for driving the synthesis of ATP. In this hypothesis, protons would be pumped across the inner mitochondrial membrane as electrons went through the electron transfer chain. This would result in a proton gradient with an lower pH in the intermembrane space and a elevated pH in the matrix of the mitochondria. An intact inner mitochondrial membrane, impermeable to protons, is a requirement of such a model. The proton gradient and membrane potential are the proton-motive force that is used to drive ATP synthesis. In effect, the pH gradient acts as a "battery" which stores energy to produce ATP. Over the past several years, Mitchell's chemiosmotic hypothesis has been widely accepted as the mechanism of coupling of electron transport and ATP synthesis. He was awarded the Nobel Prize in Chemistry in 1978.
The electron transfer chains and the ATPases are asymmetrically oriented in the inner mitochondrial membrane. An asymmetric orientation is a requirement to establish a pH gradient. A random arrangement would not result in a net gradient of protons and therefore, no proton-motive force for the synthesis of ATP.
Electron transfer through the respiratory chain leads to the pumping of protons from the matrix to the cytosolic side of the inner mitochondrial membrane. The pH gradient and membrane potential constitute a proton-motive force that is used to drive ATP synthesis
Answered by | 5th Jan, 2009, 11:45: PM
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