Electrons, and Protons in Cell Membranes

FIGURE 2. The vectorial pumping of calcium ions and protons across the mitochondrion membranes. A schematic enlargement of the inner (cristae) membrane is shown to indicate the existence of protein-based electron (e) and proton (H + ) conduction pathways. On average, the cristae membrane is composed of 75 % protein and 25 % lipid. 

10 Vm acting across the membrane, with the outside of the cell at the more positive potential. It should be noted that Eq. (1) does not take account of the loss of free energy due to leakages of ions back across the membrane. In excitable tissues such as nerves, electrical impulses are produced as a result of the sudden increase in back-leakage of sodium and potassium ions, which causes a transient collapse of the transmembrane potential gradient. Some of the physical aspects associated with the membrane potential and associated diffuse electrical double layer, together with the active and passive transport of ions, will be discussed in this article. 

Since the introduction of the so-called chemiosmotic hypothesis by Mitchell, extensive experimental data obtained from mitochondria. 

On the other hand, concurrent with Mitchell s scheme has been that initiated by Williams, in which the following is envisaged  

FIGURE 3. Schematic representations of a bacterial cytoplasmic membrane to show the essential difference between (a) the bulk chemiosmotic, and (b) the local electrodic mechanism currently under active discussion as possible mechanisms by which the electron transport chain (e.t.c.) and ATP synthesis are coupled to vectorial proton translocation. (Based on Kell and Hitchens. 

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