Possible mechanisms of the energy-dependent charge-specific ion transfer through the membranes of mitochondria, submitochondrial particles and bacterial chromatophores are considered.

It is concluded that penetrating ions move in the electric field orientated across energy-producing membranes and supported by electron and hydrogen transfer or ATP hydrolysis. The following three possibilities for the generation of membrane potential are discussed:

1.Both the respiratory chain and ATPase operate as H pumps thereby creating a potential difference across the membrane (Mitchell's scheme).

2.There exists a special pump driven by hydrolysis of a high-energy intermediate of oxidative phosphorylation.

3.Only the respiratory chain can directly produce the membrane potential, whereas ATP energy can be utilized for this purpose via reverse electron transfer.

In the first case, the function of the membrane potential should be the coupling of oxidation and phosphorylation. In the second and the third cases the membrane potential would be functioning as an ‘energy buffer’ and (or) as a mechanism for transport of penetrating compounds through the energy-producing membranes against concentration gradients.

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