Osmotic theory

The chemi-osmotic theory of oxidative phosphorylation has been reviewed,74 a model for mitochondrial oxidative phosphorylation in which a membrane potential or proton gradient might transmit energy from an oxidation step to ATP synthesis has been proposed,76 and adenine nucleotide transport in mitochondria has been reviewed.76... 

A different direction in ion-selective electrode research is based on experiments with antibiotics that uncouple oxidative phosphorylation in mitochondria [59]. These substances act as ion carriers (ionophores) and produce ion-specific potentials at bilayer lipid membranes [72]. This function led Stefanac and Simon to obtain a new type of ion-selective electrode for alkali metal ions [92] and is also important in supporting the chemi-osmotic theory of oxidative phosphorylation [69]. The range of ionophores, in view of their selectivity for other ions, was broadened by new synthetic substances [1,61]. 

Peter Mitchell (Nobel Prize, 1978) of Great Britain was the first to realize, and to propose in his chemi-osmotic theory, that the energy required for die ADP-ATP reaction could be derived by an accretion of protons in the thylakoid sac to the point at which the electrochemical gradient across the membrane could effect the proton transport required as die driving force for this reaction. See also Phosphorylation (Photosynthetic). 

One more isotherm equation that could be helpful for the determination of the micropore volume is the osmotic isotherm of adsorption. Within the framework of the osmotic theory of adsorption, the adsorption process in a microporous adsorbent is regarded as the osmotic equilibrium between two solutions (vacancy plus molecules) of different concentrations. One of these solutions is generated in the micropores, and the other in the gas phase, and the function of the solvent is carried out by the vacancies that is, by vacuum [26], Subsequently, if we suppose that adsorption in a micropore system could be described as an osmotic process, where vacuum, that is, the vacancies are the solvent, and the adsorbed molecules the solute, it is possible then, by applying the methods of thermodynamics to the above described model, to obtain the so-called osmotic isotherm adsorption equation [55] ... 

In the late 1960s, the field ofbioenergetics and ATP synthesis was stimulated by Peter Mitchell s chemi-osmotic theory and, for which Mitchell was awarded the Nobel Prize in 1978. Currently, we have a similar situation, namely, the stimulation provided by Boyer s binding change theory of ATP synthesis. Capaldi has aptly described how the three-dimensional structure work probably had the effect of reenergizing thinking on the molecular mechanism of ATP synthesis. 

The general conclusion which has been come to, however, is that the Neinst method of treatment of e m f in cells represents a great advance m our knowledge of this important phenomenon One or two simple cases of the application of the osmotic theory will now be given... 

It is evident that the temperature coefficient of the cell is much less than that required by the simple osmotic theory It is only in the case... 

Electromotive Force of Concentration Cells —In the preceding chapter (Chap VII) it has been shown that the simple osmotic theory of the production of emf of a cell reversible with respect to the cation leads to the expression—... 

We thus see that it is possible to calculate the solution tension characteristic of each electrode (except for a constant factor) or the electrode potentials (except for an additive constant). In the practical application of the figures the constant naturally disappears since the electrode potential may be arbitrarily assumed for one electrode, e g. equated to zero for the hydrogen electrode. Now the osmotic theory allows the E.M.F. of any galvanic arrangement to be determined in which dilute aqueous solutions are employed we thus see that this theory is amplified by our thermodynamic treatment, in that the electrode potentials are now made accessible to simple theoretical calculations, instead of having to be determined for a given temperature, when using the osmotic theory, by means of measurements carried out on each of the electrodes in question for the electrode potentials are derivable from thermal data and solubilities. 

The use of the macro-d5uiamical method previously in connection with the osmotic theory of force [the diffusion of electrolytes and ionic mobilities by Nemst diffusion and the hydrodynamic (Stokes ) radius of molecules according to W. Sutherland and Einstein] is weU known. An alternative, simple formulation of two-component diffusion, Eq. (10), is possible if another form of the thermod5mamic factor, based upon osmotic pressme is applied ... 

D. J. F. Bowling, "Evidence for the Electro-osmotic Theory of Transport in the Phloem, Biochim. Biophys. Acta 183, 230-232 (1969). 

In the preceding section we have already met a theory on the mechanism of swelling of proteins in dependence of the hydrogen-ion concentration of the solution which may be termed the osmotic theory, and which seemed to be rather well supported... 

Ostwald resigned the professorship at Leipzig in 1905, after differences with the university authorities. During his period there he trained a large number of students, and directed the research of a number of workers, including British and American, who spread the new physical chemistry to all countries. The school was mainly based on Arrhenius s theory of electrolytic dissociation, van t Hoff s osmotic theory of solutions, and the applications to chemistry of the laws of thermodynamics. In 1909 Ostwald received the Nobel Prize for his work on catalysis. ... 

Many hypothesis have been emitted concerning the fate of the protons during this pH variation and its relationship with the osmotic theory of P. Mitchell (1979), but the molecular mechanism of this ATP synthesis remains unknown. 

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