Osmotic work

If the solution had been prepared by simply mixing solvent and solute in a calorimeter, without any performance of external osmotic work, the heat A would have been absorbed, where... 

Let us suppose the apparatus described in 188 is enclosed in a vessel into which an indifferent ga3 may be pumped, so that the whole system can be exposed to any total external pressure desired. If there is a change of total volume when solute passes into solution, it will give rise to the performance of work by, or against, the total pressure, quite independently of the osmotic work derivable from the apparatus inside. 

During ATP synthesis, protons move down these gradients from outside [Hour] into the mitochondrial matrix each proton doing both electrical and osmotic work (due to the concentration difference) so that the Gibbs energy change is... 

Osmotic Work. It is characteristic of living cells that they maintain nonequilibrium values of the concentrations of certain solutes on opposite sides of membranes, particularly ions such as Na and K. It is this nonequHibrium distribution of ions that probably is responsible for the electrical potentials developed by living organisms. Again, although thermodynamic data do not lead to deductions about molecular mechanisms, they provide limiting values with which any mechanism must be consistent. We shall discuss the thermodynamic aspects of osmotic work in detail when we have developed the methods requited to deal with solutions. 

The electrical work and osmotic work both performed in a perfectly reversible manner are equal, thus... 

Note also that, from a physicochemical point of view, in all schemes reflecting A/ZII-dependent transport systems on both sides of the membrane, H+ ions may be taken for a catalyst, which intensifies the proceeding of definite processes, either oxidative phosphorylation, osmotic work or other types of work. 

It is now eight decades since experimental evidence was obtained that mammalian cells are capable of extensive accumulation of amino acids (Van Slyke and Meyer, 1913). Shortly thereafter it became apparent that many other low molecular weight solutes were also accumulated in a variety of tissues. However, another 50 years were to pass before the mechanism of energy transduction between primary metabolic events and osmotic work was recognized and accepted. 

ATP has a ubiquitous and dominant role in cellular metabolism. This role can be appreciated more fully if cognizance is extended to the energy requirements of cells, to the regulation of cellular activity and metabolism imposed by ATP, and to what interference with ATP production means to the growth of a chloro-phyllous plant. Plants store oxidative and photochemical energy in the terminal phosphate bonds of ATP. The terminal bond energy is used subsequently to perform the chemical, mechanical, and osmotic work of the cell. 

Either the hydrolysis of ATP or the draining of an ion gradient is converted into an osmotic work by a pump or a mechanical work by a motor protein. Substrate binding sites in pumps or motor proteins occur in two sections (i) one of them binds the substrate and (ii) the other converges on the bound substrate molecule, and the protein changes into an... 

AjLtH when external energy sources are exhausted. The Na gradient is also used to perform osmotic work, i.e., the uphill uptake of metabolites by means of Na, metabolite-symporters. Halobacteria can also perform mechanical work (motility).It is not clear yet whether or Na -motors rotate the halobacterial flagella. 

The performance of a specific kind of osmotic work, namely, the uphill import of metabolites, represents yet another function of Ap. ... 

Equations (4) and (8) also apply to solutions of volatile substances. is then the partial pressure of the component, regarded as solvent, whose addition to the solution is accompanied by the doing of osmotic work. 

AVe can calculate the e.m.f. E of the combination, if we know the maximum work obtainable from the transference of 1 mol. of ZnSO from the concentrated to the dilute solution. (The work done against the atmospheric pressure owing to the change in volume of the solution may be neglected here.) It is sufficient for this purpose to calculate the work done when the transference is carried out reversibly. Helmholtz carried out this calculation for the isothermal distillation of the solvent from the dilute to the concentrated solution. Nern t calculated the osmotic work done in the process of dilution. 

We arrive at the same result by calculating the maximum osmotic work done in the dilution. In diluting 1 mol. of ZnSO. ... 

If we dealt with n gram-moles of solute the maximum osmotic work would be n times as great, viz —... 

Finally, at temperature T2, add the mass dx (which occupies the volume dV) of liquid solvent to the solution reversibly, the osmotic work being PdV This is the only nett work of the process The cycle is now completed For the sake of making the cycle clear all the steps have been described in detail For the puipose of using the... 

---