Flow-force relationships

Isolation of Cells for Transport Studies Use of nonequilibrium thermodynamics in the analysis of transport general flow-force relationships and the linear domain, 171, 397 cell isolation techniques use of enzymes and chelators, 171, 444 cell separation by gradient centrifugation methods, 171, 462 cell separation by elutriation major and minor cell types from complex tissues,... 

Michaelis-Menten equation shows that the enzyme reactions in certain regions can be approximated by linear kinetics. Stucki (1984) demonstrated that variation of the phosphate potential at constant oxidation potential yields linear flow-force relationships in the mitochondria. Through linear flow-force relationships, cells may optimize their free energy production and utilization by lowering their entropy production and hence exergy losses at stationary states. 

The quasi-linear variation of power with ATP hydrolysis is observed experimentally, as the contraction is being activated at the level of actinomyocin activity. The kinetic approach suggests that the muscle power output varies hyperbolically with the ADP concentration. Both the ADP control and the Gibbs energy of ATP hydrolysis control are similar, and when muscle power is varied voluntarily, muscle energetics may be represented by the linear flow-force relationships. 

Essig and Caplan [15] have made the point that, since a priori the physical constraint is arbitrary, it may be chosen such that v varies linearly with /is-/tp. After having shown that linear flow-force relationships may have great advantages for biological systems. Stuck [16] suggested that the latter may have evolved in such a manner that linearity resulted. Below we shall examine the case in which classical... 

Only for certain kinetic constants, and sum concentration of substrate plus product, Pg = Pp and AG become zero, so that the flow-force relationship of Eqn. 20 which was used in near-equilibrium non-equilibrium thermodynamics [1,3-5,8], becomes valid. It should be noted that only at low magnitudes of [S] -I- [P] does the condition AG = 0 coincide with = 1. 

Many theoretical and empirical questions remain, pertaining to the thermodynamics (as well as the kinetics) of metabolic processes in organized states. Nevertheless, there is an ominous shadow of doubt on much of our current quantitative knowledge of flow-force relationships for biochemical reactions in the living cell (Welch, 1985b). 

The terms Lh, Lq, and Lp are the transport coefficients for proton, oxygen, and ATP flows, respectively. The Y factors describe the enzyme-catalyzed reactions with the rates having different sensitivities in the change of free-energy for the proton pump and other reactions. This differential sensitivity is a characteristic of the enzyme and is reflected hy the mosaic nonequilihrium thermodynamics formulation of the flow-force relationships of that enzyme. The term h shows the number of protons translocated per ATP hydrolyzed, while 7h> o> and Jp indicate the flows of hydrogen, oxygen, and ATP, respectively. 

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