Introduction to Apparent Equilibrium Constants

2006 ◽  
pp. 29-42
Keyword(s):  
Equilibrium Constants ◽  
Apparent Equilibrium

scholarly journals Adjustment of K' to varying pH and pMg for the creatine kinase, adenylate kinase and ATP hydrolysis equilibria permitting quantitative bioenergetic assessment.

1995 ◽  
Vol 198 (8) ◽  
pp. 1775-1782 ◽  
Author(s):  
E M Golding ◽  
W E Teague ◽  
G P Dobson
Keyword(s):  
Creatine Kinase ◽  
Gibbs Energy ◽  
Adenylate Kinase ◽  
Atp Hydrolysis ◽  
Equilibrium Constants ◽  
Binding Constants ◽  
Acid Dissociation ◽  
Free Magnesium ◽  
Apparent Equilibrium ◽  
Energy Of Formation

Physiologists and biochemists frequently ignore the importance of adjusting equilibrium constants to the ionic conditions of the cell prior to calculating a number of bioenergetic and kinetic parameters. The present study examines the effect of pH and free magnesium levels (free [Mg2+]) on the apparent equilibrium constants (K') of creatine kinase (ATP: creatine N-phosphotransferase; EC 2.7.3.2), adenylate kinase (ATP:AMP phosphotransferase; EC 2.7.4.3) and adenosinetriphosphatase (ATP phosphohydrolase; EC 3.6.1.3) reactions. We show how K' can be calculated using the equilibrium constant of a specified chemical reaction (Kref) and the appropriate acid-dissociation and Mg(2+)-binding constants at an ionic strength (I) of 0.25 mol l-1 and 38 degrees C. Substituting the experimentally determined intracellular pH and free [Mg2+] into the equation containing a known Kref and two variables, pH and free [Mg2+], enables K' to be calculated at the experimental ionic conditions. Knowledge of K' permits calculation of cytosolic phosphorylation ratio ([ATP]/[ADP][Pi]), cytosolic free [ADP], free [AMP], standard transformed Gibbs energy of formation (delta fG' degrees ATP) and the transformed Gibbs energy of the system (delta fG' ATP) for the biological system. Such information is vital for the quantification of organ and tissue bioenergetics under physiological and pathophysiological conditions.

scholarly journals Single-Route Linear Catalytic Mechanism: A New, Kinetico-Thermodynamic Form of the Complex Reaction Rate

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1748 ◽  
Author(s):  
Gregory S. Yablonsky ◽  
Denis Constales ◽  
Guy B. Marin
Keyword(s):  
Reaction Rate ◽  
Catalytic Mechanism ◽  
Equilibrium Constants ◽  
Complex Reaction ◽  
Thermodynamic Factor ◽  
Kinetic And Thermodynamic Parameters ◽  
Kinetic Factor ◽  
Buffer Substance ◽  
Apparent Equilibrium ◽  
Thermodynamic Factors

For a complex catalytic reaction with a single-route linear mechanism, a new, kinetico-thermodynamic form of the steady-state reaction rate is obtained, and we show how its symmetries in terms of the kinetic and thermodynamic parameters allow better discerning their influence on the result. Its reciprocal is equal to the sum of n terms (n is the number of complex reaction steps), each of which is the product of a kinetic factor multiplied by a thermodynamic factor. The kinetic factor is the reciprocal apparent kinetic coefficient of the i-th step. The thermodynamic factor is a function of the apparent equilibrium constants of the i-th equilibrium subsystem, which includes the (n−1) other steps. This kinetico-thermodynamic form separates the kinetic and thermodynamic factors. The result is extended to the case of a buffer substance. It is promising for distinguishing the influence of kinetic and thermodynamic factors in the complex reaction rate. The developed theory is illustrated by examples taken from heterogeneous catalysis.

Design of Acidic Ni-Mo Alloy Plating Baths Using a Set of Apparent Equilibrium Constants

2004 ◽  
Vol 151 (12) ◽  
pp. C798 ◽  
Author(s):  
Kuniaki Murase ◽  
Mitsuyasu Ogawa ◽  
Tetsuji Hirato ◽  
Yasuhiro Awakura
Keyword(s):  
Equilibrium Constants ◽  
Alloy Plating ◽  
Apparent Equilibrium

scholarly journals Invariance of apparent equilibrium constants with pH1

1974 ◽  
Vol 19 (4) ◽  
pp. 665-669 ◽  
Author(s):  
R. M. Pytkowicz ◽  
S. E. Ingle ◽  
C. Mehrbach
Keyword(s):  
Equilibrium Constants ◽  
Apparent Equilibrium

Calcium binding by lithocholic acid derivatives

1984 ◽  
Vol 247 (1) ◽  
pp. G112-G115
Author(s):  
D. G. Oelberg ◽  
W. P. Dubinsky ◽  
E. W. Adcock ◽  
R. Lester
Keyword(s):  
Calcium Binding ◽  
Bile Salts ◽  
Lithocholic Acid ◽  
Equilibrium Constants ◽  
Taurocholic Acid ◽  
Selective Electrode ◽  
Acid Sulfate ◽  
Ion Concentrations ◽  
Glycocholic Acid ◽  
Apparent Equilibrium

Lithocholic acid (LCA) and its sulfate (LCS) and glucuronide (LCG) derivatives are potent cholestatic agents. During the course of LCG-induced cholestasis in rats, calcium (Ca) salts of LCG precipitate in bile. To characterize the affinity of bile salts for Ca, solutions of selected bile salts were titrated with Ca. Apparent equilibrium constants (KcaBS) were determined from the unbound Ca ion concentrations that were measured spectrophotometrically with metallochromic indicators antipyrylazo III or murexide or with a Ca-selective electrode. KCaBS values were 1.12 +/- 0.04 X 10(-4) M for LCS, 2.88 +/- 0.26 X 10(-4) M for LCG, 3.09 +/- 0.21 X 10(-4) M for LCA, 1.93 +/- 0.07 X 10(-3) M for taurocholic acid (TC), 2.69 +/- 0.08 X 10(-3) M for glycocholic acid (GC), and 6.07 +/- 0.27 X 10(-3) M for taurolithocholic acid sulfate (TLCS). The KCaBS for LCG measured by a Ca-selective electrode under identical conditions was 5.53 +/- 2.75 X 10(-4) M. Comparing relative cholestatic potential with affinity for Ca, cholestatic bile salts LCS, LCG, and LCA bind Ca 10-60 times more avidly than TC, GC, and TLCS. At the unbound Ca ion concentrations of serum or bile (approx 1 mM), only LCS, LCG, and LCA would be expected to bind significant amounts of Ca.

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