https://en.m.wikipedia.org/wiki/Acid–base_homeostasis

https://en.m.wikipedia.org/wiki/Chemical_equilibrium

Acid-Base Homeostasis

Outside the acceptable range of pH, proteins are denatured (i.e. their 3-D structure is disrupted), causing enzymes and ion channels (among others) to malfunction.

Many extracellular proteins such as the plasma proteins and membrane proteins of the body's cells are very sensitive for their three dimensional structures to the extracellular pH.[3][4] Stringent mechanisms therefore exist to maintain the pH within very narrow limits. Outside the acceptable range of pH, proteins are denatured (i.e. their 3-D structure is disrupted), causing enzymes and ion channels (among others) to malfunction.

In humans and many other animals, acid–base homeostasis is maintained by multiple mechanisms involved in three lines of defense:[5][6]

1. Chemical: The first lines of defense are immediate – the various chemical buffers which minimize pH changes that would otherwise occur in their absence. These buffers include the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system.[7]2. Respiratory Component: The second line of defense of the extracellular fluid pH is rapid, measured by PCO2, and consists of controlling the carbonic acid concentration in the ECF by changing the rate and depth of breathing (i.e. by hyperventilation or hypoventilation). This blows off or retains carbon dioxide (and thus carbonic acid) in the blood plasma as required.[5][8]3. Metabolic Component: The third line of defense is slow, best measured by the Base Excess[9], and mostly depends on the renal system which can add or remove bicarbonate ions to or from the ECF.[5] The bicarbonate is derived from metabolic carbon dioxide which is enzymatically converted to carbonic acid in the renal tubular cells.[5][10][11] The carbonic acid spontaneously dissociates into hydrogen ions and bicarbonate ions.[5] When the pH in the ECF tends to fall (i.e. become more acidic) the hydrogen ions are excreted into the urine, while the bicarbonate ions are secreted into the blood plasma, causing the plasma pH to rise (correcting the initial fall).[12] The converse happens if the pH in the ECF tends to rise: the bicarbonate ions are then excreted into the urine and the hydrogen ions into the blood plasma.

Chemical Equilibrium

Distribution between two phaseslog D distribution coefficient: important for pharmaceuticals where lipophilicity is a significant property of a drugLiquid–liquid extraction, Ion exchange, ChromatographySolubility productUptake and release of oxygen by hemoglobin in bloodAcid–base equilibria: acid dissociation constant, hydrolysis, buffer solutions, indicators, acid–base homeostasisMetal–ligand complexation: sequestering agents, chelation therapy, MRI contrast reagents, Schlenk equilibriumAdduct formation: host–guest chemistry, supramolecular chemistry, molecular recognition, dinitrogen tetroxideIn certain oscillating reactions, the approach to equilibrium is not asymptotically but in the form of a damped oscillation .[12]The related Nernst equation in electrochemistry gives the difference in electrode potential as a function of redox concentrations.When molecules on each side of the equilibrium are able to further react irreversibly in secondary reactions, the final product ratio is determined according to the Curtin–Hammett principle.