protonbuffering

Protonbuffering is the ability of a chemical or biological system to resist changes in proton concentration, and thus pH, when exposed to acids or bases. In chemistry and biochemistry, protonbuffering is achieved by buffer systems that can donate or accept protons within a specific pH range. Common biological buffers include bicarbonate/carbon dioxide, phosphate, and various intracellular buffers such as titratable groups on proteins. Each buffer has a characteristic pKa, and maximal buffering capacity occurs near that pKa.

In living systems, protonbuffering operates at multiple levels. Intracellular buffering uses amino and carboxyl groups on proteins and other macromolecules to stabilize cytosolic and organellar pH. Extracellular buffering relies on soluble systems like bicarbonate in blood, which works in concert with respiratory CO2 regulation. Proton pumps, exchangers, and vesicular traffic also modulate proton distribution across membranes, helping to dampen pH excursions in compartments such as mitochondria and lysosomes.

The effectiveness of protonbuffering depends on the total amount of buffering agents and their distribution, as well as the proximity of the operating pH to the buffers' pKa values. In physiology, the concept is central to acid–base homeostasis, where buffering is complemented by respiratory and renal adjustments to maintain near-constant pH. The Henderson–Hasselbalch equation is commonly used to estimate pH and buffer ratios in practical contexts, alongside the notion of buffer capacity, which describes how much strong acid or base a system can absorb per unit change in pH.

Applications include designing laboratory buffers for biochemical assays, maintaining pH in cell culture, and understanding clinical acid–base disorders. See also acid–base balance, buffer solution, Henderson–Hasselbalch, and pKa.