What does pKa measure?

pKa is a quantitative measure that reflects the strength of an acid in a solution. It is derived from the acid dissociation constant (Ka), which indicates how readily an acid donates protons (H+) to solution. A lower pKa value indicates a stronger acid, meaning it more fully dissociates into its ions at a given concentration, leading to a higher concentration of free protons in the solution. Conversely, a higher pKa indicates a weaker acid that doesn't dissociate as readily.

Understanding pKa is crucial in many biological systems because it affects the behavior of molecules in physiological conditions, including enzyme function and metabolic pathways. The acidity or basicity of a substance can impact cellular processes, binding interactions, and the stability of biomolecules, making pKa an essential concept in biochemistry.