A buffer solution is defined as a solution that effectively resists changes in pH.

Buffer solutions play a crucial role in biological systems by maintaining a stable pH, which is essential for numerous biochemical reactions. These solutions are typically composed of a weak acid along with its corresponding conjugate base, or alternatively, a weak base paired with its conjugate acid. When an acid or a base is introduced into a buffer solution, the components of the buffer engage in chemical reactions with the added substance, thereby preventing significant fluctuations in pH.

The ability of a buffer solution to resist changes in pH stems from the equilibrium established between the weak acid and its conjugate base. For instance, when an acid is added to the buffer, the weak base present in the solution reacts with the added acid to produce more of the weak acid. This reaction effectively neutralizes some of the added acid, thereby mitigating a substantial change in pH. Conversely, when a base is introduced, the weak acid component of the buffer reacts with the base to generate more of the weak base, similarly neutralizing some of the added base and preventing drastic changes in pH.

Buffer solutions are integral to many biological processes, such as in blood, where they help maintain a stable pH despite variations in metabolic activity. Additionally, these solutions are extensively used in laboratory settings to ensure that a constant pH is preserved during experiments.