What is the primary role of a buffer in a biochemical reaction?

The primary role of a buffer in a biochemical reaction is to resist changes in pH when acids or bases are added. Buffers are solutions that contain a weak acid and its conjugate base (or vice versa); they function to maintain a stable pH in a solution even when small amounts of strong acids or bases are added. This is critical in biological systems where many enzymatic reactions are sensitive to pH changes. Stability of pH is essential for maintaining optimal conditions for biomolecules, including proteins and nucleic acids, to function properly.

In contrast, while factors like temperature and conductivity can influence biochemical reactions, they do not define the function of a buffer. Buffers do not increase temperature and are not designed to provide visual representations of reactions. Their key feature is maintaining pH balance rather than enhancing the solution's physical properties, which is why "to resist changes in pH" correctly captures the essence of a buffer's role in biochemical settings.