Advanced Placement (AP) Chemistry Practice Exam

Which statement accurately reflects the role of buffers in biological systems?

1. Buffers isolate reactions from environmental influences.

2. Buffers maintain a constant pH despite the addition of acids or bases.

3. Buffers are always composed of strong acids or strong bases.

4. Buffers can only function in neutral pH environments.

The correct answer is: Buffers maintain a constant pH despite the addition of acids or bases.

Buffers play a crucial role in maintaining a stable pH in biological systems, which is vital for the proper functioning of enzymes and biochemical reactions. The correct statement is that buffers maintain a constant pH despite the addition of acids or bases. They typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid, allowing them to neutralize small amounts of added acids or bases without a significant change in pH. In biological contexts, such as human blood or cellular environments, the ability to resist changes in pH is essential because many physiological processes are pH-sensitive. If significant pH fluctuations occur, it can lead to detrimental effects on cellular functions and overall metabolic processes. The other statements do not accurately reflect the nature and function of buffers. Buffers do not isolate reactions from environmental influences; instead, they interact with those influences to stabilize pH. Additionally, buffers are not composed of strong acids or bases, as strong acids and bases completely dissociate in solution, failing to provide the necessary control to stabilize pH. Finally, buffers are not limited to functioning only in neutral pH environments; they can effectively maintain stability in both acidic and alkaline conditions.