Skill 21.5 Recognizing the importance and role of buffers in biological systems

Skill 21.5 Recognizing the importance and role of buffers in biological systems. 

Buffers are substances that cause the solution in which they are present to resist changes in pH. A buffer agent is either a weak acid or a weak base, and, when in an aqueous state, the buffer agent forms a buffer solution. Since many biological processes require highly specific pH levels, buffers are critical to sustaining life in organisms. 

Enzymes, which are reaction catalysts that are crucial components of biochemical processes, can only perform their functions efficiently when their environment is within a certain pH range. Most enzymes display a so-called pH optimum for which enzyme activity is maximized. Variations in pH can cause enzyme activity to slow or cease, and extreme variations in pH can cause enzymes to become denatured. In non-buffered solutions, the addition of small amounts of basic or acidic substances can cause significant changes in pH. 

Since biological systems are dynamic, with many different processes taking place and many different substances present, buffers are necessary to prevent the kind of wide variation of pH that can inhibit proper enzyme catalysis. Thus, a proper pH aids in regulating the reaction rates associated with certain enzymes and maintaining them at levels appropriate for their particular functions. Two important biological buffers are the phosphate buffer system that regulates pH for the fluid inside cells and the carbonic acid buffer system that regulates pH for blood plasma. The chemical equations for these buffers are shown below for an aqueous solution. 

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