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Most chemical reactions are affected by the acidity of the solution in which they occur. As such, you can maintain a constant concentration of hydrogen ions within the physiological range, manipulate a particular reaction to occur or to proceed at an appropriate rate by controlling the pH of the reaction medium through the use of the appropriate biological buffer system.
Upon the addition of a strong base such as NaOH to the buffer solution, the hydrogen ion will bind with the hydroxide ion to form water. Upon the addition of a strong acid, however, the conjugate base will simply bind with the additional hydrogen ions to form acetic acid. In each case, equilibrium can be maintained.
Note: Weak acids and bases do not dissociate completely in water but exist in solution as a mixture of dissociated and dissociated molecules.
How Do Buffers Work?
All buffers have an optimal pH range over which they can moderate the changes in hydrogen ion concentration. This is generally defined as the pKa or the negative log of the dissociation constant of the acid. The pKa can be determined by using the Henderson-Hasselbalch equation:
pH = pKa + log10 [A-]/[HA]
However, since there are acids that can lose more than one hydrogen ion (polyprotic acids), they can have multiple pKa values. If the pKa values are close together, the optimal pH range will be a continuum determined by the range of pKas.
