Buffer systems maintian a constant pH in blood

The body maintains the pH of blood at around 7.4. If the pH level changes just a few tenths of a pH unit, serious health consequences can result. A decrease in blood ph is called acidosis, an increase is called alkalosis

Three different buffer systems exist in blood, the bicarbonate buffer and the phosphate buffer are composed of "simple" chemicals. In addition the carbonyl groups (-COOH) and the amide group (-NH2) present on proteins allow some of these to act as buffers. The bicarbonate buffer and the phospate buffer can be described by the following equilibria:

The pH for the bicarbonate buffer seems to be outside of its ideal range

Buffer capacity is usually defined as +/- 1 pH unit of the pKa. Notice that the pH of blood is is one unit away from the pKa of carbonic acid. Calculate the ratio of bicarbonate to carbonic acid implied by this. [Answer]

The ratio of bicarbonate to carbonic acid seems to be quite large (and in general this system would not be considered ideal for maintaining a pH of 7.4). However, physiologic conditions make this buffer ideal because:

In addition, the phosphate buffer as well as the buffering ability of proteins in plasma are also available to maintain blood pH.

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