concept

Bicarbonate buffer

The mechanism that keeps blood acidity steady even though the body produces acid continuously. Carbon dioxide dissolved in water becomes carbonic acid, which immediately splits into a bicarbonate ion and a hydrogen ion - and hydrogen ions are what acidity is. Because the reaction runs both ways, a large standing pool of bicarbonate in the plasma absorbs incoming hydrogen ions and turns them back into carbon dioxide and water. It is an open buffer: the volatile product is vented continuously across the respiratory surface, which gives it far more capacity than a closed system would have.