Carbonic acid

A weak acid formed when carbon dioxide dissolves in water, including blood. When CO₂ falls, less carbonic acid and fewer hydrogen ions are present, so blood pH rises. The conversion between CO₂ and carbonic acid is sped up by an enzyme called carbonic anhydrase, so it happens within moments. Together with bicarbonate it forms the body's main buffer system for keeping blood pH stable. This is the chemical link between how we breathe and how acidic or alkaline our blood becomes.