Answer:
When blood is too basic, carbonic acid can ionize to bicarbonate and H+ ions, adding H+ ions to the blood.
When blood becomes too acidic, bicarbonate combines with extra H+ ions to form carbonic acid, removing H+ ions from the blood.
Carbonic acid can raise or lower the pH of blood.
Explanation:
A buffer is a solution that resists changes to its pH when small quantities of acids or bases are added to it. The human blood serves as a buffer as it contains a buffer of carbonic acid (H2CO3) and bicarbonate anion (HCO3-) which serves to maintain blood pH between 7.35 and 7.45. Other buffering systems in blood exist such as the Hydrogen ion and oxygen gas which affects oxygen binding to haemoglobin, however the carbonic-acid-bicarbonate buffer is the most important buffer for maintaining acid-base balance in the blood.
A buffer solution is made up of an acid and its conjugate base or a base and its conjugate acid. For carbonic acid-bicarbonate buffer, carbonic acid serves as the acid while bicarbonate serves as the base. When a little quantity of a base as hydroxide ions is added to a buffer, the acid reacts with it and remove it from the solution. On the other hand, when a little quantity of an acid as hydrogen ions are added to a buffer, the conjugate base reacts with it and remove it from the solution, thus keeping the pH of the solution fairly constant.
In the carbonic acid-bicarbonate buffer:
When blood is too basic, carbonic acid can ionize to bicarbonate and H+ ions, adding H+ ions to the blood.
When blood becomes too acidic, bicarbonate combines with extra H+ ions to form carbonic acid, removing H+ ions from the blood.
Thus, carbonic acid can raise or lower the pH of blood.
