Which of the following substances is responsible for donating H+ ions to act as a buffer when blood pH rises?
A. Carbon monoxide
B. Carbonic acid
C. Carbon dioxide
D. Oxygen
The physiological function of the body depends on the balance between the concentrations of acids and bases in the blood. For a better body function, the blood pH falls in the range of 7.45 and 7.35. beyond this point, the blood my become too acidic or basic and may have drastic effect on the physiologic function of the body. To maintain this blood at constant, the buffer system comes into play. It does not allow the pH to drop or increase drastically. From the properties of acids and bases, acids donate protons while bases are proton acceptors. In our bodies, there are three buffer systems:
- Carbonate/carbonic acid buffer
- Phosphate buffer
- Plasma proteins
Th carbonate/carbonic acid buffer plays a key role in acid-base balance in our bodies. This buffer system is regulated by the respiratory system. If there is less H ions on the system, the carbonic acid dissociates and donate H ions as show in the reaction below, which thus declines the pH of the blood.
H2CO3 + H2O ? H3O+ + HCO3-
Therefore, the Correct Answer is B.