39. Which of the following substances is responsible for donating H+ ions to act as a buffer when blood pH rises?
Answer: D
Carbonic Acid is responsible for donating H+ ions to act as a buffer when blood pH rises.
When blood pH rises, carbonic acid donates H+ ions to help stabilize the pH level, acting as a key buffer in the blood.
A) Carbon Monoxide
Carbon monoxide is a colorless, odorless gas that primarily affects oxygen transport in the blood by binding to hemoglobin. It does not participate in acid-base balance or donate H+ ions, making it an incorrect option for buffering blood pH.
B) Oxygen
Oxygen is essential for cellular respiration and energy production but does not play a role in buffering blood pH. It does not donate H+ ions, thus making it an unsuitable choice in the context of acid-base equilibrium.
C) Carbon Dioxide
Carbon dioxide is involved in the regulation of blood pH through its conversion to carbonic acid; however, it does not directly donate H+ ions. Instead, it is a precursor in the buffering system rather than the active buffering agent, rendering it an incorrect answer.
D) Carbonic Acid
Carbonic acid is crucial for regulating blood pH as it can release H+ ions when the pH rises, thereby helping to maintain acid-base balance. This property makes it the correct answer as it directly contributes to buffering excess alkalinity in the blood.
Conclusion
Carbonic acid effectively donates H+ ions when blood pH increases, making it a vital component of the buffering system in the body. The other options do not fulfill this role: carbon monoxide and oxygen do not participate in acid-base regulation, while carbon dioxide serves as a precursor rather than an active buffer. Thus, carbonic acid stands out as the definitive correct answer.