When the blood becomes acidic (acidosis) and bicarbonate ions have been depleted, new bicarbonate ions must be generated in the plasma. Which of the following is NOT a means for replenishing bicarbonate ions?

a. Bicarbonate ions are reclaimed by tubular reabsorption.
b. Ammonium ions are excreted in urine.
c. Glutamine is metabolized by deamination, oxidation, and acidification.
d. Buffered hydrogen ions are excreted in urine.

c. Glutamine is metabolized by deamination, oxidation, and acidification.

Explanation:

Bicarbonate ions are an important part of bicarbonate buffer system which helps to maintain the pH of blood. Whenever blood starts to become acidic, bicarbonate ions increase to neutralize its effect. Their concentration can be increased by many mechanisms, for example tubular reabsorption.

However, glutamine catabolism does not replenish bicarbonate ions, in fact it does the exact opposite. Kidney generates ammonium ions by catabolism of glutamine which are excreted in the urine. This process also facilitates the excretion of bicarbonate ions.