MCAT Biology Question 147: Answer and Explanation
Home > MCAT Test > MCAT biology practice tests
Test Information
- Use your browser's back button to return to your test results.
- Do more MCAT biology practice tests.
Question: 147
12. When the pH of the blood is high, which substance is likely to be excreted in larger quantities in the urine?
- A. Urea
- B. Ammonia
- C. Hydrogen ions
- D. Bicarbonate ions
Correct Answer: D
Explanation:
When the pH of the blood is high, this indicates that the blood is alkalemic. In order to correct the pH of the blood, the kidney will increase the excretion of a base, namely bicarbonate. Excretion of urea would have little effect on the pH, eliminating choice (A). While ammonia is a base, it is quite toxic and is generally converted to urea before excretion, eliminating choice (B). Excretion of hydrogen ions would result in exacerbation of the alkalemia, eliminating choice (C).