MCAT Biology Question 70: Answer and Explanation
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Question: 70
10. Which of the following is FALSE regarding aldosterone regulation?
- A. Renin converts the plasma protein angiotensinogen to angiotensin I.
- B. Angiotensin II stimulates the adrenal cortex to secrete aldosterone.
- C. Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme.
- D. A decrease in blood oxygen concentrations stimulates renin production.
Correct Answer: D
Explanation:
The stimulus for renin production is low blood pressure, which causes the juxtaglomerular cells of the kidney to produce renin, an enzyme that converts the plasma protein angiotensinogen to angiotensin I. Angiotensin I is then converted to angiotensin II by an enzyme in the lungs; angiotensin II ultimately stimulates the adrenal cortex to secrete aldosterone. Aldosterone helps to restore blood volume by increasing sodium reabsorption in the kidney, leading to an increase in water reabsorption. This removes the initial stimulus for renin production. Thus, choices (A), (B), and (C) correctly describe the renin–angiotensin–aldosterone system, while choice (D) describes the stimulus for erythropoietin secretion.