Q72 - Identifying PTH, Calcium, and Phosphate Curves After PTH-Secretion Blockade
Parathyroid hormone (PTH) plays an important role in the regulation of plasma calcium and phosphate levels. Figure Q.72 shows the changes in levels of PTH, Ca2+, and phosphate (Pi) in plasma of mice injected with a specific inhibitor of PTH secretion, tracked as three curves (Line I, Line II, Line III) over time from before to after the point of injection.
Figure Q.72
Figure 1.
Using the information and data, determine which of the statements are true or which are false.
A. If Line I shows the level of PTH, then Line II and Line III would likely be showing the levels of Pi and Ca2+, respectively.
B. PTH knock-out mice would have higher Pi levels in their urine compared with the wild type mice on the same diet.
C. Eating a calcium-rich diet decreases the plasma level of vitamin D (active form) in healthy people.
D. People with calcium-sensing receptor suppression have higher levels of plasma Ca2+ compared with healthy people on the same diet.
Question reproduced from IBO 2016, Theoretical Paper B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)