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Q26 - Water Loading and Renal Handling in Two Groups of Students

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Homeostasis & Osmoregulation

Two groups of students separately performed an experiment on kidney function. Thirty minutes before the experiment, each student in one group was instructed to drink 500 mL of water, while each student in the other group was instructed to drink 100 mL of water. At t = 0 minute, each student in both groups was instructed to drink 750 mL of water. Each student was then asked to urinate as he or she would normally do without attempting to manipulate the speed or flow in any way at the different time points shown in Figure Q.26. An electronic uroflowmeter was used to measure the urine flow rate. The Cl- concentration in each urine sample was measured. Figure Q.26 shows the data of the experiment.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. The absolute reabsorption of water by nephrons of the students in Group II at t = 60 min was lower than that of the students in Group I.
B. The plasma aldosterone concentration of the students in Group I was the highest at t = 60 min.
C. The students in Group I drank 500 mL of water 30 minutes before the experiment.
D. The students in Group II produced about 140 mL of urine during the period between t = 40 min and t = 60 min.
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Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)