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Question #46396
The Question
A patient with uncontrolled diabetes mellitus presents with severe polyuria and systemic dehydration. Laboratory tests reveal high titers of circulating ADH (Vasopressin). Which of the following statements correctly explains why the kidneys fail to concentrate urine despite the presence of ADH?
Options
- A.
Unabsorbed glucose increases the luminal osmolarity of the filtrate, which counteracts the medullary osmotic gradient and prevents water efflux from the collecting duct.
- B.
Excess glucose in the filtrate actively diffuses into the medullary interstitium, washing out the concentration gradient maintained by NaCl and urea.
- C.
The saturation of carrier proteins in the proximal convoluted tubule triggers a reflex inhibition of aquaporin insertion in the distal convoluted tubule.
- D.
High tubular flow rate due to glucosuria prevents the active transport of electrolytes in the descending limb of the loop of Henle.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
PCT Selectivity|Glucose|Renal Threshold
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume the mere presence of ADH guarantees water reabsorption.
The misconception is ignoring the driving force for osmosis.
ADH only provides the pathway (aquaporins); the actual movement of water strictly requires a favorable osmotic gradient, which is counteracted by the high luminal osmolarity of unabsorbed glucose.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Nitrogenous Waste Classification |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |