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Question #46332
The Question
A patient exhibits severe acidemia due to impaired carbaminohemoglobin formation, leading to systemic CO2 accumulation. The kidneys attempt to compensate by maximizing H+ secretion. If a nephrotoxin simultaneously abolishes the counter-current multiplier mechanism, which of the following best explains why the renal compensation for acidosis will ultimately fail?
Options
- A.
The loss of medullary hypertonicity prevents adequate water reabsorption in the collecting duct, disrupting the luminal concentration gradient required for effective distal H+ secretion.
- B.
The absence of the NaCl gradient directly inhibits carbonic anhydrase in the proximal convoluted tubule, halting HCO3- regeneration.
- C.
Active secretion of H+ in the descending limb of the loop of Henle ceases because it is strictly coupled to the counter-current flow.
- D.
Obligatory water reabsorption in the proximal convoluted tubule is halted, diluting the filtrate and preventing the excretion of ammonia.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Hemoglobin-CO2 Binding Sites|Counter-Current Mechanism Multiplier|Micturition Reflex Control
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students typically compartmentalize the Counter-Current Mechanism strictly for water conservation (urine concentration) and PCT/DCT strictly for acid-base balance.
This question forces the synthesis of both concepts, highlighting that distal H+ secretion relies on the luminal concentration gradients and flow rates established by upstream water reabsorption, which is entirely dependent on medullary hypertonicity.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Breathing and Exchange of Gases - Class 11 |
| Concept | Hemoglobin-CO2 Binding Sites |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |