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Question #45751
The Question
In anaerobic microbial ecosystems (like methanogen-rich sludge), metabolic shifts manage high organic acid loads. Similarly, during severe systemic metabolic acidosis in humans, the kidneys must maximize acid excretion to prevent the failure of pH homeostasis. Which of the following accurately describes the primary renal compensatory mechanism and its physiological limitation?
Options
- A.
Enhanced metabolism of glutamine in the Proximal Convoluted Tubule (PCT) to secrete NH3, limited by the saturation kinetics of tubular transport mechanisms.
- B.
Increased active secretion of H+ in the descending limb of the Loop of Henle, limited by the counter-current multiplier system.
- C.
Maximum reabsorption of filtered HCO3- in the Collecting Duct, limited by the availability of Anti-Diuretic Hormone (ADH).
- D.
Direct secretion of NH4+ into the Distal Convoluted Tubule (DCT) via passive diffusion, limited by the luminal pH.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Methanogens|Ammonia_Buffer_System|Metabolic_Acidosis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often know that the kidneys secrete H+ and NH3 to maintain pH, but frequently fail to pinpoint the exact location (PCT for glutamine-derived ammoniagenesis) and the nature of the transport limitation (saturation kinetics/Tm).
The trap relies on confusing the permeability of the Loop of Henle segments and the diffusion properties of NH3 versus NH4+.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Tubular Secretion Specificity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |