Before You Begin
Question #46313
The Question
A patient suffering from severe emphysema exhibits chronic hypercapnia, leading to respiratory acidosis. To compensate, the kidneys maximize the reabsorption of HCO3-. However, beyond a certain plasma concentration, HCO3- begins to appear in the urine, accelerating the drop in blood pH. Which of the following statements INCORRECTLY describes the physiological mechanisms involved in this scenario?
Options
- A.
The initial hypercapnia accelerates the chloride shift in systemic capillaries, increasing HCO3- generation via carbonic anhydrase.
- B.
The appearance of HCO3- in the urine indicates that its concentration in the glomerular filtrate has exceeded the maximum reabsorptive capacity of the PCT.
- C.
To compensate for the falling blood pH, the tubular cells of the DCT actively secrete HCO3- into the filtrate to neutralize the excess H+.
- D.
The inability of the kidneys to reabsorb the excess filtered HCO3- leads to a loss of blood buffering capacity, exacerbating the systemic acidosis.
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
Carbonic_Anhydrase|Chloride_Shift|Renal_Threshold_Concept
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between tubular secretion and tubular reabsorption in the context of acid-base balance.
Common Misconception: Students often assume that because the highly acidic urine needs buffering, the tubules secrete HCO3- into the lumen.
In reality, according to NCERT, the tubules secrete NH3 to buffer urine, while HCO3- is strictly reabsorbed to maintain the blood's pH.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Breathing and Exchange of Gases - Class 11 |
| Concept | Chloride Shift (Hamburger Phenomenon) |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |