Which of the following is false regarding the reabsorption of bicarbonate ion (HCO₃⁻)?

Correct Answer: C

Rationale: CO₂ combining with H₂O via extracellular carbonic anhydrase is false occurs intracellularly (e.g., PCT enzyme). H secretion and H₂CO₃ formation are true HCO₃⁻ reclaimed. Poor permeability holds indirect reabsorption. Intracellular site distinguishes the error, key to bicarbonate mechanism, unlike correct steps.

Correct Answer: C

Rationale: Angiotensin II receptors are in the zona glomerulosa stimulate aldosterone release (e.g., adrenal cortex). Juxtaglomerular cells produce renin not receptors. Macula densa senses lacks these. Intercalated cells manage pH not angiotensin. Adrenal location distinguishes it, key to RAAS, unlike renal or tubular sites.

Correct Answer: C

Rationale: The bicarbonate buffer system is most important rapidly neutralizes H (e.g., CO₂/HCO₃⁻ in blood). Bone buffers chronically slow. Phosphate is secondary intracellular/tubular. Proteins assist less capacity. Bicarbonate's speed distinguishes it, key to acute pH control, unlike slow or secondary systems.

Correct Answer: B

Rationale: At 5000 m, hypoxia drives hyperventilation PCOâ‚‚ falls (COâ‚‚ blown off), pH rises (respiratory alkalosis). Both lower misstates pH rises. Both higher ignores altitude false. pH fall/PCOâ‚‚ rise is hypoventilation opposite. Alkalotic shift distinguishes it, key to high-altitude response, unlike uniform or reversed changes.

Correct Answer: A

Rationale: Kidneys are retroperitoneal (behind peritoneum) not thoracic (lungs), pelvic (bladder), or pericardial (heart). This positions them anatomically, vital for surgical/radiological context, contrasting with cavity misconceptions.