Q57 / 200 · MHT CET - Medical 2026 (21 April Shift 1) · Biology

Select the INCORRECT statement related to tubular secretion.

  • A
    Tubular secretion is the only mode of excretion in marine bony fishes and desert amphibians.
  • Correct answer
    B
    Tubular secretion helps in changing the pH of urine from acidic to alkaline.
  • C
    During tubular secretion, cells of distal convoluted tubule actively absorb creatinine, $\text{K}^+$, $\text{H}^+$, etc. from peritubular capillaries.
  • D
    During tubular secretion, cells of distal convoluted tubule secrete creatinine, $\text{K}^+$, $\text{H}^+$ etc. from peritubular capillaries into lumen of DCT and CT.

Solution

Tubular secretion involves the active transport of substances like $\text{H}^+$, $\text{K}^+$, ammonia, and creatinine from the peritubular capillaries into the lumen of the renal tubule.

The secretion of $\text{H}^+$ ions into the filtrate helps in maintaining the acid-base balance of the body fluids and makes the urine acidic (pH around 6.0). Therefore, tubular secretion changes the pH of the filtrate from slightly alkaline (blood pH 7.4) to acidic, not from acidic to alkaline.

Marine bony fishes and desert amphibians often have aglomerular kidneys to conserve water, making tubular secretion their primary or only mode of excretion.

Thus, the statement claiming tubular secretion changes the pH of urine from acidic to alkaline is incorrect.

Answer: Tubular secretion helps in changing the pH of urine from acidic to alkaline.

Hence, the correct answer is option: 'B'.

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