Biology - Excretory Products and their Elimination Question with Solution | TestHub

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.