Biology · Homeostasis

The correct answer is B: Active secretion of hydrogen ions into the filtrate. The distal convoluted tubule (DCT) is integral to the regulation of blood pH through the active secretion of hydrogen ions into the tubular fluid, which can then be excreted in urine. This process helps to regulate the acidity of the blood, thereby maintaining homeostasis.

Option A is incorrect because glucose reabsorption occurs primarily in the proximal convoluted tubule and is not related to pH regulation. Option C is incorrect as the active secretion of sodium does not directly affect blood pH, although it is important for fluid and electrolyte balance. Option D is also incorrect because while potassium reabsorption can influence overall electrolyte balance, it does not directly contribute to the regulation of blood pH.

This option is incorrect because the distal convoluted tubule primarily functions in the regulation of electrolytes and acid-base balance, rather than glucose reabsorption, which mainly occurs in the proximal convoluted tubule.

This is the correct option, as the distal convoluted tubule plays a crucial role in maintaining acid-base balance by actively secreting hydrogen ions into the filtrate, which helps to lower blood acidity.

This option is incorrect because while sodium reabsorption does occur in the distal convoluted tubule, it is not primarily responsible for the regulation of blood pH.

This option is also incorrect because the reabsorption of potassium ions is not a direct mechanism for regulating blood pH, even though potassium balance is important for overall homeostasis.