A particular epithelium has a paracellular (between the cells) pathway permeable to water and chloride. In order to enhance the net movement of NaCl and water from apical to basolateral portions of the cell, the epithelium needs: A) Basolateral Na⁺K⁺-ATPase, basolateral K⁺ channels, and apical Na⁺ channels B) Apical Na⁺K⁺-ATPase, apical K⁺ channels, and basolateral Na⁺ channels C) Basolateral Na⁺K⁺-ATPase, apical K⁺channels, and basolateral Na⁺ channels D) Apical Na⁺K⁺-ATPase, basolateral K⁺ channels, and apical Na⁺ channels E) Basolateral Na⁺K⁺-ATPase, basolateral K⁺ channels, and basolateral Na⁺ channels

Question

Quizplus · Accepted Answer

The correct choice is A because it describes the necessary components for effective NaCl and water transport across epithelial cells: a basolateral Na+/K+-ATPase to actively pump Na+ out of the cell (creating a low intracellular Na+ concentration that drives Na+ entry at the apical side), basolateral K+ channels to allow K+ to recycle back into the extracellular space (maintaining the electrochemical gradient), and apical Na+ channels to allow Na+ entry into the cell from the apical side. This setup creates a net movement of NaCl from the apical to the basolateral side, with water following osmotically through the paracellular pathway.

A Particular Epithelium Has a Paracellular (Between the Cells) Pathway