Final answer:
To complete the epithelial transport system for sodium and glucose, both a sodium channel and a potassium channel on the basolateral membrane domain are necessary, making option .
Step-by-step explanation:
The complete epithelial transport system for sodium and glucose requires additional components beyond just sodium and glucose transporters. Based on the functions and requirements of the epithelial cells in the PCT (proximal convoluted tubule), the full system necessitates both a sodium channel on the basolateral membrane domain for sodium exit and a potassium channel on the same domain to maintain ionic balance and resting membrane potential. Thus, the correct answer is option D, both A and B.
These channels serve several roles: sodium channels allow sodium, actively pumped into the interstitial fluid by the Na+/K+ ATPase, to leave the cell and maintain a low intracellular sodium concentration. This gradient drives the uptake of sodium and glucose from the apical side. The potassium channels allow potassium to return to the interstitium after being pumped into the cell by the Na+/K+ ATPase, thereby maintaining the cell's electrical neutrality and preventing excessive buildup of potassium.
Although a leak pathway for chloride ions through the tight junctions (option C) is significant in certain nephron segments, it is not a component that completes the epithelial transport model of sodium and glucose as described.