Final answer:
Absorption of sodium in intestinal epithelial cells through the sodium-potassium ATPase pump facilitates passive water absorption via an osmotic gradient. This process, known as active transport, also assists in the absorption of glucose through a Na+/glucose symporter, utilizing the sodium gradient.
Step-by-step explanation:
In intestinal epithelial cells, absorption of sodium by active transport is facilitated through the sodium-potassium ATPase pump, which drives the passive absorption of water through the osmotic gradient. Sodium ions are pumped out of the cell in exchange for potassium ions using energy derived from ATP, creating a concentration gradient.
This gradient allows for the passive reabsorption of water as well as other electrolytes like chloride, which move with the sodium ions to maintain electro-neutrality. Additionally, substances like glucose are absorbed via a Na+/glucose symporter, which uses the gradient established by the ATPase pump to facilitate glucose transport into the cell against its concentration gradient.