Absorption by which of the following is linked to active sodium absorption at the basolateral border of epithelial cell?
The correct answer and explanation is:
The correct answer is glucose absorption.
Explanation:
In epithelial cells of the intestinal lining and kidney tubules, absorption of various substances is often coupled with the active transport of sodium ions (Na⁺). This mechanism is crucial for maintaining the balance of electrolytes and nutrients within the body. Active sodium absorption occurs at the basolateral membrane of these cells, meaning the side of the cell that faces the bloodstream rather than the lumen (inside) of the organ.
The coupling of sodium absorption with glucose absorption is a common example of co-transport, also known as symport. In this process, sodium ions are actively pumped out of the epithelial cell by the sodium-potassium pump (Na⁺/K⁺ ATPase) on the basolateral membrane, creating a sodium gradient. This gradient is essential for secondary active transport. On the apical (lumen-facing) side of the cell, sodium ions are brought back into the cell along with glucose molecules through a sodium-glucose co-transporter (SGLT1 or SGLT2, depending on the organ). The energy from the sodium gradient drives the uptake of glucose against its concentration gradient.
This mechanism is highly efficient and essential for nutrient absorption in the small intestine. In the kidney, it plays a critical role in reabsorbing glucose from the filtrate in the proximal convoluted tubule, helping to prevent glucose loss in urine.
The active transport of sodium thus provides the necessary energy for glucose to be absorbed effectively, and this process exemplifies the interdependence of ion gradients and nutrient uptake within epithelial cells.