Glucose is absorbed in the intestine along with-
Ans. is 'a' i.e., 1 Na+ * In secondary active transport, the energy is derived from the store which has been created orginally by primary active transport. Secondary active transport represents a combination of primary active transport and facilitated diffusion.* It is exemplified by glucose transport across intestinal mucosal epithelial cells, the Na+K+ pump operates at the basolateral border of the cell and maintains intracellular concentration of Na+ very low. The low intracellular Na+ concentration provides the necessory concentration gradient for Na+ to diffuse in passively at the luminal border through facilitated cotransport with glucose. Thus, the Na+K+ pump (Na+K+ ATPase) indirectly powers the movement of glucose into the cell, and glucose can move in against a concentration gradient so long as Na+ diffuses in along a concentration gradient.* It is important to know that at luminal border, Na+ is transported by facilitated diffusion (as it diffuses along a concentration gradient) while the glucose is transported actively (against a concentration gradient) and the energy is provided by Na+K+ ATPase at basolateral border - So, secondary active transport is a combination of active transport (glucose transport against concentration gradient) and facilitated diffusion (Na+ transport along concentration gradient by carrier protein).
1 Na+
2 Na+
1K+
2 K+
G.I.T.