What provides the energy for glucose transport into intestinal mucosal cells?

• A. The active transport of sodium out of the cell by Na+/K+-ATPase
• B. Passive diffusion of glucose through GLUT transporters
• C. The ATP produced locally by glycolysis within the mucosal cell
• D. The transport of potassium into the cell via potassium channels

Answer: (A)

The energy comes from the sodium gradient across the brush-border membrane, maintained by the Na+/K+-ATPase pump. This ATP-powered pump exports Na+ and keeps intracellular Na+ low, creating a gradient that the sodium-glucose cotransporter uses to bring glucose into the cell against its own gradient. The glucose moves with Na+ into the mucosal cell via SGLT1, using the energy of the Na+ gradient rather than direct ATP use at the transport site. Once inside, glucose can exit to the blood through facilitated diffusion via GLUT transporters, which do not provide energy for uptake.