Sodium-glucose cotransporters use sodium gradients to move glucose into epithelial cells by indirect active transport; This mechanism explains glucose recovery in kidney tubules and intestinal absorption.
Coverage 2014–2014 · Updated 15 Jul 2026
A sodium-dependent glucose cotransporter uses downhill sodium entry to move glucose into an epithelial cell against the glucose gradient—indirect or secondary active transport.
The cotransporter binds both solutes and changes conformation. A basolateral sodium-potassium pump uses ATP to keep intracellular sodium low, storing the energy that sodium later releases as it enters through the cotransporter.
| Site | Function |
|---|---|
| Small-intestine epithelium | Absorbs glucose from the gut lumen into epithelial cells |
| Nephron epithelium | Reabsorbs filtered glucose so it can return to the blood |
Glucose can enter an intestinal epithelial cell even when its concentration is already higher inside, provided sodium moves inward down the gradient maintained by the sodium-potassium pump.
The cotransporter does not hydrolyze ATP directly, but transport still depends on ATP indirectly through maintenance of the sodium gradient.
This objective is assessed through multiple choice, commonly using Identify.
Identify
Teaching content should connect that answer to the mechanism: sodium moves down its gradient, glucose is carried with it, and the cell later moves glucose onward.
Representative question
What transport method is used in the reabsorption of glucose in the proximal convoluted tubule of the kidney?
Diffusion
Osmosis
Endocytosis
Active transport
The HL extension asks how membrane structure becomes dynamic cell behaviour. Fatty acid saturation and cholesterol tune fluidity. Fluid membranes form and fuse vesicles. Gated ion channels and sodium-potassium pumps create nerve-cell gradients and electrical responses. Sodium-dependent glucose cotransport uses a sodium gradient to move glucose indirectly against its gradient. Adhesion molecules organize tissues.
