Sodium-Glucose Cotransport: Indirect Active Transport
Definition
The sodium-glucose cotransporter
The sodium-glucose cotransporter is a protein that moves sodium ions (Na⁺) and glucose molecules together across a plasma membrane into a cell.
- Energy Source: The movement of Na⁺ down its concentration gradient provides the energy needed to transport glucose against its gradient.
- Mechanism: Sodium ions release energy as they move down their gradient, which drives glucose into the cell without directly using ATP.
Applications of Sodium-Glucose Cotransport
- Kidney Function:
- Sodium-dependent cotransport is critical in the proximal tubules of the kidney.
- Here, cells reabsorb glucose from the filtrate to prevent it from being lost in urine.
- Maintaining Gradients:
- Glucose uptake relies on a high Na⁺ concentration outside the cell.
- This gradient is maintained by the sodium-potassium pump, which uses ATP to pump Na⁺ out of the cell while bringing K⁺ in.
