Secondary active transport is a crucial mechanism for many cells, and there are several examples of its importance:
Outside (High Na⁺) → [Na⁺ + Glucose] → Inside (Low Na⁺) secondary active transport
| Approach | What it tests | | :--- | :--- | | | Remove external Na⁺ → transport stops (proves Na⁺ dependence) | | Oubain (Na⁺/K⁺ pump inhibitor) | Transport gradually stops as Na⁺ gradient collapses (indirect proof) | | Valinomycin (K⁺ ionophore) | Changes membrane potential; affects electrogenic transport | | Vesicle assays | Load vesicles with high Na⁺ inside, then add external substrate – uptake occurs without ATP | Secondary active transport is a crucial mechanism for