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During the absorption of glucose in the small intestine, glucose enters the epithelium by Na+/glucose co-transporter by the concentration gradient of Na+. The gradient is generated by pumping 3Na+ out each time and the entrance of 2K+ by Na+/K+ pump. The K+ is then removed by the concentration gradient via the potassium channel protein.

My question is is it more favorable to use a Na+ channel protein to pump Na+ out of the cell to generate the concentration gradient? Or there are some biological significance for K+ to enter the cell and leave again repeatedly (e.g. maintain stable charge distribution in and out of the cells? Thank you.

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Na+ channel proteins would not be able to generate a concentration gradient, as they are passive transporters, not pumps. They essentially can only facilitate diffusion of Na+ down a gradient. The Na+/K+ pump is ATP-driven, providing active transport needed to establish or maintain a concentration gradient.

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