Na+-glucose help!

The carrier for the Na+-glucose co-transporter is located on the lumenal membrane of the intestinal mucosa and renal proximal tubule cells. Glucose is transported ‘uphill’ using the energy of the Na+ concentration gradient. The Na+/K+ ATPase maintains the inward gradient of Na+. Removing extracellular Na+ or glucose will also prevent co-transporter function. In other words, both substrates must be bound for transport to occur.

I don't think affinity for neither of these chemicals (glucose/sodium) has anything to do with how they are transported; rather, it has more to do with the gradient. Therefore, it does not necessarily have to change.

To elaborate further, the proteins affinity will change if the concentration on the inside is higher than on the outside, once again due to the gradient.

splendid. thanks! so it is definitely essential because if one is not bond then the transport will not occur. Also it doesn't have to change affinity but can.