Which part of the Na /Glucose symporter in the apical surface of an epithelial cell would you mutate so that it can transport fructose instead of glucose into the cell

The binding site for glucose

Explanation:

Symporters are integral membrane proteins that control the entry and exit of a specific type of molecule across the cell membrane in a mode that is dependent on the transport of a second specific type of molecule in the same direction. Symporters are membrane cotransporter proteins involved in active transport, i.e.., they require energy (usually in the form of ATP) to transport substances in the same direction. The Sodium (Na+)-Dependent Glucose Transporter 1 (SGLT1) is a cotransporter involved in the transport of glucose across cell membranes of enterocyte intestinal absorptive cells. For such purpose, SGLT1 contains two Na+-binding site sites, one of them overlapping the glucose-binding site. It has been shown that mutations at the glucose-binding site may alter the ability of SGLT1 to transport glucose.

the answers are a and c