Answer:
Secondary active transport protein
Secondary active transport proteins, like the sodium-glucose pump, are responsible for moving molecules across the cell membrane using the energy obtained from an electrochemical gradient. In the case of the sodium-glucose pump, it transports glucose into the cell against its concentration gradient by using the energy released when sodium ions move down their concentration gradient.
This process occurs in the epithelial cells of the intestines, allowing for efficient absorption of glucose from the intestinal lumen. The pump helps maximize glucose absorption by using the energy of sodium ions to transport glucose into the cell, even when the concentration of glucose inside the cell is higher than outside.
So, the sodium-glucose pump is an example of a secondary active transport protein because it couples the movement of glucose with the movement of sodium ions, utilizing the existing concentration gradient of sodium ions as a source of energy.