Final answer:
Option (a), The statement about the glucose-Na⁺ symporter using the Na⁺ gradient for active glucose transport into the cell and opening towards the cytosol to release both Na⁺ and glucose is true, exemplifying secondary active transport.
Step-by-step explanation:
The statement about the glucose-Na⁺ symport protein using the electrochemical Na⁺ gradient to drive the active transport of glucose into the cell is TRUE. Once the transporter has bound both Na⁺ and glucose, it does indeed preferentially open toward the cytosol, allowing it to release both solutes within the cellular environment.
This process is known as secondary active transport, where a sodium-potassium pump maintains the sodium ion gradient that is necessary for the function of the symporter. The energy derived from the movement of Na⁺ down its electrochemical gradient is utilized to transport glucose into the cell against its own concentration gradient.