Question

active transport processes require energy, either directly or indirectly. a primary active transporter, or atpase, directly hydrolyzes adenosine triphosphate (atp) and uses this energy to move ions against their electrochemical gradients. the sodium - potassium pump, or na⁺/k⁺ atpase, is a very important primary active transporter within the plasma membranes of every cell in the body. this antiporter sequentially moves three sodium ions out of the cell and two potassium ions into the cell. secondary active transport couples the movement of an ion down its electrochemical gradient with the movement of another ion or molecule against its concentration gradient. this paired movement occurs once both molecules bind to the transporter. sodium is often the ion powering this movement because of its steep concentration gradient maintained by the na⁺/k⁺ atpase. the directional movement of the actively transported solute is always against its concentration gradient. movement of this solute may occur either in the same direction as the ion moving down its concentration gradient (called symport or cotransport) or in the opposite direction (called antiport, exchange, or countertransport).

1. primary and secondary active transport proteins differ in that primary active transport proteins ___.

• move both molecules down their gradients, while secondary active transport proteins move both molecules against their gradients
• move both molecules against their gradients, while secondary active transport proteins couple the movement of an ion down its gradient with the movement of another molecule against its gradient
• move both molecules against their gradients, while secondary active transport proteins move both molecules down their gradients
• move both molecules down their gradients, while secondary active transport proteins couple the movement of an ion down its gradient with the movement of another molecule against its gradient

1. the na⁺/k⁺ atpase moves sodium in the ___ direction compared with the direction it travels through sodium leakage channels.

• opposite
• same

Explanation:

1. The text states that primary active transporters directly use ATP to move ions against their electrochemical gradients, while secondary active transport couples the movement of an ion down its electrochemical gradient with the movement of another ion or molecule against its concentration gradient.
2. Sodium - potassium pump ($Na^+/K^+$ ATPase) moves sodium out of the cell against its concentration gradient, while sodium leakage channels allow sodium to move into the cell down its concentration gradient.

Answer:

1. B. move both molecules against their gradients, while secondary active transport proteins couple the movement of an ion down its gradient with the movement of another molecule against its gradient
2. A. opposite