2. electrochemical potential gradient Requires __ down an no input of metabolic energy . Uses a membrane carrier and exhibits all the characteristics of carrier-mediated transport. A) Primary active transport B) S econdary active trans port Na+/K+ATPase ) Facilitated diffusing None of the above

The correct answer is B) Secondary active transport.<br /><br />Secondary active transport, also known as cotransport, uses the energy from the movement of one molecule down its electrochemical gradient to drive the transport of another molecule against its gradient. This process does not require direct ATP hydrolysis but still uses the energy stored in the electrochemical gradient. It typically involves a membrane carrier protein that facilitates the transport of both molecules.