Both substances move in the same direction. For example, as sodium flows back into a cell (down its gradient), it "drags" a glucose molecule along with it (against its gradient).
Secondary active transport is arguably the "smart spender" of cellular physiology. It does not use ATP directly. Instead, it harnesses the potential energy stored in the electrochemical gradients created by primary active transport. active transport primary vs secondary
Primary active transport is the "power plant" of the cell. In this process, energy is derived directly from the hydrolysis of Adenosine Triphosphate (ATP). Both substances move in the same direction
Energy is derived from the electrochemical gradient of one solute (usually Na⁺ or H⁺) that was previously established by primary active transport. No direct ATP use. It does not use ATP directly
Because this process creates a charge or concentration gradient using direct chemical energy, primary active transport is the initiator of most cellular potential.
Calcium is a potent signaling ion. To keep cells responsive, calcium concentrations must be kept extremely low in the cytosol.