Final answer:
Secondary active transport occurs by two mechanisms: symport and antiport. It uses the electrochemical gradient established by primary active transport to move other substances in or out of the cell.
Step-by-step explanation:
Secondary active transport occurs by two mechanisms: symport and antiport.
Symport mechanisms move two or more substances in the same direction at the same time, while antiport mechanisms move two or more substances in opposite directions across the cell membrane.
Secondary active transport uses the energy of the electrochemical gradient established by primary active transport to transport other substances into or out of the cell.