Protein-mediated transport of an ion or small molecule across a membrane against a concentration gradient driven by coupling to movement of a second molecule down its concentration gradient. See also antiport and symport.

The membrane transport of a nutrient, such as glucose, in company with the movement of an ion, normally sodium; transport requires a carrier protein but does not involve direct ATP expenditure and can occur regardless of the concentration gradient for the nutrient.

Refers to transport across cell membranes where carrier is occupied by two substances simultaneously. See symport - from same side; antiport - from opposite sides.

Cotton