Dear Syed,

Cotransport is usually considered as secondary active transport. One molecule is moving down its concentration gradient (in a passive manner) for carrying a second molecule with it against the second molecule's concentration gradient. Moving the second molecule against its concentration gradient requires energy, which is supplied by the concentration gradient of the first molecule. Often this gradient is supplied by actively transporting the first molecule across the membrane in a separate active transport process - thus cotransport is called ta secondary active transport (as in, dependent upon this primary active transport process).

Hoping this will be helpful,

Rafik

Dear Raju,

Cotransporters are protein pumps used to export or import small molecules. Cotransport is also called as secondary active transport, which means that electrochemical gradient is used as a means of energy instead the involvement of any ATP. It works by binding to two molecules or ions at a time and using the gradient of one solute's concentration to force the other molecule or ion against its gradient.  In some cases the electrochemical gradient for cotransport is due to the movement of Na + and H+ ions. This powers the movement of another substance that is pumped either in or out, against the concentration gradient. An example is the movement of glucose. In order for the transportation of glucose to be in the opposite direction of the concentration gradient, sodium ions are needed. 

On the other hand, the primary active transport uses chemical energy like ATP.

So, as ATP is not directly involved in the functioning of a cotrnsporter then cotransport cannot be considered as an active transport.

Sayeed