The role of carrier proteins and the transfer of energy in the transport of substances against a concentration gradient.

Intrinsic proteins in the plasma membrane act as carriers, transporting substances across the membrane.

A substance will bind to the carrier protein. The protein then hydrolyses an ATP (energy) molecule: binding to the phosphate product and using the energy from breaking the bond to change shape. This new shape is one that allows the substance to be released on the other side of the membrane.

Often, now that the carrier is open on the other side of the membrane, it will bind to molecules from there so that when it returns to its original shape, they are released over there. After the carrier protein gone back to it original shape, the phosphate ion is let go.

When the ATP is broken up ADP is produced as well as a phosphate ion. They can both be reused, and made back into ATP in respiration.

Seriously watch this, it shows the process perfectly:
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html