Specific proteins responsible for the flow of materials and...

Active transport is the uphill movement of materials across the membrane where the solute particles move against their concentration gradient or electro-chemical gradient. It takes place through the agency of special organic molecules called carrier molecules, carrier particles or carrier proteins. There is a special carrier molecule for each solute particle (ion or molecule). The carrier has its binding site on two surfaces of the membrane. The solute particle (or substrate) combines with the carrier to form carrier solute complex. In the bound state the carrier undergoes a conformational change which transports the solute to the other side of the membrane. Here the solute is released. Energy is used in bringing about the conformational change in the carrier. It is provided by ATP.