Biology – 3.3 Active transport | e-Consult

Statement: Protein carriers facilitate the movement of specific molecules or ions across a cell membrane during active transport.

Energy Requirement: Active transport requires energy because the movement of molecules against their concentration gradient necessitates overcoming the natural tendency for molecules to diffuse down their concentration gradient. This energy is typically supplied in the form of ATP (adenosine triphosphate). ATP hydrolysis provides the energy needed to change the conformation of the protein carrier.

Role of the Protein Carrier: The protein carrier forms a specific complex with the molecule or ion being transported. This binding causes the carrier protein to undergo a conformational change, which physically moves the molecule/ion across the membrane. The conformational change is driven by the hydrolysis of ATP. The carrier then releases the molecule/ion on the other side of the membrane, returning to its original conformation, ready to bind another molecule/ion. The specificity of the carrier ensures that only the intended molecule/ion is transported.