ACTIVE TRANSPORT

1. Movement of molecules or ions against the concentration gradient acroos the plasma membrane.
2. Requires both carrier proteins and the expenditure of energy to transport the molecules or ions. The energy for active transport usually comes from ATP (adenosine triphosphate)which is generated during respiration in the mitochondria.
3. The carrier protein has an active site which binds to the particular molecule or ion and another active site which binds to the ATP.
4. The carrier protein changes shape when the phosphate group from the ATP binds to it.
5. Usually, active transport results in the accumulation of or elimination of molecules or ions from the cells.
6. Carrier proteins act as pumps.





The Mechanism of Active Transport for Sodium Ions