Active Transport: Energy Required
During active transport, substances move against their concentration gradient.
Active transport requires a membrane protein (carrier molecule) and energy to force the substance in a direction that it does not want to travel.
The energy for active transport is provided by ATP.
Proteins engaged in active transport are often called pumps.
Materials that are too large to move with membrane proteins and must be transported across membranes in vesicles.
The transport of macromolecules out of a cell in a vesicle is called exocytosis.
The transport of macromolecules into a cell in a vesicle is called endocytosis.