Active and Passive Transport

Passive Transport Versus Active Transport

Passive transport involves carriers, channels, or direct diffusion through a membrane.
This type of transport always operates from regions of greater concentration to regions of lesser concentration.
No external source of energy is required.

Examples of passive transport include
·Simple diffusion
·Channel diffusion
·Facilitated diffusion


In active transport it is possible to go against the concentration gradient.
In active transport, a source of energy is required to move the carrier and its materials.










Endocytosis is a general term for a group of processes that bring macromolecules, large particles, small molecules, and even small cells into the eukaryotic cell. There are three types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis. In all three, the plasma membrane invaginates (folds inward) around materials from the environment, forming a small pocket. The pocket deepens, forming a vesicle. This vesicle separates from the plasma membrane and migrates with its contents to the cell’s interior.


Exocytosis is the process by which materials packaged in vesicles are secreted from a cell when the vesicle membrane fuses with the plasma membrane. The initial event in this process is the binding of a membrane protein protruding from the cytoplasmic side of the vesicle with a membrane protein on the cytoplasmic side of the target site on the plasma membrane. The phospholipid regions of the two membranes merge, and an opening to the outside of the cell develops. The contents of the vesicle are released to the environment, and the vesicle membrane is smoothly incorporated into the plasma membrane.