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Active transport
Vesicular transport. Vesicular transport is the active movement of
substances
across the cell membrane via a vesicle. In exocytosis,
materials in the intracellular fluid are engulfed by a vesicle
which then secretes or empties the contents of the vesicle
into the extracellular fluid. In endocytosis,
materials from the extracellular fluid are engulfed by a vesicle
which then empties its contents in the intracellular fluid.
In exocytosis materials in the intracellular fluid
are engulfed by a vesicle which then secretes or empties
the contents of the vesicle into the extracellular fluid.
First
a vesicle containing materials to be transported approaches the plasma
membrane
guided by the cytoskeleton. The vesicle then fuses with the plasma membrane
and empties its contents into the extracellular space.
In endocytosis, materials in the extracellular fluid
are engulfed by a vertical which then empties its contents into the
intracellular fluid.
First, molecules approach the plasma membrane from the extracellular side.
Plasma membrane invaginates to take in the molecules
forming a vesicle in the intercellar space.
Phagocytosis is a special type of endocytosis in which larger particles are engulfed by
the cell.
For example, bacteria are consumed by white blood cells in this way
First, the plasma membrane invaginates
to take in the particles forming a vesicle in the intracellular space. Soon
after formation
of the vesicle, a lysosome joins the vesicle, emptying
digestive enzymes into the vesicle to break down the particle.
Pinocytosis is a special type of endocytosis in which the cell takes in
extracellular fluid. Typically the fluid taken in by pinocytosis
is rich in nutrients. The plasma
membrane invaginates to take in the fluid forming a vesicle in the intercellular
space.
In receptor-mediated endocytosis molecules first approach a specialized
area of the plasma membrane equipped with cell surface receptor proteins.
Only molecules matching the shape of the receptors will bind to the receptors.
First, the area
the plasma membrane where molecules are bound to receptors invaginates
creating a vesicle inside the cell.
Then,
new cell surface receptor proteins are manufactured by the cell to
replace those used up in vesicle formation.