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Encyclopedia > Vesicles

In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. Vesicles store, transport, or digest cellular products and wastes.


This biomembrane enclosing the vesicle is the same as that of the outer (cellular) membrane. They are a basic tool of the cell to organize its metabolism. Vesicles are used for digestive purposes, as transport vessels, as an enzyme storage, and as chemical reaction chambers. Many vesicles are made in the Golgi apparatus, but also in the endoplasmic reticulum, or are made from parts of the plasma membrane.


Lysosomes (membrane-bound digestive vesicles) can digest macromolecules (break them down to small compounds) that were taken in from the outside of the cell by an endocytic vesicle. This is the basic way for a cell to feed (except for photosynthesis in plants, which don't have lysosomes). The membrane of the lysosome is impermeable for lysozyme, the enzyme that does the actual digestion, to protect the cell interior from being digested by its own enzyme. Lysosomes are made in the Golgi apparatus.


Neurons store neurotransmitters in synaptic vesicles located at presynaptic terminals.

Contents

Transport vesicles

Transport vesicles can move molecules between locations inside the cell, e.g., proteins from the endoplasmic reticulum to the Golgi apparatus, and from there to the outer cell membrane, where they are secreted. They do this by budding off from one compartment and joining to another.


Anterograde transport vesicles

These are foreward moving vesicles.


Retrograde transport vesicles

These vesicles move from later to earlier cisterna.


Vesicles can be used as reaction chambers for chemical reactions that could damage the cell if they would occur in the cytosol. For example, peroxisomes are detoxifiers of hydrogen peroxide (H2O2), a toxic byproduct of cell metabolism. Large storage vesicles are known as vacuoles.


Mechanisms

Assembly of a protein coat drives vesicle formation and selection of cargo molecules.


Vesicle coat

The vesicle coat serves to sculpt the curvature of a donor membrane, and to select specific proteins as cargo. It selects cargo proteins by binding to sorting signals. In this way the vesicle coat clusters selected membrane cargo proteins into nascent vesicle buds.


See also: micelle


External links

Organelles of the cell
Chloroplast | Mitochondrion | Centriole | Endoplasmic reticulum | Golgi apparatus | Lysosome | Myofibril | Nucleus | Peroxisome | Ribosome | Vacuole | Vesicle

  Results from FactBites:
 
Biophysical Journal: Early steps of supported bilayer formation probed by single vesicle fluorescence assays (1324 words)
Therefore, bilayer formation via vesicle fusion is expected to depend on the vesicle size and is thought to occur in four steps: single vesicle adsorption, fusion of vesicles on the surface to form larger vesicles, rupture of these vesicles to form bilayer disks on the surface, and final merging of the disks.
It was our goal to directly observe vesicle fusion and rupture events at the single vesicle level to avoid ensemble averaging and to capture the multi-step processes of vesicle fusion, rupture, and extended bilayer formation with sufficient time resolution.
When the effective areal concentration of the fluorescent lipids decreases upon fusion between a labeled vesicle and an unlabeled vesicle, an increase in red TR fluorescence is observed due to the decrease in fluorescence self-quenching (dequenching); however, the green fluorescence for encapsulated CF persists.
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