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For this reason, vesicles are a basic tool used by the cell for organizing cellular substances. Vesicles are involved in metabolism, transport, buoyancy control, [2] and temporary storage of food and enzymes. They can also act as chemical reaction chambers. Sarfus image of lipid vesicles
[1] [2] They are spherical vesicles that contain hydrolytic enzymes that digest many kinds of biomolecules. A lysosome has a specific composition, of both its membrane proteins and its lumenal proteins. The lumen's pH (~4.5–5.0) [3] is optimal for the enzymes involved in hydrolysis, analogous to the activity of the stomach.
The Golgi apparatus (/ ˈ ɡ ɒ l dʒ i /), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. [1] Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination.
Vesicles also transport molecules directly back to the plasma membrane, but many molecules are transported in vesicles that first fuse with recycling endosomes. [19] Molecules following this recycling pathway are concentrated in the tubules of early endosomes.
COPI vesicles also play a key role in the movement of Golgi-resident enzymes between different Golgi compartments, ensuring that each compartment maintains the necessary enzymes for proper modification of cargo proteins. [7] Once vesicles reach the Golgi, they undergo further modifications, including glycosylation and proteolytic processing. [7]
In cell biology, microsomes are heterogeneous vesicle-like artifacts (~20-200 nm diameter) re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.
Vesicles sent off by the ER containing proteins are further altered at the Golgi apparatus and then prepared for secretion from the cell or transport to other parts of the cell. Various things can happen to the proteins on their journey through the enzyme covered space of the Golgi apparatus.
Microbody structure - a peroxisome. Microbodies are different type of bodies present in the cytosol, also known as cytosomes. A microbody is usually a vesicle with a spherical shape, ranging from 0.2-1.5 micrometers in diameter. [1]