vesikel trafik - kbk rahman

8/11/2019 Vesikel Trafik - Kbk Rahman

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By

Dr.H.Abd Rachman Tanjung AIFM

BAGIAN FISIOLOGI

FAKULTAS KEDOKTERAN UISU


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Vesikel transport

transport vesikel dari satu kompartemen dan menyatudengan kompartemen lainnya

Membawa material dari lumen dan membrane donor kelumen dan membrane target kompartemen yang lain


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The Molecular Mechanisms of Membrane Transportand the Maintenance of Compartmental Diversity

Transport processes mediate a continual exchangeof components between the ten or more chemically distinct,membraneenclosed compartments that collectively comprisethe biosyntheticsecretory and endocytic pathways.

The enclosing membrane: molecular markers displayed on thecytosolic surface of this membrane serve as guidance cuesfor incoming traffic and ensure that transport vesicles fuseonly with the correct compartment, thereby dictating thepattern of traffic between one compartment and another.


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Types of Coated Vesicles

There are three wellcharacterized types of coatedvesicles, which differ in their coat proteins:1. clathrincoated: mediate transport from the Golgi

apparatus and from the plasma membrane2. COPI

coated: mediate transport from the ER andthe Golgi cisternae

3. COPIIcoated vesicles ---- > from rough ER to golgi


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Utilization of different coats in vesicular traffic

Different coat proteins

- select different cargo and- shape the transport vesicles

that mediate the various steps in thebiosyntheticsecretory andendocytic pathways.


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The assembly and disassembly of a clathrin coat


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LysosomesAre the Principal Sites of Intracellular Digestion

Lysosomes are membraneenclosed compartments filled withhydrolytic enzymes that are used for the controlled intracellulardigestion of macromolecules.

They contain about 40 types of hydrolytic enzymes,includingproteases, nucleases, glycosidases, lipases, phospholipases,

phosphatases, and sulfatases. All are acid hydrolases.

For optimal activity they require an acid environment, and thelysosome provides this by maintaining a pH of about 5.0 in itsinterior. In this way, the contents of the cytosol are doubly

protected against attack by the cell's own digestive system.The membrane of the lysosome normally keeps the digestiveenzymes out of the cytosol, but even if they should leak out, theycan do little damage at the cytosolic pH of about 7.2.


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The sequestration of endocytosed proteins into internalmembranes of multivesicular bodies.

Eventually, all of the internalmembranes produced by theinvaginations shown are digested by proteases and lipases inlysosomes.

The invagination is essential toachieve complete digestionof endocytosed membrane proteins.

Because the outer membrane of themultivesicular body becomescontinuous with the lysosomal membrane, lysosomal hydrolasescould not digest the cytosolic domains of transmembrane proteinssuch as the EGF receptor shown here, if it were not for the

invagination.


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THE FORMATION OF SYNAPTIC VESICLES.

These tiny uniform vesicles are found only in nerve cells and insome endocrine cells, where they store and secrete small moleculeneurotransmitters.

The import of neurotransmitter directly into the small endocyticvesicles that form from the plasma membrane is mediated bymembrane carrier proteins that function as antiports, being drivenby a H+ gradient maintained by proton pumps in the vesiclemembrane


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DAAAAAA ......................

vesikel trafik - kbk rahman

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