Vesicular Transport Flashcards
The release of soluble proteins
secretion
adding materials to the cell surface and extracellular space
exocytosis
subtracted materials to the cell surface and extracellular space
endocytosis
Explain Cargo selection
coat proteins (COPI, COPII) bind to the signal sequences on the tails of cystolic proteins and they group into donor compartments
Explain budding
Adaptor proteins make a mesh-like lining around the group, the bundled proteins change shape and bulge in
Explain scission and uncoating
Scission proteins tighten the neck until the vesicle buds off. Uncoating unbundles the donor compartment.
Explain Transport and Tethering
Vesicles are transported via microtubule or actin filaments. Then Rab proteins on the vesicles bind to tether proteins on the acceptor membrane and “search” for the correct acceptor compartment.
Explain Docking, Fusion, and Disassembly
v-SNAREs bind to t-SNARES, fusion to the acceptor compartment occurs. NSF and SNAP disassemble the SNARES
Traffic cop for the Cell
Golgi
cis/trans face
cis faces nucleus/trans away from
CGN
cis-Golgi network, the largest cisternae
Explain bulk transport
Carrying non specific cargo, happens frequently in ER to Golgi transport
ER retention signal
marker for ER proteins that need to be returned from the golgi
Golgis coat proteins?
COPII from ER, COPI within the Golgi
Explain the bilayer thickness model
proteins with short transmembrane domains go to the Cis, medium length domains to middle cisternae, and longer domains to the trans-cisternae
How does the Golgi select cargo? (4 ways)
post-translational modifications, protein kin recognition, signal-receptor method, lipid raft
How does the Golgi bud? (3 ways)
binding of phospholipids makes a curve, modification of the phospholipids, phospholipid asymmetry
Dynamin
forms a loop and cinches off vesicles in golgi
What is constitutive secretion?
the (uncontrolled) foundation for all secretion
What are zymogen granules?
where concentrated forms of secreted materials are stored.
What is clathrins role?
Condenses around cargo receptors, makes a coated pit, makes a vesicle that is released by hsp70 after meeting auxillin.
What do endosomes do?
They are a collection of sorting compartments that separate receptors from cargo and send the receptors back out
vesicle specificity in early endosome?
EEA-1, t-SNARE, Rab5, PIP3 complex
What happens after the vesicle fuses with the endosome?
lower pH dissolves it and unbinds molecules
Describe a late endosome
pH below 6.0, eventually becomes a lysosome
A pathway that can be utilized for either endocytosis or exocytosis
ER-CGN-GOLGI-TGN
What sorting signal does the TGN use?
M6P
Why is N-glycosilation necessary?
Without N-glycosilation in the ER, the Golgi can’t create MP6, and there would be no cellular contribution to the endosomes and lysosomes.
At what pH does an endosome become a lysosome?
5.0
glycosidases nucleases phosphatases, phospholipases?
digestion of complex oligosaccharides on glycoprotiens ; nuclease-DNAse II digest nucleic acids
phosphatases- digest phosphates from nucleic acids
Phospholipases- digest membranes
Why don’t phospholipases digest the membranes of lysosomes?
lysosomal integral membrane proteins (LIMPs) and
lysosomal associated membrane proteins (LAMPs) are Heavily glycosilated by a sugar coat called a glycocalyx
MVB
A vesicle inside a vesicle, ubiquitination has occurred, going to be digested.
What organelle is at the heart of the EM system?
Golgi
What is RAB?
GTPase
How are proteins retained in the Golgi?
kin groups aggregate, bilayer thickness
How can the bilayer be at different thicknesses?
variations in cholesterol
