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31 Cards in this Set
- Front
- Back
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What is the role of the Golgi?
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-remove and add sugars to glycoproteins with resident glycosidases and glycosyltransferases
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Why might a protein not leave the ER?
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-denatured or unfolded
-Still bound to BiP or another chaperone -If they are bad, they go out to Sec61 and get recognized by N-glycanase and taken with ubiquitin to a proteosome |
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What is the primary ER retention signal and how does it function?
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-DKEL is a short stretch
- receptors are in ER and cis-Golgi -Recycle KDEL with proteins by sending back to ER from cis (vesicles) -Needs a low pH to bind properly -its receptors have COP1 coat to take back |
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What are some chaperones in the ER and what do they do?
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-BiP (heat shock)
-calnexin, calreticulin - Prevent hydrophobic aggregates, folds proteins w/ ATP -Prevent premature exit -facilitate translocation |
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Hopw does Gycolylation occur in the ER?
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- proteins have sugar added to them after translation
- prefabricated oligosaccharide is added to the chain |
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What is the glycosylation sequence?
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-CONSENSUS
-Asn-X-Ser/Thr - attaches N-glycosidic bond to Asn sidechain via a carrier molecule. |
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How is oligosaccharide precursor made?
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-on cytosolic side, w/ 5 manose
- then flippase makes it flip to lumen side for modifications |
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What is the catalyst for glycolsylation?
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oligosaccharyl transferase
-associated with SEC61 complex. |
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Describe Glycan Trimming.
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-Originally a huigh mannose complex, 3 glucose and 1 manose are immediately removed
-more to go on in the golgi. |
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What molecules are used to remove and add sugars in the golgi, respectively?
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-Glycosidase
-glycosyltransferase |
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What is the role of the Golgi?
|
-remove and add sugars to glycoproteins with resident glycosidases and glycosyltransferases
|
|
|
Why might a protein not leave the ER?
|
-denatured or unfolded
-Still bound to BiP or another chaperone -If they are bad, they go out to Sec61 and get recognized by N-glycanase and taken with ubiquitin to a proteosome |
|
|
What is the primary ER retention signal and how does it function?
|
-DKEL is a short stretch
- receptors are in ER and cis-Golgi -Recycle KDEL with proteins by sending back to ER from cis (vesicles) -Needs a low pH to bind properly -its receptors have COP1 coat to take back |
|
|
What are some chaperones in the ER and what do they do?
|
-BiP (heat shock)
-calnexin, calreticulin - Prevent hydrophobic aggregates, folds proteins w/ ATP -Prevent premature exit -facilitate translocation |
|
|
Hopw does Gycolylation occur in the ER?
|
- proteins have sugar added to them after translation
- prefabricated oligosaccharide is added to the chain |
|
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What is the signal for glycosylation?
|
-CONSENSUS
-Asn-X-Ser/Thr - attaches N-glycosidic bond to Asn sidechain via a carrier molecule. |
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how do you make an oligosaccharide precursor?
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-on cytosolic side, w/ 5 manose
- then flippase makes it flip to lumen side for modifications |
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What enzyme catalyzes glycosylation?
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oligosaccharyl transferase
-associated with SEC61 complex. |
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How is Glycan Trimmed?
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-Originally a huigh mannose complex, 3 glucose and 1 manose are immediately removed
-more to go on in the golgi. |
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What enzymes remove and add sugars, respectively?
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-Glycosidase
-glycosyltransferase |
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What is the actual Glyco-residue that attaches to asn?
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N-acetylglucosamine (GlcNAc)
- tghen mannose then galactose |
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How do GPIs achor proteins in ER
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- They anchor to the lumen side on the C-terminal hydrophobic tail
- Used for cell coat proteins, enzymes, adhesive proteins, receptors |
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Describe both theories of Golgi structure?
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Vesicular transport- golgi is static and vesicles move cargo
Cisternal Maturation - Golgi is nynamic and a compartment rotates through. |
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What are some phagocytic cells?
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-fibroblasts - remodel connective tissue
-Macrophages and neutrophils, monocytes, granulocytes |
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Is phagocytosis a receptor mediated event? How?
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Yesm phagocyte identifies a specific or generic site and then engulf with receptor-ligands
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What role does Ca 2+ play in phagocytosis?
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-induces formation of gel-like cytoplasm during engulfment
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How does engulfment form a phagosome? Then what?
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- oxygen is metabolized to kill bacteria
-actin polymerized to extend. -acid hydriolases digest contents when a lysosome binds to the phagosome=phagolysosome |
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Why do people still get sick if phagocytosis does such a great job?
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- most pathogens are identified, but opathogen can manipulate the cell machinary
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What are ways in which a pathogen can survive phagocytosis?
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- escape from it by dissolving the membrane
-prevent fusion with lysosome- no digestion - survive in phagolysosome |
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How does a mycobacteria, TB deal with phagocytosis?
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Survives in lysosome, prevent chemotaxis
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How does Listeria work?
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-attaches to E Cadherin
-0ingested by phagocyte - secrete hemolysin, which breaks membrane - hemolysin dissolved by proteasome, but backteria free - takes over actin, and gets motility for future invasions |
