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27 Cards in this Set
- Front
- Back
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What are the two faces of the Golgi stack? What is the difference between them?
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1. Cis golgi network- oriented towards the ER, vesicles containing newly synthesized lipids and proteins from the ER arrive at the CGN where they fuse with CGN membranes
2. Trans glogi network- proteins and lipids leave the Golgi network in transport vesicles that bud from the tip of the TGN cisternae |
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How does transport from the CGN to the TGN occur?
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1. Stationary cisterane model, shuttle vesicles carry proteins
2. Cisternal maturation model- golgi cisternae are transient compartments that graudually change from CGN to medial cisterane to TGN the two models are not mutually exclusive, both apply |
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What is anterograde transport?
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The movement of material from the ER through the Golgi toward the plasma membrane
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What is retrograde transport
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the flow of vesicles from the Golgi cisternae back toward the ER
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What is n linked glycosylation
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addition of a specific oligosaccharide to the nitrogen atom on the terminal amion group of certain asparagine residues
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What is O linked glycosylation
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addition of an oligosaccharide to the oxygen atom on the hydroxyl group of certain serine or threonine residues
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Where does glycosylation occur
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the ER and the golgi complex
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Describe core glycosylation
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All the carbodyrate chains added to proteins in the ER initaily ave a core oligosaccharide consisting of two GlcNAc. Core glycosylation begins as dolichol phosphate is inserted into the ER membrane.
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What is the significance of contranslational glycosylation
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helps to promote proper protein folding
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define calnexin
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a membrane bound Er protein that forms a protein complex with newly synthesized glycoproteins and assists in proper folding
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define calreticulin
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a soluble ER protein that forms a protein complex with a newly synthesized glycoprotein and assists in proper protein folding
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what are retention tags
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sequence on proteins that signal for retention in the ER
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what are retrevial tags
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many soluble ER proteins contian retrival tags that bind transmembrane receptors on the Golgi, when a protein containing such a tag binds to its receptor, a confirmational change occurs and the receptor ligan complex is packaged into a transport vesicle for return to the ER
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After exocytosis occurs, the ___ side of the vesicle membrane becomes the ____ side of the plasma membrane
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The inner (lumenal) side of the vesicle membrane becomes the extracellular (outer) side of the plasma membrane
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What role does calcium play in triggering exocytosis
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an elevation of intracellular calcium levels leads to the activation of protein kinases whose target proteins are components of either the vesicle membrane or the plasma membrane
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Describe receptor mediated endocytosis aka clathrin dependent endocytosis (7 steps)
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1.ligands bind to receptor
2. receptor-ligand complexes accumualte in coated pits 3. invagination is facilitated by clathrin and dynamin 4. internalized vesicle 5. loss of clathrin coat 6. becomes early endosome 7a. digestion of contents in late endosome 7b recycling receptors to plasma membrane 7c. tranport to another region of the plasma membrane and exocytosis |
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What are the two components of the clatherin lattice and what do they do?
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triskelions- structural integrity
Adaptor protein- esure that the appropriate macromolecules are concentrated into coated pits, mediate the attachment of clathrin to proteins embedded in the plasma membrane |
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What is dynamin
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a cytosolic GTPase required for coated pit construction and closing of the budding vesicle. As GTP is hydrolyzed, the dynamin rings contract and seal off the vesicle
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The specific set of proteins covering the exterior of a vescicle is an inicator of the origin and destination of the vesicle.What does clatherin do?
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selective transport of proteins from the TGN to endosomes, endocytosis of receptor ligand complexes from the plasma membrane
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The specific set of proteins covering the exterior of a vescicle is an inicator of the origin and destination of the vesicle. What does COP1 do?
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facilitates retrograde transport of proteins from the golgi back to the ER and between the cisternae of the Golgi
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The specific set of proteins covering the exterior of a vescicle is an inicator of the origin and destination of the vesicle.What does COP2 do?
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involved in transport of material from the ER to the Golgi
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What are the three things involved in vesicular trafficking according to the SNARE hypothesis
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vSNARE, tSNARE, and the coil coiled tethering protein
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What is the role of Rab GTpases in vesicular trafficking
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lock the vSNARE and tSNARE together to facilitate membrane fusion
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After the vesicle fuses to the membrane, how are the v and t SNAREs released?
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NSF and and SNAP mediate the release of the v and t SNARE
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How are tethering proteins involved in vesicular trafficking
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they act over longer distances and provide specificity by connecting vesicles to their target membranes prior to v/t SNARE interactions
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Summarize vesicular trafficking according to the SNARE hypothesis (4 steps)
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1. Vesicle is recognized and bound by tethering protein
2. Rab GTPase stimulates associate of v/t SNARE 3. v/t SNARE interact, membranes fuse 4. binding of NSF and SNAP promote disassociation of the SNARE complex |
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Describe how lysosomes develop from endosomes
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1. lysosomal enzymes are synthesize by ribosomes attached to the rough ER
2.enzymes are delivered from TGN to endosome in transport vesicles 3. early endosome matures to late endosome, drop in pH 4. activation of acid hydorlases by lowering pH |
