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18 Cards in this Set
- Front
- Back
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What is protein targeting? |
Direct proteins to the right destinations Either during or after synthesis |
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Whati s protein sorting? |
Directing proteins to the secretory pathways ER, GOLGI LYSOSOMES. |
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You always start where with protein making |
cytosol because thats where RNA ribosomes are |
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If you dont say in the cytosol you go to? |
ER, mito, then sorting again for GOLGI, lysosomes |
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Nonsecretory = Secretory = |
lyososmes endosomes outside of the cell (plasma membrane) |
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Secretory pathway means you must travel across? And Non secret? |
ER lumen You stay in the cytosol |
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How can you tell the difference between cytosol and lumen? |
cytosol have ribosomes in it. Thus black circles while lumen is nice and flat. |
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Tubulesare sometimes called |
cisterna (folds) |
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What are microsomes? |
Basically functional bits of the ER |
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Are proteins undergoing co-translational transport |
Yes (explain the diagram) |
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How does co-translational transport work? |
mRNA binds to a ribosome in the cytosol. N-terminus binds to SRP. (signal recognition particle). This then brings it to the ER membrane (due to SRP receptor alpha and beta). Using hydrolysis of GTP, it opens up the translocon and causes the SRP and SRP receptor to disassociate so the ribosome can go closer to the translocon. Peptide is then translated inside the ER lumen. Signal peptidase come and cleave the isgnal off. |
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How to motify your protein in the ER? (4) |
Proteolytic cleavage : Cleaving the signal Gylcosylation(adding sugars) - important for proteins outside of the cell to allow them to stick together. Adding disulfide bonds Folding with chaperone proteins. |
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What are the 3 sugars added in the ER. |
Glucose mannose, acetyl-glucasomine. |
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Process of gylcosylation? |
olgiosaccharyl transferase will transfer it from the colichol carrier to the protein/ ALmost always on the asparagine residue on the protein. # of glucose/manose is specific to each protein. Glycosidase will remove sugar to match it. |
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Benefits of gylcosylation? |
Protein folding stability adhesion |
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How does Formation of disulfide bonds work in the ER |
Usually on cyestine a protein called PDI (protein disulfide isomerase) directs what sulfide bonds to what sulfide and reduces the protein. Protein is reduced in the beginning, PDI is oxidized. PDI oxidizes the protein (final) and PDI becomes reduced. To oxidize the PDI to get it reduced, Ero1 is used. Ero1 uses oxygen to reconvert itself. |
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Explain protein folding |
Lumen is hydrophillic. Protein has hydrophobic regions. BiP will bind onto hydrophobic regions protecting it(chaperone protein BiP) Lectins(calnexins and calreticulin) bind to the sugars. Sugars are charged and could interact with things you dont want. PDI is again working on the sulfides. |
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TOM and TIM? |
Target outer membrane Inner target membrane |
