Cell Biology- Protein Traficking

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  • Created by: KayshaN
  • Created on: 22-10-19 10:39
What are the three main mechanisms of membrane bound organsims import proteins?
1) move between nucleus + cytosol through nuclear pores 2) Transmembrane protiens translocators 3)Vesicular Transport
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What helps direct a protein to the ER?
ER Signal Sequences, comprised of 16-30AA, one+ positve charged plus 6-12 hydrophobic
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Which end of the Polypeptide is the signal sequnece bound to?
N-Terminus
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What is the signal sequence bound to and what does this do?
Signal Recognistion Particle (SNP), wraps around ribosome and stops protein synthesis, gives enough time for it to be recognised by ERmebrane and bind to SRP receptor
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After the protein associates with the translocon, what happens to SRP?
Dissociates and protein synthesis can begin again
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Why is is important for the SRP to stop protein synthesis? (2)
1)stop lysosomal enzymes from being in the cytopaslm 2)avoids large sturtures portiens forming before associate with translocon
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What properties of the signal sequence anchor it to the translocon?
hydrophobic nature
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What happens after the signal sequence is anchored to the translocon?
more amino acids are added, pushed through into lumen of ER
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How does the protein become free in the lumen of the ER?
ER Resident Enzymes cleaves off where signal sequence meets polypeptide.
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What is the name of the specific translocon nvolved in this?
Translocator= Sec61
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How does the process differ for Integral Proteins?
There are a run of hydrophobic amino acids that form a alpha helices acts as a stop sequence.(cleaves)
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How does N-Linked Glycosylation Occur in the ER?
ER resident enzymes add a carbohydrate chain from glycolipid (cleave) to AA Asparagine in a protien that is pushed through.
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What is Cathrin?
Vesicle coat, 3 come together to form triskeleton strutre and interlock.
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Describe how Catherin drives vescile formation.
Catherin adaptor proteins associate with peripheral proteins (that are associated with cargo). Creates a catherin, peripheral, integral and cargo complex. Induces curvature and bending. Vescile is almost formed, deatches from donor and detaches clath
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How do vesicles deatch from the donor?
Dynamins, warap around neck of forming vesicle, fuse.
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Outline the Role of Two Types of Molecules in Vesicle Fusion.
Integral v-SNARE protein and Rab-GTR (peripheal lipid anchor) associated with vesicle. On target there are t-SNAREs and Rab Effector. Rab GTR associates to Rab Effector, t-SNARE recognises v-SNARE and interwind, conformation, vesciles closer fusion.
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Two states of RAB?
1) Bound to GTP-on state 2)Bound to GDP- off state
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How do soluble ER-Resident Protiens get reatined in the ER?
KDEL Sequences
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What is a KDEL Sequence?
AA Sequence Lys-Asp-Glu-Leu on C-terminus
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How does the KDEL sequence complete its function?
KDEL receptor proteins on ER, trafficing process means ER resdient proetins may be moved to golgi in vesicles coated COP2, trafficed back from golgi, because KDEL receptors also trafficed- retrival mechanism
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What is exocytosis?
secretion, vescile with cargo, docking, fusion, out e.g. histamine released by mast cells fuse when stimulated e.g. pollen
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How are substances trafficed to Lysosomes?
Mannose-6-Phosphate Pathway (M6P)
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Outline Steps of M6P Pathway
1) ER and Golgi lysosomal enzymes undergo N-glycolysation 2)Mannose residues on carb side chain added in golgi 3)golgi network contain M6PRs bind to enzymes containing M6P 4) Enzymes bound to M6PR are packaged transported to late endosome, enzyme dis
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What is endocytosis?
Engluf part external environment
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Outline Recepetor Mediated Endocytosis
receptors on surface recognise molecules outside, interaction cluster together, formation of clatherin, formation vesicle, dynamin pinch off, vesicles trafficed (Rab, Snares), different things happen
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What is Transcytosis?
take up one side of the cell and released other side e.g. antibodies across placental cells, vesicles called caveolae
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Example fo Receptor Mediated Endocytosis...
Cholestrol: Conditon Familial hypercholestrolemia, high levels in blood, inherited gene- high levels of low density lipoprotien complex (LDL), cholestrol packages , adaptin binds LDL tail receptors, clath, invaginates, uncoats, lysosome mutant-no ada
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Other cards in this set

Card 2

Front

What helps direct a protein to the ER?

Back

ER Signal Sequences, comprised of 16-30AA, one+ positve charged plus 6-12 hydrophobic

Card 3

Front

Which end of the Polypeptide is the signal sequnece bound to?

Back

Preview of the front of card 3

Card 4

Front

What is the signal sequence bound to and what does this do?

Back

Preview of the front of card 4

Card 5

Front

After the protein associates with the translocon, what happens to SRP?

Back

Preview of the front of card 5
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