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33 Cards in this Set
- Front
- Back
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What are 3 nutrients taken up by vesicular endocytosis?
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LDL, HDL (lipoproteins) and Fe
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What types of molecules are taken up by vesicular endocytosis?
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Nutrients, hormones, pathogens
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By how much does cell surface receptors increase the efficiency of endocytosis uptake?
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1000 percent
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What specialized endocytic structures collect endocytic receptors, but not other membrane proteins?
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Clathrin coated pits
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What happens when Clathrin Coated pits don't work?
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Reduced binding to cargo (LDL)
Defective cytoplasmic tails |
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What do Clathrin adaptor complexes do?
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Mediate interaction between receptors and clathrin
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Describe the structure of Clathrin.
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Heavy chains with hinged rods
Light chains are accessory proteins Heterohexamer unit |
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What to Clathrin light chains do?
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They regulate triskelia polymer formation which forms a big network of hexagons and pentagons.
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Where is the AP-2 clathrin adaptor?
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The cell surface on the plasma membrane.
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Where is the AP- 1 Clathrin adaptor?
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The trans-golgi network.
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Describe the structure of Clathrin adaptors.
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heterotetramers
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What is adaptin?
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a clathrin adaptor
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Describe a Clathrin-coated pit signal.
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-Receptors have a 4 amino acid motif that attracts the coated pit proteins
- protruding loop -Tyr or other aromatic amino acid. |
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Name the steps of the Clathrin cycle.
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1. Adaptor protein recruited to cytoplasmic plasma membrane
2. Triskelia bind to adaptor 3. Triskelia mediates membrane budding, invagination occurs with GTPase 4. Heat shock protein ATPase mediates uncoating of triskelia 5. triskelia goes back to PM or golgi |
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What is the GTPase and the ATPase required for the clathrin cycle?
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GTPase- dynamin for fission step
ATPase- hsp for uncaoting step |
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What is the early endosome?
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A sorting and recycling center
-membrane is either recycled back to PM or goes to a late endosome |
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What is the Late endosome?
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Depository for ligands targeteed for degrradation.
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What are lysosomes for?
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hydrosases under pH 5.5 to break down.
Fuse with late endosomes |
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Which part of the endocytic process is dependend on a microtubule?
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Early endosome to late endosome transport
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What is recycled from the early endosome?
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1. Membrane material
2. Receptor proteins |
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What happens when insulin is in a receptor?
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The cell is stimpulated and a signal is sent to glucose receptors to go to plasma membrane. Boost glucose uptake
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Do lysosomes contain M-6-P?
Do late endosomes? |
No
es |
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What happens in Neiman Pick diseases?
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-e- late endosomal/lysosomal functions
- some sphingomyelinase deficiency lipid buildup in lysosome For Type A,b |
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What about Type C Nieman -Pick disorder?
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Mutation in NPC1 protein
Cholesterol accumulation in late endosome. Can't get away, and M6P doesnt get back to golgi |
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What is transcytosis?
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A polarized cell function
Important for nursing Fc receptor binds antibodies from intestinal lumen to EC fluid |
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What types of receptors are recycled when their ligands go to lysosomes?
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LDL-R and LDL
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When are receptors and ligands both recycled?
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apotransferrin, transferin-R
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When are receptors and ligands both delivered to lysosomes?
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epidermal growth factor, EGF-receptor
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When are receptor and ligand moved from one domain to the other (trancytosis)?
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maternal IgGs
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When are receptors recycled while the ligands are stored?
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vitelligenin in oocytes- very rare.
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What are caveolae?
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-non clathrin coated membrane structures.
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What is the coat protein of caveolae?
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caveolin
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What type of function do they have?
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non-clathrin pinocytosis
-small solute uptake - potocytosis cell signaling- enriched in cholesterol, adenylate cyclases -Very important |
