Lect7 - Vesicular Traffic: Late Secretory...

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Vesicular Traffic: Late Secretory Pathway/Exocytosis and Endocytosis 1 1. How do you degrade/recycle components: send to lysosome: generate materials to keep cell running 2. How do you secrete proteins (exocytosis), to allow the cell to ‘talk’ to the outside world? 3. How do you bring things into the cell (endocytosis), and process them appropriately? Allows import of ‘food’, reception of ‘signals’, also can change cell’s future interactions by changing cell-surface components. send the right things out, bring the right things in, and chew up anything that causes trouble…. Cell Biology - lecture 14 © Gross- all rights reserved.
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Lecture #13: Vesicular Traffic Late Secretory Pathway/Exocytosis and Endocytosis 2 2 1 3 F09 D103 Cell Biology lecture 13- copyright © Gross- all rights reserved.
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Send things out: transport through the Golgi In order to be transported to either a Lysosome or be secreted, proteins are first passed through the Golgi where they are modified and sorted 3 F09 D103 Cell Biology lecture 13- copyright © Gross- all rights reserved.
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functional compartmentalization of the Golgi • Preexisting sugars (Asparagine, or N-linked) can be modified in Golgi • New sugars can be added in an O-linked fashion (added to hydroxyl groups of serine or threonine side-chains) NOTE: processing occurs in a spatial as well as a biochemical sequence. 4 cis-Golgi : required for the generation of a lysosomal sorting signal (M6P) Plasma membrane : protection, interaction with neighboring cells Unlike ER, resident Golgi proteins all membrane-bound!! Cell Biology - lecture 14 © Gross- all rights reserved.
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What do all these sugar modifications do for proteins? Sorting signals (mannose-6-phosphate) Sugars/carbohydrates added glycoproteins, are resistant to proteolytic enzymes (‘armor’ for proteins in tough environments, like lysosome) (a sugar is a ‘simple’ carbohydrate, all have typical general formula CnH2nOn) Secreted glycoproteins and proteoglycans (e.g. extracellular matrix) have special properties, e.g. form mucus coat that protects lungs ( glycoprotein: protein with added carbohydrates; proteoglycan: special glycoprotein with even more carbs ) 5 Cell Biology - lecture 14 © Gross- all rights reserved.
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- Acidic organelles that contain a collection of degradative enzymes: nutrient production for the cell (sort of like a cell’s stomach) •Final degredation products (AA, sugars, lipids like cholesterol) exported to cytosol • Responsible for degrading certain polymers into monomeric subunits (Responsible for the turnover of 50-70% of cellular protein) • Lysosomal enzymes work efficiently only at acid pH values (safety—if escape, don’t chew up proteins in cytosol) • Transport pumps pump protons (H+) from the cytosol, acidifying the lumen IMPORTANCE OF LYSOSOME? Tay-Sachs disease: defect in lysosomal enzyme
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This note was uploaded on 12/13/2011 for the course BIOSCI d103 taught by Professor Staff during the Fall '11 term at UC Irvine.

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Lect7 - Vesicular Traffic: Late Secretory...

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