Cell book notes TEST III

Cell book notes TEST III - Intracellular compartments and...

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Intracellular compartments and protein sorting 10/15 notes over pgs. 749-775 Intracellular vesicular traffic: Exocytosis : biosynthetic-secretory pathway delivers newly synthesized proteins, carbohydrates, and lipids to either the plasma membrane or to the extracellular space. Endocytosis : cells remove plasma membrane components and deliver them to internal compartment called endosomes. Cells also use endocytosis to capture important nutrients, lipids, cholesterol, and iron--- Lumen : interior space of each membrane-enclosed compartment Vesicles : membrane- enclosed spherical containers in which proteins are transported (selective) Cargo : membrane components and soluble molecules enclosed in a transport vesicle There are various types of coated vesicles:
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Coated vesicles: have a distinctive cage of proteins covering their cytosolic surface------ before vesicle fuse with a target membrane this coat/cage is discarded. There are two main functions of the coat- o It concentrates specific membrane proteins in a specialized patch---giving rise to the vesicle membrane-----therefore selecting molecules for transport. o The coat shapes the vesicle. There are 3 types of coated vesicles ( distinguished by their coat proteins) 1. Clathrin-coated: mediate transport from the Golgi apparatus and from the plasma membrane 2. COPI-coated: most commonly mediate transport from the ER and from the Golgi cisternae. COPI-coated proteins bud from the Golgi compartments 3. COPII-coated: transport material early in the secretory pathway and bud from the ER The Assembly of a Clathrin Coat Drives Vesicle Formation: Clathrin-coated vesicles: transport material from the plasma membrane and between endosomal and Golgi compartments. o The major protein component of clathrin-coated vesicles is clathrin itself. Each clathrin subunit consists of three large and three small polypeptide chains that form a triskelion. The clathrin triskelions determine the geometry of the clathrin cage. Adaptor proteins: major component of the Clathrin-coated vesicles that form a discrete second layer of the coat positioned between the clathrin cage and the membrane. o Adaptor proteins bind the clathrin coat to the membrane and trap various transmembrane proteins including transmembrane receptors (cargo receptors) Phosphoinositides Mark organelles and Membrane Domains: Inositol phospholipids usually comprise less than 10% of the total membrane phospholipids---but have important regulatory functions o Inositol phospholipids can undergo rapid cycles of phosphorylation and dephosphorylation at the3’, 4’, and 5’ positions of their inositol sugar head groups to produce various types of Phosphoinositides (PIPS).
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The distribution of PIPS varies from organelle to organelle and often within a continuous membrane from one region to another------Thereby (PIPS) define specialized membrane domains Local control of PI (phosphatidylinositol), PIP kinases and PIP phosphatases
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This note was uploaded on 02/09/2011 for the course BIOL 320 taught by Professor Bennet during the Spring '11 term at Indiana.

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Cell book notes TEST III - Intracellular compartments and...

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