cell bio section 2 outline

cell bio section 2 outline - The Biosynthetic-secretory and...

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The Biosynthetic-secretory and Endocytic Pathways: Every cell must: eat, communicate w/and respond to environment. To do this, it must adjust the composition of its plasma membrane in response to need. This diagram shows the compartments of eukaryotic cell involved in vesicular transport. The lumen of each membrane enclosed compartment it topologically equivalent to the outside of the cell. All compartments shown communicate w/one another and outside of cell by means of transport vesicles. The biosynthetic- secretory pathway (red arrows) is how protein molecules are delivered from the ER to the plasma membrane via or (via endosomes) to lysosomes. The endocytic pathway (green arrows) is how molecules are ingested by vesicles derived from plasma membrane and delivered to early endosomes and the (via late endosomes) to lysosomes. Blue arrows denote retrieval pathways for the backflow of selected components. Through exocytosis, the biosynthetic-secretory pathway delivers new proteins, carbs, and lipids to the plasma membrane or extracellular space. Through endocytosis plasma membrane components are removed and delivered to endosomes for recycling. Endocytosis also used to import nutrients Within a cell, “transport vesicles” continually bud off from one compartment and fuse with another carrying membrane components and soluble molecules called “cargo.” The flow of this traffic is highly organized, leading outward from ER toward gogli apparatus and cell surface, w/a side route leading to lysomes, while the endocytic pathway leads inward from plasma membrane. The flow of membrane b/w compartments is balanced Each transport vesicle that buds off from a compartment must be selective: must take up only the appropriate molecules, must fuse only w/the appropriate membrane. Molecules are synthesized, processed, stored and delivered in a series of controlled steps The contents of each compartment can be transported through different membrane-enclosed vesicles Outward flow: ER-> Golgi-> Cell exterior/lysosomes Inward flow: plasma membrane-> early endosomes-> late endosome Vesicles are selective and recycled The Membrane-enclosed Compartments : Vesicular transport mediates exchange of components b/w ten or more chemically distinct membrane enclosed compartments. How do compartments maintain a special identity? The composition of the enclosing membrane, including the molecular markers displayed on the cystolic surface acting as guidance cues for incoming traffic. How are markers kept at high [ ] on one compartment and low [ ] on another? Has to do with how patches of membrane, enriched or depleted of certain components, bud off from one compartment and transfer to another.
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Vesicles exchange cargos by budding off from donor membrane or fusing with target membrane: Transport vesicles bud off from one compartment and fuse with another. They carry cargo from the lumen and material from the membrane of the donor compartment, to the lumen and membrane of the target
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This note was uploaded on 03/20/2008 for the course CBIO 3400 taught by Professor Shen,kipreos during the Spring '08 term at UGA.

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cell bio section 2 outline - The Biosynthetic-secretory and...

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