L19 - Wednesday,November10,2010...

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Wednesday, November 10, 2010 Secretory and Endocytic Pathways Reading: Chapter 15, pages 514 - 526  Objectives Translocation occurs  bidirectionally  into and out of the nucleus.  Proteins are imported from the cytosol into the nucleus. Examples include DNA  and RNA polymerases, histones, transcription factors, and ribosomal proteins. mRNA's and assembled ribosomal subunits are exported from the nucleus to the  cytosol. The nucleus is surrounded by a double membrane, which is perforated by  nuclear  pores . These pores are permeable to molecules of <  20,000 daltons. The pores  act as  regulated portals  for mRNA's and for larger proteins.  The Big Picture: eukaryotic organelles can be grouped into three categories. 1. The Nucleus   In a class by itself. 2. Mitochondria and Chloroplasts   Derived from endosymbiotic ancestors; still contain their own DNA. Proliferate like bacteria, by growth and division. Don't exchange membrane with other organelles. Composed primarily of unique components.
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3. The Endomembrane System: Endoplasmic Reticulum (ER), Golgi   Apparatus, Plasma Membrane, Endosomes, Lysosomes   Internal spaces are topologically equivalent to the outside of the  cell. Proliferation mechanism still a matter of debate.
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This note was uploaded on 02/09/2011 for the course BIOS 20182 taught by Professor Lahn during the Spring '11 term at UChicago.

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L19 - Wednesday,November10,2010...

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