Cell Biology Exam 2

Cell Biology Exam 2 - Cell Biology Exam 2 Our Friend the...

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Cell Biology Exam 2 Our Friend the Nucleus: -Central Dogma of Molecular Biology *information moves in the cell such that -DNA Housed in the Nucleus *Replication and Transcription –require protein, yet, protein is made in the cytoplasm -Translation requires RNA as well as protein --Somehow the protein from the cytoplasm has to get into the nucleus and RNA in the nucleus has to get out of the nucleus and into the cytoplasm --Thus, nucleus must have specific mechanisms for controlling protein/RNA import/export - Roles of the Nucleus 1. House DNA and Processes dependent on DNA 2. Control Import and Export 3. Regulate gene expression 4. Sequesters things that are only needed in cytoplasm at particular times -Substructures that Comprise the Nucleus (anyone of these substructures are connected to the other one) 1. Nuclear Envelope 2. Nuclear Lamina 3. Nuclear Matrix 4. Chromatin 1. Nuclear Envelope -double membrane system -perforated by nuclear pores -boundary between nucleoplasm and cytoplasm -controls import/export -Appearance= highly irregular (thrown into folds) *often toroidal (donut shaped) which gives an increased Surface Area NUCLEUS DNA RNA Transcription CYTOPLASM PROTEIN Translation
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-Consequences of Shape *Low Magnitude *Intermediate Magnitude *High Magnitude Double Folds Membrane Nuclear Pore *Outer Nuclear Membrane: protein composition very similar to rough endoplasmic reticulum *Inner Nuclear Membrane: has very different protein composition than outer nuclear membrane *Nuclear Pores: -Both interesting and complicated -only known portal for movement into or out of nucleus **assume very complicated structures** -control of import/export is sophisticated and very efficient ** Structure of Nuclear Pore - each one of the sides is identical in structure to its neighbor -identity extends to its protein make-up ** Side View of Structure
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**Proteins that comprise nuclear pore complex --roughly 30 “nuclear porins” --NUP prefix -characterized by having repeated amino acid sequences “FG” repeats -FG – regulate how things move into/out of nucleus -several nuclear porins have been localized to particular pore subunits -Nuclear Pore Size --Top to Bottom: pore is approximately 120nm --Side to Side: pore is approximately 200nm -Cytoplasmic Fibrals- approximately 50nm long -How can we possibly distinguish between position of NUP 358,214, and 258 in a structure that is on 50nm? -Answer= Immunoelectron Microscopy -attach gold beads of different sizes to different antibodies 2. Nuclear Lamina -a 2D protein meshwork of proteins that underlies and is physically connected to the nuclear envelope Structure Function Cytoplasmic Fibrals Involved in protein import Outer Ring Subunits Responsible for anchoring cytoplasmic fibrils to columnar subunits Columnar Subunits Involved in import/export; act as scaffolding for other subunits Luminal Subunits Anchor columnar subunits to nuclear envelope; also act as diffusion barrier that
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This note was uploaded on 04/02/2008 for the course ZOO 570 taught by Professor Bement during the Fall '08 term at Wisconsin.

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Cell Biology Exam 2 - Cell Biology Exam 2 Our Friend the...

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