Lecture 2.2 Notes
Lecture 2.2 Notes 150.0
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This 5 page Class Notes was uploaded by Caroline Hess on Thursday October 22, 2015. The Class Notes belongs to 150.0 at University of Pittsburgh taught by McGreevy,Erica Margaret in Fall 2015. Since its upload, it has received 39 views. For similar materials see FOUNDATIONS OF BIOLOGY 1 in Biological Sciences at University of Pittsburgh.
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Date Created: 10/22/15
Lecture 22 The Actin Cytoskeleton Cells are highly organized 0 Everything has a speci c place 0 The cytoskeleton is comprised of lamentous proteins that determine cellular architecture 0 Microtubules o Actin Cytoskeleton determines cellular architecture 0 Maintains shape of the cell Constantly changing o Motility o Adhegon o Intracellular organization 0 Cell division 0 Three networks of lamentous proteins comprise the eukaryotic skeleton o Micro laments Smallest diameter Polymer made of protein actin Underlie plasma membrane 0 Intermediate Filaments Intermediate diameter Polymer made of various proteins Depends on cell type 0 Microtubules Large diameter Polymer made of proteins 0c and Btubulin Cytoskeletal laments re long chains of repeating protein subun s o A monomer is a repeating singleprotein subunit 0 A heterodimer is a repeating subunit of more than one protein Actin Actin laments are helical 0 Two strings of actin monomers twisted together Actin laments are polar 0 Have plus and minus ends Has nothing to do with charge Formed by polymerization of monomers o Actin laments grow from the plus end and shrink from the minus end Plus gt Minus Polymerization add monomers at plus end Depolymerization subtract monomers at minus end Globular Gactin and lamentous Factin are continuously interconverting Gactin Factin a 000 m 3 3 39 0 3 E t F 0 Individual Subunits Filamentous Subunits o If you put Gactin in test tube it would polymerize to F actin until it reached an equilibrium 0 Always a population of both Gactin and Factin 0 Cells can regulate polymerizationdepolymerization To change architecture 0 Bonds between monomers are noncovalent Easier to break Actin forms different types of networks for different purposes 0 Contractile bundle Gellike network 0 Tight parallel bundle Tight parae bundles are used to sense the environment 0 Uses biochemical signals Gellike networks extend the plasma membrane 0 Facilitates cell crawling 0 Found in highlymobile cels Accessory Proteins The organization of Factin is controlled by proteins that bind Gactin and Factin o Accessory Proteins Regulate spatial distribution and dynamic behavior of laments Determine site of assembly of new laments Destroy existing laments Regulate how many laments form 0 Link laments to each other or other cell structures such as organelles Actin bundling proteins link Factin into parallel bundles O Mari 0833c 8 oo 86 Do ngoooooiiif39 Motor Proteins Often associated with cytoskeletal elements Bind speci c lament types and use them as tracks 0 Use ATP to move along laments Typically move in one direction Myosin 0 Motor proteins that use ATP to move along actin laments Allows directional transport of substances across the cell 0 Most move towards plusend of actin 0 Has head and tail Head hydrolyzes ATP 0 Energy created from hydrolyzing ATP is used to move the head down the actin lament Once phosphorous is released the head resets Tail can attach to organelle or cargo Carries the cargo along the actin track Actin Filaments Actin laments can form antiparallel bundles that along with myosin motors allow contraction 0 Found in striated muscle Antiparale myosin laments contract actin networks 0 Muscle cells are comprised of repeating units of contractile actin and myosin laments Nonmuscle myosin contract actin networks are found in many other cell types 0 Example endotheia cells 0 An additional role for actinmyosin contraction is cytokinesis in all animal cells o It forms the contractile ring that splits the cell in two