Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Slides prepared by Stephen Gehnrich, Salisbury University 5 C H A P T E R Cellular Movement

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sponges (phylum Porifera) Cnidarians MedusaHydra Ctenophores Sea walnut Sea gooseberries

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Flatworms Nematodes Annelids Annelids – Internal structure

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Internal structure of a crayfish (lateral view).

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cytoskeleton and Motor Proteins  All physiological processes depend on movement  Intracellular transport  Changes in cell shape  Cell motility  Animal locomotion

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cytoskeleton and Motor Proteins  All movement is due to the same cellular “machinery”  Cytoskeleton  Protein-based intracellular network  Motor proteins  Enzymes that use energy from ATP to move

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Use of Cytoskeleton for Movement  Cytoskeleton elements  Microtubules  Microfilaments

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cytoskeleton “road” and motor protein carriers

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reorganizing the cytoskeletal network A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Motor proteins pull on the cytoskeletal “rope”

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cytoskeleton and Motor Protein Diversity Structural and functional diversity Multiple isoforms Various ways of organizing Alteration of function

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubules  Are tubelike polymers of the protein tubulin  Similar protein in diverse animal groups  Multiple isoforms  Are anchored at both ends  Microtubule-organization center (MTOC) (–) near the nucleus  Attached to integral proteins (+) in the plasma membrane

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Function of Microtubules  Motor proteins can transport subcellular components along microtubules  Motor proteins kinesin and dynein  For example, rapid change in skin color

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubules: Composition and Formation  Microtubules are polymers of the protein tubulin  Tubulin is a dimer of  -tubulin and  -tubulin  Tubulin forms spontaneously  For example, does not require an enzyme  Polarity  The two ends of the microtubule are different  Minus (–) end  Plus (+) end

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubule Assembly  Activation of tubulin monomers by GTP  Monomers join to form tubulin dimer  Dimers form a single-stranded protofilament  Many protofilaments form a sheet  Sheet rolls up to form a tubule  Dimers can be added or removed from the ends of the tubule  Asymmetrical growth  Growth is faster at + end  Cell regulates rates of growth and shrinkage

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubule Growth and Shrinkage Growth / Shrinkage Local [tubulin] Dynamic instability MAPs Temperature Chemicals (Taxol, Colchicine) GTP hydrolysis on b-tubulin STOPsKatanin

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubule Dynamics Figure 5.5

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regulation by MAPs Figure 5.6

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Movement Along Microtubules  Motor proteins move along microtubules  Direction is determined by polarity and the type of motor protein  Kinesin move in (+) direction  Dynein moves in (–) direction  Movement is fueled by hydrolysis of ATP  Rate of movement is determined by the ATPase domain of motor protein and regulatory proteins  Dynein is larger than kinesin and moves five times faster

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vesicle Traffic in a Neuron Figure 5.7

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cilia and Flagella  Cilia  numerous,  wavelike motion.  Flagella  single or in pairs,  whiplike movement.

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microtubules and Physiology Table 5.1

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microfilaments  Polymers composed of the protein actin  Found in all eukaryotic cells  Often use the motor protein myosin  Movement arises from  Actin polymerization  Sliding filaments using myosin  More common than movement by polymerization

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microfilament Structure and Growth  G-actin monomers polymerize to form a polymer called F-actin  Spontaneous growth  6–10 times faster at + end  Treadmilling  Assembly and disassembly occur simultaneously and overall length is constant  Capping proteins  Increase length by stabilizing – end and slowing disassembly

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microfilament (Actin) Arrangement  Arrangement of microfilaments in the cell  Tangled neworks  Microfilaments linked by filamin protein  Bundles  Cross-linked by fascin protein  Networks and bundles of microfilaments are attached to cell membrane by dystrophin protein  Maintain cell shape  Can be used for movement

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Microfilament (Actin) Arrangement Figure 5.10

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Movement by Actin Polymerization  Two types of amoeboid movement  Filapodia are rodlike extensions of cell membrane  Neural connections  Microvilli of digestive epithelia  Lamellapodia are sheetlike extensions of cell membrane  Leukocytes  Macrophages

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Actin Polymerization and Fertilization Figure 5.11

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Myosin  Most actin-based movements involve the motor protein myosin  Sliding filament model  17 classes of myosin (I– XVII)  Multiple isoforms in each class  All isoforms have a similar structure  Head (ATPase activity)  Tail (can bind to subcellular components)  Neck (regulation of ATPase)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sliding Filament Model  Myosin is an ATPase  Converts energy from ATP to mechanical energy Sliding Filament Model Chemical reaction Myosin binds to actin (cross-bridge) Structural change Myosin bends (power stroke)  Need ATP to release and reattach to actin  Absence of ATP causes rigor mortis  Myosin cannot release actin

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sliding Filament Model - Cross-bridge cycle Figure 5.13 Extension Cross-bridge formation Power stroke Release

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Actino-Myosin Activity Two factors affect movement  Unitary displacement  Distance myosin steps during each cross-bridge cycle  Depends on  Myosin neck length  Location of binding sites on actin  Helical structure of actin  Duty cycle  Cross-bridge time/cross-bridge cycle time  Typically ~0.5  Use of multiple myosin dimers to maintain contact

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Myosin Activity Figure 5.14

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Actin and Myosin Function Table 5.2