Cytoskeleton, Cell Walls,

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Cytoskeleton, Cell Walls, ECM
Slide show modified fromhttp//www.explorebiolog
y.com
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Cytoskeleton network of fibers extending
throughout the cytoplasm
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• MICROTUBULES FUNCTION
• Structural support and cell movement
• Move chromosomes during cell division
• Centrioles spindle fibers
• tracks guide motor proteins
• Motor proteins dynein myosin
• cell motility
• Cilia flagella

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http//www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/
part1/movies/kinesin.dcr
MICROTUBULES Tracks guide motor proteins to
destination (Motor proteins dynein myosin)
ATP
SEE MOTORPROTEINS inACTION

• EXAMPLES
• Vesicles containing neurotransmitters migrate to
  tips of nerve cells
• Vesicles move to Golgi along cytoskeletal tracks
• Cytoplasmic streaming

http//python.rice.edu/kolomeisky/transport.htm
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Cilia and Flagella

• Are locomotor appendages
• Extensions of cytoskeleton
• Examples
• Many unicellular protists move with flagella
• Some plant reproductive cells have flagella
• Cilia in oviducts move egg toward uterus
• Cilia lining windpipe sweep mucous out of lungs
• Flagellum in sperm cells
• (Prokaryotic flagella dont have microtubules)

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• Cilia and flagella share a common ultrastructure

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FLAGELLUM (few, long) whip-like movement cell
moves in same direction as axis of flagellum
CILIUM (many, short) oar-like movement cell
moves perpendicular to axis of cilium
http//web.jjay.cuny.edu/acarpi/NSC/13-cells.htm
http//www.sk.lung.ca/content.cfm?edit_realwordhw
breathe
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• MICROFILAMENTS
• STRUCTURE
• Thinnest class of fibers
• Twisted double chain of actin subunits
• 7 nm in diameter
• FUNCTION
• Crosslinks with microtubules (cell shape)
• Muscle cells Actin filaments interact with
  myosin motor proteins to create muscle
  contraction
• Amoeboid movement
• Cytoplasmic streaming

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MICROFILAMENTS

• Make up contractile apparatus of muscle
• Contain the motor protein myosin in addition to
  actin

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• Amoeboid movement
• Actin filaments constantly form dissolve making
  cytoplasm liquid or stiff during movement

http//www.nextftp.com/jissen/ameba.gif
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• Cytoplasmic streaming
• Speeds distribution of materials

http//www.daviddarling.info/images/cytoplasmic_st
reaming.gif
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NUCLEAR LAMINA
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Cell Walls of Plants
Protection Maintain shape Also found in
Prokaryotes, fungi, and some protists Composition
varies with species/cell type Basic
design Microfibrils of polysaccharide
cellulose embedded in matrix of other
polysaccharides (like steel reinforced
concrete)
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Plant cell wall Structure PRIMARY CELL
WALL MIDDLE LAMELLA- between primary cell
walls of adjacent cells made of sticky
polysaccharides (pectins) glues cells
together SECONDARY CELL WALL built when cell
stops growing between plasma membrane and 1
cell wall
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Unify plant into one living continum
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• Types of intercellular junctions in animals

TIGHT JUNCTIONSMembranes of neighboring cells
and pressed together bound by proteins Forms
continuous seal to prevent leakage of
extracellular fluid across layer of
cells DESMOSOMES (anchoring junctions) Act like
rivets to fasten cells together into strong
sheets Intermediate proteins (keratin) anchor
desmosomes in cytoplasm GAP JUNCTIONS
(communicating junctions) Channels connect to
adjacent cells Special membrane proteins surround
pore Necessary for communication between cells in
heart muscle and animal embryos
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The Cell A Living Unit Greater Than the Sum of
Its Parts

• Cells rely on the integration of structures and
  organelles in order to function

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