2005-2006 AP Biology Chapter 7. The Cell: Cytoskeleton
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2005-2006AP Biology
Chapter 7.
The Cell:Cytoskeleton
2005-2006AP Biology
Cytoskeleton Function
structural support maintains shape of cell provides anchorage for organelles
motility cell locomotion cilia, flagella, etc.
regulation organizes structures &
activities of cell
2005-2006AP Biology
Cytoskeleton Structure
network of fibers extending throughoutcytoplasm
3 main protein fibers microtubules microfilaments intermediate filaments
It’s a matter of size…
2005-2006AP Biology
2005-2006AP Biology
Evolutionary perspective Proteins that make up the fibers are
very similar in all living things from bacteria to humans
tubulin (all cells) actin (eukaryote cells)
Means that they are bothancient and essentialfor life
2005-2006AP Biology
Microtubules Structure
thickest fibers hollow rods about 25nm
in diameter constructed of protein,
tubulin grow or shrink as more
tubulin molecules areadded or removed
2005-2006AP Biology
Microtubules Function
structural support & cell movement move chromosomes during cell division
centrioles tracks that guide motor proteins carrying
organelles to their destination motor proteins: myosin & dynein
motility cilia flagella
2005-2006AP Biology
Centrioles Cell division
in animal cells, pair of centriolesorganize microtubules guidingchromosomes in cell division
2005-2006AP Biology
Cilia & flagella Extensions of eukaryotic cytoskeleton Cilia = numerous & short (hair-like) Flagella = 1-2/cell & longer (whip-like)
move unicellular & small multicellularorganisms by propelling water past them
cilia sweep mucus & debris from lungs flagellum of sperm cells
2005-2006AP Biology
Cilia Oar-like movement
alternating power & recovery strokes generate force perpendicular to cilia’s
axis
2005-2006AP Biology
Flagella undulatory movement
force generated parallel to flagellum’saxis
2005-2006AP Biology
Cilia & Flagella Structure
remember 9+2! 9 pairs of
microtubulesaround 2 singlemicrotubules incenter
bending of cilia &flagella is drivenby motor protein dynein
requires ATP
2005-2006AP Biology
2005-2006AP Biology
Microfilaments (actin filaments) Structure
thinnest class of fibers solid rods of protein, actin twisted double chain of actin
subunits about 7nm in diameter
Function 3-D network inside cell membrane in muscle cells, actin filaments
interact with myosin filaments tocreate muscle contraction
2005-2006AP Biology
Microfilaments (actin filaments) Dynamic process
actin filaments constantly form &dissolve making the cytoplasm liquidor stiff during movement movement of Amoeba cytoplasmic streaming in plant cells
speeds distribution of materials
“Let’s go to the video tape!”(play movie here)
2005-2006AP Biology
Intermediate filaments Structure
specialized for bearing tension built from keratin proteins
same protein as hair intermediate in size 8-12nm
Function hold “things” in place inside cell more permanent fixtures of
cytoskeleton reinforce cell shape & fix
organelle location nucleus is held in place by a
network of intermediate filaments
2005-2006AP Biology
Summary Microtubules
thickest cell structure & cell motility tubulin
Microfilaments thinnest internal movements
within cell actin, myosin
Intermediate filaments intermediate more permanent fixtures keratin
• actin• microtubule• nuclei
2005-2006AP Biology
2005-2006AP Biology
2005-2006AP Biology
Cell Junctions
Where cells touch each other…
2005-2006AP Biology
Plant cell wall Structure
cellulose primary cell wall secondary cell wall middle lamella = sticky polysaccharides
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Intercellular junctions Plant cells
plasmodesmata channels allowing cytosol
to pass between cells
plasmodesmata
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Animal cell surface Extracellular matrix
collagen fibers in network ofglycoproteins support adhesion movement regulation
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Intercellular junctions in animals
2005-2006AP Biology
Intercellular junctions Animal cells
tight junctions membranes of adjacent cells fused forming
barrier between cells forces material through cell membrane
gap junctions communicating junctions allow cytoplasmic movement between
adjacent cells desmosomes
anchoring junctions fasten cells together in strong sheets
2005-2006AP Biology
2005-2006AP Biology
2005-2006AP Biology
A cell is a living unit greaterthan the sum of its parts
2005-2006AP Biology
And now for some…Stupid Penguin Tricks….
Any Questions??
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