AP Biology

2005-2006

Chapter 7. The Cell:

Cytoskeleton

AP Biology

2005-2006

Cytoskeleton Function

u structural support maintains shape of cell provides anchorage for organelles

u motility cell locomotion cilia, flagella, etc.

u regulation organizes structures &

activities of cell

AP Biology

2005-2006

Cytoskeleton Structure

u network of fibers extending throughout cytoplasm

u 3 main protein fibers microtubules microfilaments intermediate filaments

Its a matter of size

AP Biology

2005-2006

AP Biology

2005-2006

Evolutionary perspective Proteins that make up the fibers are

very similar in all living things u from bacteria to humans

tubulin (all cells) actin (eukaryote cells)

Means that they are both ancient and essential for life

AP Biology

2005-2006

Microtubules Structure

u thickest fibers u hollow rods about 25nm

in diameter u constructed of protein,

tubulin u grow or shrink as more

tubulin molecules are added or removed

AP Biology

2005-2006

Microtubules Function

u structural support & cell movement move chromosomes during cell division

w centrioles tracks that guide motor proteins carrying

organelles to their destination w motor proteins: myosin & dynein

motility w cilia w flagella

AP Biology

2005-2006

Centrioles Cell division

u in animal cells, pair of centrioles organize microtubules guiding chromosomes in cell division

AP Biology

2005-2006

Cilia & flagella Extensions of eukaryotic cytoskeleton Cilia = numerous & short (hair-like) Flagella = 1-2/cell & longer (whip-like)

u move unicellular & small multicellular organisms by propelling water past them

u cilia sweep mucus & debris from lungs u flagellum of sperm cells

AP Biology

2005-2006

Cilia Oar-like movement

u alternating power & recovery strokes u generate force perpendicular to cilias

axis

AP Biology

2005-2006

Flagella undulatory movement

u force generated parallel to flagellums axis

AP Biology

2005-2006

Cilia & Flagella Structure

u remember 9+2! u 9 pairs of

microtubules around 2 single microtubules in center

u bending of cilia & flagella is driven by motor protein dynein

requires ATP

AP Biology

2005-2006

AP Biology

2005-2006

Microfilaments (actin filaments) Structure

u thinnest class of fibers u solid rods of protein, actin u twisted double chain of actin

subunits u about 7nm in diameter

Function u 3-D network inside cell membrane u in muscle cells, actin filaments

interact with myosin filaments to create muscle contraction

AP Biology

2005-2006

Microfilaments (actin filaments) Dynamic process

u actin filaments constantly form & dissolve making the cytoplasm liquid or stiff during movement movement of Amoeba cytoplasmic streaming in plant cells

w speeds distribution of materials

Lets go to the video tape! (play movie here)

AP Biology

2005-2006

Intermediate filaments Structure

u specialized for bearing tension u built from keratin proteins

same protein as hair u intermediate in size 8-12nm

Function u hold things in place inside cell u more permanent fixtures of

cytoskeleton u reinforce cell shape & fix

organelle location nucleus is held in place by a

network of intermediate filaments

AP Biology

2005-2006

Summary Microtubules

u thickest u cell structure & cell motility u tubulin

Microfilaments u thinnest u internal movements

within cell u actin, myosin

Intermediate filaments u intermediate u more permanent fixtures u keratin

actin microtubule nuclei

AP Biology

2005-2006

AP Biology

2005-2006

AP Biology

2005-2006

Cell Junctions

Where cells touch each other

AP Biology

2005-2006

Plant cell wall Structure

u cellulose u primary cell wall u secondary cell wall u middle lamella = sticky polysaccharides

AP Biology

2005-2006

Intercellular junctions Plant cells

u plasmodesmata channels allowing cytosol

to pass between cells

plasmodesmata

AP Biology

2005-2006

Animal cell surface Extracellular matrix

u collagen fibers in network of glycoproteins support adhesion movement regulation

AP Biology

2005-2006

Intercellular junctions in animals

AP Biology

2005-2006

Intercellular junctions Animal cells

u tight junctions membranes of adjacent cells fused forming

barrier between cells forces material through cell membrane

u gap junctions communicating junctions allow cytoplasmic movement between

adjacent cells u desmosomes

anchoring junctions fasten cells together in strong sheets

AP Biology

2005-2006

AP Biology

2005-2006

AP Biology

2005-2006

A cell is a living unit greater

than the sum of its parts

AP Biology

2005-2006

And now for some Stupid Penguin Tricks.

Any Questions??