AP Biology

CYTOSKELETON

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Cells gotta work to live! What jobs do cells have to do?

make proteins

proteins control every

cell function

make energy

for daily life

for growth

make more cells

growth

repair

renewal

AP Biology 2013-2014

Making New Cells

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Cytoskeleton Function

structural support maintains shape of cell

provides anchorage for organelles

protein fibers

microfilaments, intermediate filaments, microtubules

motility cell locomotion

cilia, flagella, etc.

regulation

organizes structures

& activities of cell

3 kinds of protein filaments

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Microtubules, Microfilaments &

Intermediate Filaments

Summarize in a table.

http://www.youtube.com/watch?v=TnDeITPGQjk

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Cytoskeleton

Intermediate Filaments: interwoven, rope-strands

built from a family of proteins

called keratins.

Function: Strength, maintain shape, fix organelle location.

Microtubules: tubes composed of

spiraling tubulin in two-part subunits. Function: shape & support

chromosome movement (centriole, spindle fibers)

movement of organelles (serve as tracks)

movement of cellular appendages (cilia, flagella)

“highways” along which the organelles travel Microtubule roads are dynamic. Assembled at one end

while being disassembled at the other.

Microfilaments: twisted double chain of actin subunits

Function: to bear tension,

resists pulling tensions within cell

(prevents cell from collapsing)

motility (cell movement) and shape,

and simply holding the cell together.

http://www.studiodaily.com/main/searchlist/6850.html

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microfilaments

Intermediate

filaments

microtubules

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microfilament (actin)

microtubule (tubulin)

nuclei

Cytoskeleton

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Cytoskeleton

Intermediate filaments

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http://sites.sinauer.com/cooper5e/animatio

n1203.html

http://www.dnatube.com/video/4216/How-

kinesin-walks-over-microtubules

http://vimeo.com/45238275

Motors:

kinesins &

dyneins

Microtubules Subunit is heterodimer

of a and b tubulin

http://www.dnatube.com/video/5002/Microtubules-Video

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Centrioles Cell division

in animal cells, a pair of centrioles organize microtubules

spindle fibers

Microtubules guide chromosomes in mitosis and keep the cell from collapsing

http://www.youtube.com/watch?v=VGV3fv-uZYI

NOT IN PLANT CELLS

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Centrioles Organization and movement

of chromosomes

} motors

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Centrosomes & Cancer Cancer cells often are aneuploid (have abnormal numbers

of chromosomes) role of centrosomes?

Chromosome movement in mitosis also involves

polymerization and depolymerization of microtubules.

Vincristine (found in the Madagascar periwinkle - a wildflower)

binds to tubulin dimers

prevents the assembly of microtubules

halts cells in metaphase of mitosis

How would you design

a chemotherapy drug?

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Anticancer Drugs Often target microtubules

Taxol® (found in the bark of

the Pacific yew)

-prevents depolymerization of

microtubules of the spindle

fiber

stops chromosome

movement

prevents the completion of

mitosis.

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Centriole Structure 9 sets of triplets,

no central doublet

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Basal Bodies modified centrioles that give rise to

cilia and flagella

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Cilia & Flagella – composed of microtubules “9 + 2” tubulin pattern

(9 outer doublets, 2 microtubules in center)

http://programs.northlandcollege.edu/biolo

gy/biology1111/animations/flagellum.html

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Movement Cilia & Flagella differ in their beating patterns.

http://programs.northlandcollege.edu/biolo

gy/biology1111/animations/flagellum.swf

“rowing” “whipping”

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Microfilaments

http://www.youtube.com/watch?v=Ch3izZOUjDs

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Intermediate Filaments

primary role:

to provide physical strength

to cells and tissues

http://iknow.net/player_window.html?url=media/cytoskeleton_au

to.swf&width=360&height=159

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http://www.youtube.com/watch?v=-bDg4gMYpsI&feature=related

Summary

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Cell Wall Maintains shape and size of plant cell;

prevents enlargement.

Animal cells lack a cell wall,

but have cytoskeleton and…

Plays important roles in the absorption,

transport and secretion of substances.

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Extracellular Matrix (ECM)

adhesion

movement

regulation

support

Major components: glycoproteins secreted by the cells;

Collagen – most abundant glycoprotein in ECM

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Extracellular Matrix Connects intra- and extra-cellular environments

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ECM

Lots of

interactions

involved

Pathways shown for

illustration purposes

only.

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ECM

Many processes

You should know that ECM

involves a set of proteins

called integrins, connects

intra- and extracellular

environments and is

essential to normal cell

function.

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Integrin activation Inactive integrin (red, blue); talin (yellow):

when talin binds (intracellularly),

integrin becomes active & interacts extracellularly with ecm.

http://multimedia.mcb.harvard.edu/flash/extravas

ation.swf

http://www.dnatube.com/video/551/The-

Inner-Life-Of-A-Cell-HQ

Start at 2:42

You do not need to know about integrin activation.

I’ve included it here only because you saw it in the cell video.

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Integrins

Again, proteins

are involved in

interactions.

(You do not need

to know the

details in this

slide.)

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The Cell http://www.dnatube.com/video/551/The-Inner-Life-Of-A-Cell-HQ