Презентация на тему The Cytoskeleton: Intermediate Filaments and Microtubules

filaments plus many filament-associated
proteins including molecular motors
Microfilaments

– composed of actin, these
filaments form dynamic networks that form
the basis for cell shape and movement

Microtubules – composed of tubulin, these
tubules act as tracks on which to move
vesicles and organelles. They also form the
basis of cilia and flagella. They are dynamic.

Intermediate filaments – composed of proteins
that associate to form rope-like structures
that are of high mechanical strength. They
position organelles and form a strong, long
lasting cell superstructure.

– INTERMEDIATE FIL.
ACTIN – STRESS FIBERS
ACTININ – STRESS FIBERS
VIMENTIN

– INTERMEDIATE

TUBULIN - MICROTUBULES

Cytoskeletal
Networks
Containing
Fluorescent
Proteins

Fluorescence
Microscopy allows
Visualization
Of cytoskeletal
Networks

Desmosomes
to hold
neighboring
cells
together.

is a coiled-coil
dimer. These
fibers are symmetric

by a network of intermediate
filaments called lamins. They serve

as
an anchoring site for chromosomes as
well as for intermediate filament networks
that extend from the nucleus out into the
cytoplasm.

and insert into plasma membrane junctions called desmosomes. Desmosomes

connect the intermediate filaments networks of neighboring cells forming a strong mechanical bond that keeps the cells from being pulled apart.

cell.
Example: nerve axons contain numerous micro-
tubules along their length.

If disrupted the axon
shrivels.

2. To provide “tracks” on which to move
vesicles carrying cargo.
Example: pigment granules move outward
and inward from cell center using microtubules.

3. To form the mitotic spindle which separates
chromosomes during mitosis and meiosis.

To form flagella and cilia – whip like
structures that propel cells.

dried
And platinum
Shadowed

minus ends. Centrosomes and
Microtubule organizing centers (MTOCs) cap

the
minus end; special membrane-associated proteins
cap the plus end.

“protein cloud”. Minus ends of microtubules are capped by

gamma tubulin rings and the centrosome serves as a microtubule organizing center (MTOC).

hydrolysis; GTP-
tubulin is required for
polymerization;

But after hydrolysis,
GDP-tubulin
favors depolymerization

plus end stops or is slow; but
the microtubule

starts to grow at this end again.

tyrosylation do too.

existing mts; cholchicine
destabilizes microtubules by monomer binding

their heads acting as “motors”

this process chemical energy is
transformed into mechanical energy, hence

the name motor protein.

A CONFORMATIONAL CYCLE THAT HYDROLYZES ATP

granules on MTs

a
neighboring
MT doublet