Lesson 18: Cytoskeleton 1: Intermediate Filaments and Microtubules

cytoskeleton

the _______:
-gives the cell shape

-organizes components

-produces large-scale movements

3

cytoskeletal network has __ components:

-actin filaments

-microtubules

-intermediate filaments

noncovalent

cytoskeletal filament subunits are bound by ____ interactions

intermediate

Which filament is the strongest and most stable?

false

True or false: intermediate filaments are present in plants and fungi

structure

interm filaments provide cell ______ and tensile strength, withstand mechanical stress

keratins, lamins

Intermediate filament proteins:

1. cytoplasmic: ______ in epithelia

2. cytoplasmic: vimentin in connective tissue, muscle, and neuroglial

3. cytoplasmic: neurofilaments in nerve cells

4. nuclear: _______ in all animal cells

do not

Interm Filaments: NO POLARITY, tetramer is symmetric, (do/do not) bind to nucleotides

tumors

IF protein identification in biopsies using antibodies can pinpoint the orign of _____

desmosomes

Keratins link cells via attachment to ________

pore

lamins for a basket inside the nucleus around the nuclear _____

-also an attachment site for chromosomes during interphase

-depolymerize during mitosis so spindle can work

phosphorylated, dephosphorylated

lamins disassemble if _____ and assemble if ______

motor

IF vs. microtubules and actin

No polarity!

No nucleotide!

regulated by extrinsic factors (kinase/phosphatase)

No _____ proteins!

polarity

Microtubules in…

-Interphase cell: establish internal _______ to organize movement

-Dividing cell: chromosome segregation

-Ciliated cell: beat cilia and flagella to move

yes

Are microtubules polarized?

GTP

Microtubule structure:

1. tubulin packs w/ lateral and longitudinal contacts

2. become hollow cylinders, protofilaments pack together into tube

3. each tubulin binds to ___

randomly, catastrophe, rescue

Microtubule Dynamic Instability: total mass remains constant, but individual microtubules grow and shrink (randomly/coordinated)

______: more shrinking, _________: more growth

GDP

microtubule GTP cap at PLUS end (if hydrolyzed to ____ it will depolymerize)

length

Kymographs monitor ______ of microtubule over time

microtubule

the centrosome is the primary site for _________ nucleation

-centrioles recruit and scaffold the pericentriolar material (PCM)

-centrioles are made of a triplet of microtubules

gamma

centrosomes require ______ tubulin, acts as the seed for new microtubule nucleation

augmin

_________ recruits gamma tubulin ring complex to the side of a microtubule to nucleate another microtubule at a low angle

true

true or false: microtubule branching maintains polarity

microtubules

the mitotic spindle is made of…

microtubules

cilia/flagella are made of….

T, A

Tubulin vs. Actin (T or A):

__: heterodimer, GTP, residues supplied by longitudinal lattice, 13 protofilaments, dynamics at PLUS end

__: monomer, ATP, residues supplied by monomer, 2 protofilaments, grows at barbed PLUS end