intermediate filaments

actin filaments

microtubule filaments

non-covalent bonds

hydrophobic interactions

support cellular cytoplasm

intracellular transport

cell shape

motility

nuclear lamina

surrounding nucleus and extending to cell periphery

any that stretch (intermediate filaments have

high tensile strength)

muscle, GI, epithelial, etc

G actin - 'free' actin, globular, not in a filament

F actin - 'filamentous actin', assembled in filaments

muscle contraction

cleavage furrow formation

cell movement

the layer of cytoplasm just beneath the plasma membrane.  high in actin concentration

1) maintain cell shape

2) help in formation of cell surface extensions (ex microvilli)

tubulin dimers bound together in chains that make up microtubule walls

intracellular transport

anchoring intracellular organelles

form mitotic spindle

csome separation during cell division

the microtubule organizing center

microtubule associated proteins (MAPs)

microtubule stability

motor function

kinesin - moves toward + end

dynein - moves toward - end

motor head

cargo

tail

head domain/motor domain = 2 light chains

tail domain = 2 heavy chains, twisted together

muscle movement in vertebrates.

myosin molecules connect actin filaments, move in opp directions to pull filaments together.

myosin fibers along a sarcomere 'walk' along adjacent actin strands, pulling the 'z line' together

a functional unit of skeletal muscle.

thick filaments (mostly myosin)

thin filaments (mostly actin)

ATP attached to mysoin

1. hydrolysis to ADP causes conformationaly change to head region allowing it to bind actin

2. when ATP binds actin-bound myosin head get release from actin

3. repeat

when Ca is absent: tropomysin/tropin complex inhibits binding of actin and myosin

when Ca present: tropomysin/tropin complex released, allows movement 

1. neurotransmitter triggeres surface receptor on cell

2. sarcoplasmic reticulum releases Ca

3. Ca causes tropomysin/tropin complex to release from actin

4. ATP-ADP causes myosin to bind actin

5. ADP-ATP causes mysoin to release actin

6. Adjacent actin filaments pulled together

early Anaphase - small vessicles containing polysaccharides and glycoproteins needed to form cell wall travel from Golgi on microtubules via motor proteins and align along equatorial region of the spindle

protrusion

adhesion

contraction

lamellipodium.

myosin I pushes + end actin filaments against plasma membrane

integrins.

intracellular domain - connected to actin filaments

extracellular domain - connected to ECM

back of cell contracts, pushing rest forward.

myosin II may be involved

head - 2 globular heavy chains

tail - 2 light chains, twisted

(mysoin has light head, heavy tail)

ATP driven

kinesin - + end directed

dynein - - end directed

ATP

kinesisn + myosin I/II = plus end directed

dynein = neg end

kinesin - attachment (+ end)

dynein - separation (- end)

astral microtubules -face csome side of centrosome

polar microtubules - face pm side of centrosome

kinetochore microtubule - astral mctble that is attached to csome

centrosome end (-) - kinesin

kinetochore end (+) - dynein

extracellular signal proteins that bind surface receptors and cause intracellular signaling resulting in expression of genes needed for cell division

- in some cancer, growth factors are continually bound to their recpetors

S

G2

M

G1

migration of cancer cells.

1) adhesion to neighboring cells broken

2) migration via actin filaments to other parts of the body

Vinblastine - binds MTs, causes disassembly

Taxol - binds MTs, prevents disassembly

octagonal structure of repeating subunits

called nucleoporins with fibrils extending into cytoplasm and nycleus making up the nuclear cage

in = histones, nucleotides, helicase, transcription and replication enzymes

out = mRNA, ribosomes

1. beta importin binds alpha importin to form active transport protein

2. transport protein binds adaptor proteins attached to nuc localization signal on molecule.

3. importins bind FG repeats on nucleoporins

4. GTP associated w pore is cleaved changing pore shape and allowing transport across memb.

5. importins released

1. molecules have nuclear export signals

2. export signals bind nuc export receptors (soluble proteins)

3. export receptors bind nucleoporin

4. GTP cleaved to open pore

5. transported across

1. cytosollic (free) ribosome begins translation of mRNA

2. ER signal sequence on protein directs ribosome to ER

3. Signal recognition particle releases from ER, attaches to signal sequence

4. Translation is paused

5. SRP binds SRP receptor on ER surface

6. SRP releases, returns to ER membrane, translation resumes

7.  Peptide threaded through protein translocator/Sec61 pore protein

6 polypeptides w an RNA.

has pocket of methionines (flexible, multi-binding)

signal peptidase enzyme

signal sequence left in membrane

binding proteins

heat shock proteins

protect protein from misfolding

lower energy

protein synthesized on cytosollic ribosomes

signal sequence casues migration to organelle

protein imported

signal peptidase cleaves protein

(post translational import)