Dr. Koh Cytoskeleton FunSci 1

proteins

the cytoskeleton is a highly organized dynamic set of _ that provide support, shape, and scaffolding to the cell

tightly

formation and degradation of filaments are (tightly/loosely) regulated

actin filament (microfilament)

the smallest but more abundant filament, globular rod-shaped

intermediate filament

the second largest filament, rope-like structure

myotubules

the largest filament, hollow tube structure

actin filament

filament that gives gel-like consistency to the cytosol

a-actin

which isoform of actin is expressed in muscle cells and found in 4 human genes (important!!)

b and y-actin

which isoforms of actin are expressed in non-muscle cells and are very similar in structure

plasma membrane

where is actin mostly found in the cell (associated with cell movement)

globular actin (g-actin)

which type of actin is separated into two lobes by a deep cleft and contains ATPase activity

filament actin (f-actin)

which type of actin is a linear chain of G-actin and has functional polarity

polymerization

f actin is formed by ___ of G-actin

steady

when the concentration of G-actin = F-actin, we call this the state

actin-binding

the function of __ proteins is to cross-link actin filaments to form networks and bundles

F

actin-binding proteins provide a higher organization of ____ actin filaments

actin-binding proteins

fimbrin and filamin are examples of __

inhibits

thymosin B4 (stimulates/inhibits) actin assembly by competing for G-actin binding with filament

stimulates

profilin (stimulates/inhibits) actin polymerization by promoting exchange of ADP for ATP

capping

adding tropomodulin (-) and CapZ (+) to the ends of proteins to form stable ends is called _

filopodia

clotting factors reorganize actin into long projections called _

stop bleeding

after clotting factors rearrange actin into filopodia in platelets, the cell spreads and flattens to…

myosin

is an ATP-binding protein with am actin head and tail and functions in movement of motor proteins

treadmilling

movement of actin involving assembly (+ end) and disassembly (- end) is called __

sarcomere

a _ is the functional unit of skeletal muscle

troponin and tropomyosin

nerve impulse stimulates release of Ca2+, which binds to and _ to expose the myosin binding site on actin

extension

first step of cell locomotion: actin filaments cross link into bundles at the leading edge of the cell and actin polymerizes at the (+) end

adhesion

send step in cell locomotion: cell attaches to the substrate by focal adhesion

translocation

third step in cell locomotion: cell contents move forward by actin-cortico contractions

de-adhesion

fourth and final step in cell locomotion: retraction at the lagging edge, cell snaps forward

actin and spectrin

RBC shape is maintained by and

rigid

when mutate hemoglobin locks actin/spectrin binding, the RBC becomes _

cancer

anti-actin drugs may have a role in treating by destroying the cell's ability to metastasize

a-tubulin

which form of tubulin irreversibly binds GTP

B-tubulin

which form of tubulin reversibly binds GTP/GDP

heterodimer

a-tubulin and B-tubulin comine to form a

microtubule organizing center

any structure used by cells to nucleate or organize microtubules

disassembly

_ of microtubules causes the ends to become frayed (like jeans in a washing machine)

more

microtubules are (more/less) dynamic than actin

stable

cilia, flagella, and axons are (stable/unstable) forms of microtubules

unstable

mitotic cells are (stable/unstable) forms of microtubules

GTP

microtubule stability is controlled by concentration of _-tubulin

microtubule associated proteins (MAP)

MAP1, MAP2, MAP4, and Tau are __ that prevent microtubule disassembly by binding to the outer wall of filaments

katanin

_ is a de-stabilizing microtubule associated protein that breaks the linkage between subunits

microtubules

play an essential role in supporting cell movements during mitosis

trafficking

microtubules are essential for _ of proteins, vesicles, and organelles

kinesin

what is this microtubule protein?

dyenin

what is this microtubule protein?

cilia and flagella

the force generating mechanism in and _ is due to the microtubule protein dynein

proliferation

microtubules can be targeted in rapidly growing cancer cells during chemotherapy to block __

tau

Alzheimer's is characterized by neurofibrillary tangles, which occur when the MAP _ loses its binding affinity

intermediate filaments

this type of filament is important in cells subjected to stress (epithelial and muscle cells)

motility/contraction

unlike actin filaments and microtubules, intermediate filaments are only structural and don't contribute to ___

lamin

which subunit of intermediates filaments is the most abundant and provides structural support for the nucleus

keratin

which subunit of intermediates filaments is expressed in epithelial cells (hard tissues - hair, skin, nails)

vimentin

which subunit of intermediates filaments supports the cell membrane of leukocytes and endothelial cells

desmin

which subunit of intermediates filaments stabilizes sarcomeres in muscle cells

neurofilaments

which subunit of intermediates filaments influences radius of neuronal axons (proportional to nerve conduction speed)

intermediate filaments

which type of filament can be used as a diagnostic cell origin marker?