cell bio exam 5

cytoskeleton

network of protein filaments that extends throughout the cytoplasm; determines cell shape, organizes organelles and interior components, coordinates movement in the cell, facilitates movement in the cell, and provides structural support

types of filaments

intermediate filaments, microtubules, and actin filaments

intermediate filaments

IF; intermediate in diameter and very stretchy; forms a network throughout cytoplasm surrounding nucleus and extends towards the periphery

microtubules

MT; biggest and thickest; but hollow

actin filaments

aka microfilaments; smallest and most abundant in eukaryotes; associated with shape

plectin

help stabilize and reinforce connections between different cytoskeleton filaments

desmosomes

connect membranes of neighboring cells

tetramer

2 dimers wound together

keratin filaments

most diverse class and are found in every type of epithelial cell in the body; can mix and match to make lots of flavors

nucelar lamina

meshwork of lamin intermediate filament proteins that underlie the nuclear envelope

epidermolysis bullosa simplex

mutation in keratin genes; easily blister and rash

progeria

mutation in nuclear lamin genes; causes premature aging

tubulin

subunits of MTs

protofilament

tubulin dimers stack end to end through non-covalent interactions

beta end of MT

aka plus end; where tubulin dimers are usually added to a growing MT

alpha end of MT

aka minus end; where tubulin dimers are more likely to be lost

Centrosome

center of MT that regulate location, number and orientation of MT in animals

centrioles

pair surrounded by centrosomes; then surrounded by protein matrix

dynamic instability

sudden switching from polymerization to depolymerization

motor proteins

drive movement of vesicles and small organelles alpng cytoskeletal filaments

dynein

moves towards minus end

kinesin

moves towards plus end

cilia

hair like projections covered by plasma membrane and extend from surface of many eukaryotic cells

flagella

long projections that have similar internal structure of cilia, but designed to move entire cell

Protofilament

Row of microtubules

taxol

bind and stabilize MT

colchicine, colcemid and vinblastine, vincristine

bind tubulin dimers and prevents their polymerization

actin monomers

attatch end to end to form a strand

plus end of actin monomer

more likely to be where actin is added

minus end of actin monomer

more likely to be where actin is lost

Actin-ATP added

on plus end

Actin-ADP lost

on minus end

cytochalasin/ latrunculin

inhibit actin polymerization

Phalloidin

stabilizes actin filaments

thymosin/ profilin

actin monomer seuqestering proteins

formins/ actin-related proteins

actin nucelating protein

lamellipodia

sheet-like projections

filopodia

thin, stiff projections

actin-related proteins

promote formation of branched actin filaments

Rho-GTPase family proteins

pathways requiring changes in actin filament orientation; impact organization of actin filaments

myosins

actin-dependent motor proteins using ATP to provide E to move along actin filaments toward plus end

myosin 1

smaller, tail differs among types of myosin 1 allowing it to carry different cargos

myosin 2

longer, form as dimers with tails forming coiled-coil

myosin 2 filaments

myosin 2 dimers clustered; myosin heads point in opposite directions away from center

z-disc

actin plus ends attatched here; minus ends interact with myosin filaments

sarcomere

z disc to z disc

cell cycle

process by which cell duplicates it's contents then splits into 2

4 stages of cell cycle

1. M, 2. G1, 3. S, 4.G2

m stage of cell cycle

mitosis (division of chromosome) and cytokinesis (division of membrane

g1 stage of cell cycle

step 1; growth; part of interphase

s stage of cell cycle

synthesis; DNA is duplicated; part of interphase

g2 stage of cell cycle

last bits and pieces added and checks done; part of interphase

cell cycle control system

complex network of regulatory proteins that coordinates progression into each stage of cell cycle

what is used to switch cell cycle proteins on and off

phosphorylation

kinases in cell cycle

always present, but only active when bound to cyclin

kinases with cyclin bound are called

cyclin-dependent kinases

M cyclin

helps regulate G2 to M transition and forms a complex with M-Cdk

M-Cdk and M cyclin complex aka

maturation promoting factor

s cyclin binds to

S-Cdk; helps regulate G1 to S

G1/S cyclins bind to

G1/S Cdk; helps regulate G1 to S

anaphase-promoting complex

M and S cyclins are degraded by this by the addition of ubiquitin by APC

terminally differentiated cells

cells that stop dividing and differentiate

retinoblastoma protein

hold transcription factors in an inactive state; prevents transcription of cell proliferation genes

origin recognition complex (ORC)

sits on origins of replication; Cdc6 binds it

condensins

protein complexes that help each sister chromatid wind into a more compact piece of DNA

cohesins

sister chromatids held together by these; assmeble along length of paired sister chromatids

centrosome cycle

duplicating and separating centrosomes; duplicate in S/G2

aster

centrosomes separate and initiate a radial array of microtubules called

spindle poles

2 centrosomes

kinetochore

some microtubules grab chromosomes here; protein complex at centromere of each sister chromatid

metaphase

duplicated chromsomes attatched to mitotic spindle align halfway between poles

anaphase

sister chromatids separated by breaking of cohesins

separase

protease destroying cohesins

securin

holds inactive separase; targets degredation by APC

+ end of kinesin

embedded in the kinetochore and helps move the chromosome as it chews plus end

- end of kinesin

embedded at centrosome and reels in MT as it chews

anaphase B

spindle poles themselves move apart

cytokinesis

process by which the cytoplasm is cleaved in 2 and completes M phase

contractile ring

contains actin/myosin filaments that use the filament sliding mechanism to sever cytoplasm