Micro - Cytoskeleton 8/14

Question 1

Microtubules

Answer 1

tubulin heterodimers - alpha/beta tubulin
Hollow cylinders
gamma tubulin - helps nucleate (found in centrosome/MTOC)

Question 2

MT properties

Answer 2

highly dynamic
polarized - + end is more dynamic
- end is in the MTOC

Question 3

MT functions

Answer 3

Mitotic spindle
railways
Cell shape
Cilia, flagella
centiroles, basal bodies

Question 4

MT instability and growth

Answer 4

Dynamic instability
Alpha/Beta GTP - assemble
GTP hydrolysis happens after time

Question 5

MT catastrophe

Answer 5

cycle of growth ends and disassembly begins

GDP dimers dissociates

Question 6

MT Rescue

Answer 6

When shrinkage stops and growth starts

Question 7

Taxol

Answer 7

stabilizes MTs

Question 8

Colchicines

Answer 8

prevent tubulin polymerization

Question 9

vinblastine

Answer 9

depolymerize MTs

Question 10

Kinesin

Answer 10

+ end on MT

Question 11

Dynein

Answer 11

• end on MT

Question 12

MT motor protein structure

Answer 12

Head binds to MT - determines direction
Tail/base - binds cargo
Use ATP to move

Question 13

MAPs for MTs

Answer 13

Tau
organize MTs into bundles or irregular meshworks
regulative stability

Question 14

MT nucleation and polymerization

Answer 14

Nucleation only happens at centrosome and takes a long time
Polymerization is rapid
y-tubulin required for nucleation but is not incorporated

Question 15

MT in cell division

Answer 15

Centrioles replicate
Types
Astral - radiate to cortex
Kinetochore - bind to chromosome
Polar - mix with opposing MTs

Question 16

Cilia/flagella

Answer 16

Both generate movement
Grow from a basal body (9 triplets MT)
Axoneme - core with 9+2 MTs
Ciliary dynein generates sliding force and beating

Question 17

Immotile Cilia Syndrome

Answer 17

results in obstructive lung disease, sterile males

Question 18

Kartagener’s Syndrome

Answer 18

combo of immotile cilia + situs inversus

Cilia normally establish the axis

Question 19

POlycystic kidney disease PKD

Answer 19

kidney failure due to numerous cysts from epithelium of kidney tubules
Loss of functional cilia

Question 20

Bardet-Beidl syndrome

Answer 20

Blindness due to loss of photoreceptors of retina

Cilia/basal bodies

Question 21

Spastic paraplegia

Answer 21

MT severing protein leads to spinal cord degenerative diseases

Question 22

Cancer therapies

Answer 22

Taxol - overstabilize MTs

Question 23

Actin composition

Answer 23

Nonhollow polymers of G actin

Helical

Question 24

Actin properties

Answer 24

Very highly dynamic
Can have different shapes/forms
Substrate for myosin motor proteins
Do not form organizing centers

Question 25

Actin nucleation

Answer 25

can happen anywhere Arp2/3 complex - branched filaments Formins - produce bundles of parallel unbranched filaments

Question 26

Actin polarization

Answer 26

Barbed + end - highly dynamic Pointed - end - more stable Myosins move towards the barbed end

Question 27

Actin functions

Answer 27

attach cytoskeleton to plasma membrane contractile ring for cleavage furrow cell motility short-range organelle transport

Question 28

Actin filaments

Answer 28

Helical Alpha, beta, gamma Alpha - muscle only Beta, gamma - all cells

Question 29

Actin polymerization

Answer 29

``` ATP dependent (GTP for MTs) After addition the ATP is gradually hydrolyzed G actin monomers --> F actin polymer Nucleation is slow, elongation fast Arp2/3, formins ```

Question 30

Acting Binding Proteins

Answer 30

sequester actin molecules, capping, cross linking actin, severing, annealing

Question 31

Actin stress fiber

Answer 31

bundle of many actin filaments in parallel (formin) Myosin - contraction Alpha-actinin - stabilizes bundles

Question 32

Leading edge

Answer 32

Arp2/3 makes filaments that start to push out and extend the filopodia

Question 33

Actin Myosins

Answer 33

Use energy from ATP hydrolysis to move Move toward barbed + end Undergo conformational change that results in force generation

Question 34

Microvilli

Answer 34

Actin based structure - increase surface area or detect sound Bundle of actin as core Myosin link the actin to the plasma membrane

Question 35

Fimbrin/villin

Answer 35

proteins that cross link the actin filaments in the microvilli Myosin I attach the central bundle to membrane for movement

Question 36

Terminal web

Answer 36

Bottom of microvilli | Actin and intermediate filaments

Question 37

Stereocilia

Answer 37

long microvilli - actin based

Question 38

Hereditary spherocytdosis

Answer 38

deforms red cells to fragile spherocytes due to mutations in spectrin

Question 39

RBC cytoskeleton

Answer 39

shape is determined by cytoskeleton | Network of spectrin molecules joined by protein complexis

Question 40

Intermediate filaments

Answer 40

non-polarized non-dynamic diverse Most structural role

Question 41

IF Functions

Answer 41

space filling tensile strength can have specialized functions desomosomes and hemidesmosomes

Question 42

IF structure

Answer 42

two monomers form a coiled-coil dimer 2 dimers in antiparallel = tetramers tetramers --> staggered pattern NO ATP/GTP needed

Question 43

Type I: Acid Keratins

Answer 43

IF | epithelial cells, nails, hair, diverse

Question 44

Type II: Neutral/basic keratins

Answer 44

IF | epithelial cells, nails, hair, diverse

Question 45

Type III IF

Answer 45

Vimentin - fibroblasts Desmin - muscle cells GFAP - glial cells

Question 46

Type IV IF

Answer 46

Neurons

Question 47

Type V Nuclear Lamins A/B/C

Answer 47

nuclear lamina of all nucleated cells

Question 48

Progeria

Answer 48

IF disease | Fast aging disease of lamina proteins (lamin A)