lecture 4

Question 1

major functions of cytoskeleton

Answer 1

• network of protein filements
• highly dynamic
• structural support
• internal organization
• cell division
• large scale movementsm

Question 2

microscopy techniques to look at the cytoskeleton

Answer 2

light microscope, fluroescence microscope, transmission electron microscope

Question 3

immunofluorescence microscopy

Answer 3

-used to determine location of proteins within cell
- not live imagin gbecause cells are fixed
- primary antibody used to bind specidic protein of interest
- secondary antibody bunds to the primary antibody it is covalently tagged to a lfuorescen marker

• they are used toe xcite fluorescent market and visualize light emitted

Question 4

intermediate filaments

Answer 4

• involved in structural support

cytoplasmic IF
- in animal cells subjected to mechanical stress
- provides mechanical strength

nuclear IFs
- nuclear lamina

conserved alpha-helix central rod domain
N and C terminal domains differ

they are packed together like rope filaments

2 monomers> coiled-coil dimer

2 dimers> staggered antiparallel tetramer

8 tetramers associated side by sude and assembe into filament
most interactions are noncovalent

no filament polarity

Question 5

microtubules

Answer 5

-organizing function in all eukaryotes
- involved in cell organization, mitosis, structural support
- made of tubulin

• long hollow tubes
• made of individual subunits of two closely related globular proteins

-13 parallel protofiliments make up a hollow tube

can be stabilized to prevent disasseble

Question 6

microtubule protofilaments

Answer 6

• 13 parallel protofilimanet make up a hollow tubee
• bonds are non covalent

Question 7

invitro microtubule

Answer 7

• faster growth at plus end

Question 8

dynamic instability

Answer 8

plus ends of microtubules grow and shrink
needed for remodling
β-tubulin GTP → hydrolyzed to GDP

GTP cap: straight filaments, stronger binding

GTP hydrolysis, small conformatiional change, weaker binding

Question 9

dynamic instability: growing

Answer 9

Free αβ-tubulin dimers - bound to GTP, added to growing microtubules at plus end

shortly after dimer is added

rapid addition of αβ-tubulin dimers

Question 10

dynamic instability: shrinking

Answer 10

same as growing but there is a slower additon of αβ-tubulin dimers

Question 11

Microtubule Organizing Centers (MTOCs)

Answer 11

have nucleating sited for microtubule growth

Question 12

kinesins

Answer 12

generally moves towards plus end of microtubules

Question 13

dyneins

Answer 13

moves towards minus end of microtubules

Question 14

actin filaments

Answer 14

also known as microfilaments, present in all eukaryotes

made of, actin monomers, flexible

Question 15

structure of actin filaments

Answer 15

helical filament
- composed of a singular type of glibular protein
- two protofilaments twisted in a right handed helix

polarity
- plus end is different than minus end
- always saem orientation
-growth is faster on plus side

Question 16

actimn monomers

Answer 16

-free monomers are bound to ATP, bound to center of protein

• actin hysdrolyzes ATP to ADP, reduses strendth of binding between monomers in filament

Question 17

actin filament treadmilling

Answer 17

actin filament groth
- plus ATP-acyin, plus end addition, poliizeragtion, hydroolyzes ATP>ADP
- minus ADP-actin, loss of monomers

treadmilling
- actin filemytns remail the same size ans look stable
but they are continuously exchanging monomers at ends
need a continous supply of ATP

Question 18

myosins

Answer 18

• move towards plys end of actin filaments
• walking dudes
• use ATP hydrolysis for movement

myosin 1
- tail domain binds to cargo

myosin 11- dimer
- tails organized in a coiled-coil