Title: Webstraw: Cell Bio Anki Deck / Section 7 - Cytoskeleton: Microtubules

the cytoskeleton is a network of protein filaments that extend through the cytoplasm  and consists of:
1. microfilaments
2. microtubules
3. intermediate filaments

Q: tubulin [...] are 110kDa (8nm) and cannot revert back to monomers
A: dimers

Q: alpha end is permanetly bound to [...] and beta end can [...] GTP
A: GTP; hydrolyze

microtubules can come in 3 arrangements
1. singlets: in cytoplasm
2. doublets: in cilia/flagella 
3. triplets: in basal bodies and centrioles

Q: singlets are made of [...] protofilaments forming a tube of [...] in diameter
A: 13; 25nm

Q: doublets are stable with [...] protofilaments tube attached to a [...] protofilament tube
A: 13; 10

Q: main microtubule function is [...]
A: transport

Q: there are 2 types of microtubules
1. [...]: majority of microtubules
2. [...]: specific to cilia and flagella
A: cytoplasmic; axonemal

Q: microtubule assembly is a [...] process and originates from [...]
A: dynamic; microtubule organizing center (MTOC)

Q: [...] end of microtubules associates with MTOC and [...] end of microtubules grow outwards
A: alpha (-); beta (+)

Q: [...] are an exception with no clear MTOC or direction of growth
A: dendrites

Q: centrosomes are the major MTOC in [...] cells and contain [...]
A: animal; centrioles

Q: centrioles are [...] microtubules surrounded by [...] matrix and NOT found in plants
A: triplet; pericentriolar

Q: singlet microtubules grow from [...] around centrioles
A: y-tubulin/augmin complex

Q: centrioles are placed at [...] angles to one another and are crucial for protein [...] in matrix
A: 90 degree; organization

Q: microtubules polyermization occurs after [...] is reached - [...] accelerates initial polymerization
A: critical concentraion; nuclear site

Q: polymeriztion occurs when [...] on the positive end is in [...] form (ready to be hydrolyzed) and when critical concentration is reached
A: GTP-B-cap; GTP

Q: drugs exist that alter microtubules
1. cholchine - causes [...]
2. taxol - [...] microtubles
A: depolymerization; stabilizes

Q: microtubules are dynamically [...] and (+) end is constantly growing and shrinking
A: unstable

Q: microtubules disassemble at [...] Celsius
A: 4 degrees

Q: microtubules associated proteins (MAPs) alter microtubule stability
1. [...] - stabilize microtubules
2. [...] - (+) end proteiins that stabilize and reduce catastrophe
A: MAP2 and Tau; +TIP

microtubule severing proteins causes depolymerization
1. kinesin-15 - uses ATP to rip off dimers from (+) end
2. stathmin - binds to tubulin dimers to promote fraying

Q: microtubule transportation is [...] and requires [...]
A: bidirectional; ATP

Q: microtubule movement can be imaged by [...] used as model system
A: squid axons

Q: radioactive [...] are injected into squid axons and are run through [...] to observe movement
A: amino acids; SDS-PAGE

Q: [...] is the microtubule's (+) end directed motor protein
A: kinesin

Q: kinesin are made of
1. heavy chains - head with [...] activity and [...] binding site, neck (linker), stalk
2. light chains - bind to [...]
A: ATPase; microtubule; cargo

Types of kinesin
1. Kinesin-1- organelle transport: 2 heavy with 2 light chains
2. Kinesin-2 - organelle transport: 2 heavy with 1 light chain
3. Kinesin-5 - microtubule sliding: 4 heavy chains
4. Kinesin-13- end disassembly: 2 head domains

Q: kinesin move using [...] and in increments of [...]
A: ATP; 16nm

Q: [...] is microtuble (-) end directed motor protein involved in [...] transport using ATP - transport toward MTOC
A: dyein; retrograde

Q: kinesin are invovled in [...] transport to move away from the [...]
A: anterograde; MTOC

Q: [...] are a string of dimers that can extend from the [...] end
A: protofilaments; beta (+)

Q: microtubules are polymers with [...] made of [...] tubulin
A: polarity; alpha and beta

Q: dyenein needs [...] complex to bind to cargo
1. [...] glued - acts as wheels in complex
2. [...] - links dynein to cargo and releases cargo when needed
A: dynactin; P150; dynamitin

Q: cilia is [...]um and many cilia function together to sweep material across tissue
A: 2-10

Q: flagella is [...]um and few function together to propel cells
A: 10-200

Q: the underlying structure of cilia and flagella is called the [...]
A: axoneme

Q: the axoneme is a [...]+[...] microtuble arrangement
A: 9; 2

axoneme consists of
1. 9 doublets - forms outside ring
2. 2 singlets - inside the ring
3. nexin - holds outside ring together
4. radial spoke heads - holds doublets in position
5. axenomal dynein - head extends towards next dimer

Q: the [...] is the MTOC for flagella
A: basal body

Q: the basal body consists of
1. 9 triplets - loses C tubule when passing through [...]
2. 1 singlet - becomes [...] singlets
A: transitional zone; 2

Q: basal bodies are found in pairs [...] to one another
A: perpendicular

Q: axoneme bending occurs by [...] sliding of microtubules against each other
A: local

Q: axoneme bending is powered by axonemal [...] as [...] stops sliding
A: dynein; nexin

intraflagellar transport occurs "up and down"
1. cytoplasmic dynein - moves material toward cell body
2. kinesin-2 - moves material away from cell body

Q: non-motile [...] cilium do not have axonemal [...] and are used for cell-cell signalling
A: primary; dyenin

Q: [...] is the phase of mitosis where chromosomes divide
A: karyokinesis

Q: the stability of microtubules change dramatically during karyokinesis
1. [...] - supresses catastrophes
2. [...] - induces catastrophes
A: XMAP215; kinesin-13

Q: centrosome is the [...] and facilitates novel microtubule dynamics
A: mitotic apparatus

Q: mitotic apparatus is responsible for capturing replicated [...], lining them up, and separating them
A: chromosomes

mitotic appartus consists of
1. poles - where microtubules grow from
2. polar microtubules - mt that go towards other pole without contacting chromosomes
3. kinetochore microtubules - mt that contacts chromosomes
4. aster (astral) microtubules - mt not going towards other pole

Q: [...] are the attachment site for microtubules on the chromosome
A: centromeres

Q: [...] on centromere mediate attachment of chromosomes to microtubules - space exists between to allow for [...]
A: kinetochores; polymerization

Q: microtubules polymerize/depolymerize at [...] to ensure chromsoomes are aligned at metaphase plate
1. [...] pulls chromosomes towards pole
2. [...] pushes chromsomes away from pole
A: kinetochore; dynein; CENP-E (+)

Q: [...] - when chromosomes are attached to both spindle poles
A: biorientation

Q: tension reassures biorientation - [...] in kinetochore holds microtubule and waits for tension
A: Ndc80

Q: there are 2 anaphase stages that occur simultaneously
1. anaphase A - moves chromosomes to [...]
2. anaphase B - moves [...] apart
A: poles; poles

Q: the driving force of
1. anaphase A is [...]
2. anaphase B is [...]
A: microtubule depolymerization; motor proteins