Lecture 2 Flashcards
1
Q
Cytoskeleton organization
A
- Microtubules transport vesicles and proteins to different ends of the cell
- Polarized actin define cell shape and behavior
- Intermediate filaments contribute to cell polarity
- Interphase: Microtubules radiate from cell center, Actin enriched at cell cortex
- Mitosis: Microtubules form mitotic spindle, Actin at cell cortex disassembles
- Cytokinesis: Microtubules keep cell components seperate, Actin form contractile ring
2
Q
Microtubules
A
- Alpha(-) and Beta(+) tubulin form dimers, hydrolyze GTP
- Assemble head to tail to make polarized protofilaments
- 13 protofilaments form hollow microtubule
- Rapid loss and gain of GTP cap cause dynamic instability. Alpha tubulin GTP bound
- y-tubulin interact with alpha-tubulin at (-) end. Nucleates/stabilizes (-) end and protect from depolymerization
- y-tubulin found near centrioles
- kinesin go toward (+) end, dynein go toward (-) end. Use ATP hydrolysis for energy
3
Q
Actin Filament
A
- Actin monomers asymmetric, hydrolyze ATP. actin monomers assemble into polarized actin filaments(two strand twist together)
- ARP2/3 complex nucleate (-) end of actin filaments. Undergo treadmilling
- Growing actin network pushes leading end forward, actin/myosin contract to bring lagging edge forward
- Integrin heterodimer directly bind extracellular matrix proteins, indirectly interact with actin filaments
- Myosin use ATP hydrolysis for energy -> walk toward (+) end
- Rac-GTP push cell forward, Rho-GTP push back of the cell
4
Q
Cell polarity
A
- C.elegans: sperm entry define posterior
- Trigger cytoskeleton polarization at fertilized egg
- Actin organized by Rho-GTP activity
- Microtubule organized by centrosomes where sperm enter