cytoskeleton
organization of eukaryotic cells
“muscle and skeleton”
Four components of cytoskeleton
- microtubules
- actin filaments
- intermediate filaments
- accessory proteins
functions of cytoskeleton
- cell shape
- cell organization
- DYNAMIC (disassemble and reassemble)
- cell motility (motor proteins and cytoskeleton)
Mictrotubules
- largest tube shaped
what are microtubules made up of
- 2 building blocks (alpha and beta)
- tubulin dimer hold cell structure
what are microtubules involved in
- cell motility (flagella and cilia)
- chromosome movement during division
- organelle movements (provides a track for movement)
where do microtubules come from
centriole, each centriole has 9 sets of triplet microtubules
- arranged in a ring shape (3x9)
actin filaments/microfilaments
2 intertwined strands of actin
what are actin filaments involved in
- changing cell shape
- muscle contractions
- cell division (cleavage furrow)
- organelles moving within cytoplasm
intermediate filaments
fibrous proteins super coiled into thicker cables
what are intermediate filaments involved in
- maintain cell shape (ex: laminate A, B/C, keratin)
reassembly and disassembly?
folds into individuals actin sub units and cell moves
polarization of ends
actin filaments and microtubules polarize at different rates (+ and - end)
+ end is fast growing
- end is slow growing
accessory proteins
controlled assembly of cytoskeleton filaments
- includes motor proteins
- tail/head structure
motor proteins
molecular machines that move filaments as well as cytoskeletal filament
- can stop, start and slow cell growth
how do motor proteins work
“walk” along actin filaments
- each movement uses ATP
kinesines (microtubule based motor protein)
moves along microtubules
- structurally similar to myosin (head to tail)
- moves - –> + end of microtubule
carries cargo to plasma membrane
dyneins
move + –> - end of microtubule
- structurally unrelated to kinesine
- head/tail and stalk attached to cargo
- cilia and flagella
cilia and flagella
microtubule containing extensions that project from some cells
- plasma membrane sheathes
- dynein drives bending movement
- anchored in basal bodies
organization of cilia and flagella
organized in a 9’ + 2’ arrangement of microtubules
- held together by linked proteins and dynein
basal body structure
9’ + 0’
cross linking proteins
allow bending
Ex: flagella bending
