lec 13-14 cell movement Flashcards
similarities of cilia and flagella
microtubule-based appendages that beat rhythmically
waves begin at base and propagated out to tip
immobilised- stuck in tissue
no ribosomes - proteins made in cell body
differences between cilia and flagella
flagella are longer
different facilitation of movement - waving of flagella, beating of cilia
3 main structural components of flagella
filament
hook
basal body
flagella filament
rigid, helical structure extends from cell surface made of flagellin protein forms a hollow core propels bacterium when rotated by motor
flagellum hook
sharp bend outside outer membrane
attached to basal body
passes movement from motor to filament
basal body
made from centrioles
anchors microtubules - MTOC
usually composed of 9 doublet microtubules
proton motive force
powers flagellum motor
flow of protons down gradient
rotational speed of flagella depends on intensity of it
transition zone
electron dense region
‘stop-gap’
any cytoplasm above the zone is cytoplasm specific for flagella
9+2 axoneme
9 sets of doublets surrounding the central pair of 2 single microtubules
dynein arms and nexin linkages
radial spoke
surrounded by plasma membrane
structure of a doublet microtubule
a- full microtubule with 13 microfilaments
attached to b to make the doublet
b- 2/3 of a microtubule (C-shaped)
one dynein arm also attached - projects outwards
nexin linkages join the doublets
radial spoke
T shaped protein complex
projects inwards from each set of doublets towards central microtubules
assembly of cilia and flagella
assembled from the tip not basal body
intraflagella transport - IFT
bi-directional movement of particles along doublet microtubules
essential for formation and maintenance of cilia and flagella
kinesin motors
kinesin II transport IFT particles towards flagellum plus end
conformational change changes affinity of head domain
dynein motors
dynein 1b transports IFT particles towards flagellum minus end
2 head domains
lagging head forwards step, conformational change causes change of affinity
mutation in centrin protein gene
basal bodies form incorrectly
central pair missing
too many flagella
Uni1
transition zone mutant
central pair microtubules
nucleated at basal plate (area rich in gamma tubulin)
open washer structure - allows microtubules to be formed
cells lacking gamma tubulin
do not form central pair
outer 9 not affected
dynein arms
bound to each doublet microtubule
multi-subunit complexes:
- head domains - hydrolysis of ATP creates dynein movement, bind to adjacent doublet by B microtubule
- tail domain - bound to A microtubule, immobilised , prevents movement too far away - creates bending force
primary ciliary dyskinesia
no links between A and B microtubules
movement required in single celled organisms to..
find food and escape predators
3 axis of embryology
left/right symmetry
dorsal
anterior
stages of cell migration
sensing - ahead
extension - rapid actin polymerisation at leading edge
attachment - new adhesion site made in front of cell
contraction - cytoplasm contracts
rear release - old adhesion site left behind
recycling - old receptors recycled
microfilament structures in the cell
stress fibres
filopodia - projections that extend beyond lamellipodium
lamellipodium - primary area of actin incorporation
critical concentration
when there is enough actin in a cell that it can polymerise spontaneously
rate-limiting step in actin formation
nucleation
Arp2/3 complex
essential for branching in lamellipodia
important for forming the base of filopodia
