lec 13-14 cell movement

Question 1

similarities of cilia and flagella

Answer 1

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

Question 2

differences between cilia and flagella

Answer 2

flagella are longer

different facilitation of movement - waving of flagella, beating of cilia

Question 3

3 main structural components of flagella

Answer 3

filament
hook
basal body

Question 4

flagella filament

Answer 4

rigid, helical structure
extends from cell surface
made of flagellin protein
forms a hollow core
propels bacterium when rotated by motor

Question 5

flagellum hook

Answer 5

sharp bend outside outer membrane
attached to basal body
passes movement from motor to filament

Question 6

basal body

Answer 6

made from centrioles
anchors microtubules - MTOC

usually composed of 9 doublet microtubules

Question 7

proton motive force

Answer 7

powers flagellum motor
flow of protons down gradient

rotational speed of flagella depends on intensity of it

Question 8

transition zone

Answer 8

electron dense region
‘stop-gap’
any cytoplasm above the zone is cytoplasm specific for flagella

Question 9

9+2 axoneme

Answer 9

9 sets of doublets surrounding the central pair of 2 single microtubules

dynein arms and nexin linkages

radial spoke

surrounded by plasma membrane

Question 10

structure of a doublet microtubule

Answer 10

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

Question 11

radial spoke

Answer 11

T shaped protein complex

projects inwards from each set of doublets towards central microtubules

Question 12

assembly of cilia and flagella

Answer 12

assembled from the tip not basal body

Question 13

intraflagella transport - IFT

Answer 13

bi-directional movement of particles along doublet microtubules

essential for formation and maintenance of cilia and flagella

Question 14

kinesin motors

Answer 14

kinesin II transport IFT particles towards flagellum plus end
conformational change changes affinity of head domain

Question 15

dynein motors

Answer 15

dynein 1b transports IFT particles towards flagellum minus end
2 head domains
lagging head forwards step, conformational change causes change of affinity

Question 16

mutation in centrin protein gene

Answer 16

basal bodies form incorrectly
central pair missing
too many flagella

Question 17

Uni1

Answer 17

transition zone mutant

Question 18

central pair microtubules

Answer 18

nucleated at basal plate (area rich in gamma tubulin)

open washer structure - allows microtubules to be formed

Question 19

cells lacking gamma tubulin

Answer 19

do not form central pair

outer 9 not affected

Question 20

dynein arms

Answer 20

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

Question 21

primary ciliary dyskinesia

Answer 21

no links between A and B microtubules

Question 22

movement required in single celled organisms to..

Answer 22

find food and escape predators

Question 23

3 axis of embryology

Answer 23

left/right symmetry
dorsal
anterior

Question 24

stages of cell migration

Answer 24

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

Question 25

microfilament structures in the cell

Answer 25

stress fibres
filopodia - projections that extend beyond lamellipodium
lamellipodium - primary area of actin incorporation

Question 26

critical concentration

Answer 26

when there is enough actin in a cell that it can polymerise spontaneously

Question 27

rate-limiting step in actin formation

Answer 27

nucleation

Question 28

Arp2/3 complex

Answer 28

essential for branching in lamellipodia

important for forming the base of filopodia