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molecular motors Flashcards

1
Q

larger objects almost do not

A

diffuse in the cell–> due to the cytoplasm being crowded

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2
Q

molecular motors ar

A

mechano-enzymes

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3
Q

mechano enzymes

A

protein complies that utilise ATP to walk along the cytoskeleton e.g. mechanical motors

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4
Q

what do molecular motors do

A

walk along the cytoskeleton (F-actin and microtubules), carrying cargo such as organelles

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5
Q

which parts of the cytoskeleton do molecular motors work on

A

F-actin and microtubules

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6
Q

examples of molecular motors

A

kinesin, dynen, myosin

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7
Q

without ATP

A

motors cannot attach tightly

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8
Q

once the motor is attached–> tight binding

A

hydrolysis and a ‘power stroke’ occur and this causes the movement of the motor and also the release of ADP and pi

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9
Q

initially motors attach

A

weakly, then ATP binds and tight binding occurs

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10
Q

myosin and kinesis go towards..

A

the PLUS end of microtubules or F-actin

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11
Q

dynein walks to

A

the MINUS end

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12
Q

kinesin

A

dances on the microtubules using several protofilaments

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13
Q

dynein

A

stays on the same protofilament and walks in a straight line

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14
Q

motor recycling

A

kinesin and dyneon ind tot he same cargo- they can be active in transport or a passive passenger e.g. kinesis can be carried along with a cargo by myosin V molecular moto

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15
Q

myosin II

A

muscle myosin

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16
Q

Myosin V

A

membrane trafficing

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17
Q

how can one prove that motors are mechano enzymes

A

using microscopes and GFP–> fluorescent microtubules ‘slide’ over a layer of glass attached kinesis motors –> motors move latex beads n ceil-free assays

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18
Q

myosin motors are used in

A

muscle function

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19
Q

40% of your body is

A

muscle

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20
Q

20% of the muscle is

A

protein

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21
Q

12-15%

A

actin

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22
Q

skeletal muscle mainly consists of

A

myosin and F-actin- striated

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23
Q

the sarcomere is the reason it looks

A

striated

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24
Q

muscle organisation

A

sarcomere–> muscle fibril –> muscle cell–> muscle

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25
why bright and dark parts
think and thick filaments only cross over at some points
26
thick filaments consists of
myosin 2--> with motor protein heads and tail --> motor head will stick out
27
z line
the two parts that come closer tofether
28
dark band
decreases in size during contraction as the filaments cross each other
29
thin filaments consists of
f-actin and associated proteins
30
in a relaxed muscle there will be no interaction between
myosin heads and actin filament
31
tropomyosin
wraps around thin filaments and holds troponin complexes in place
32
how is contraction controlled
1) stimulus for neutron spreads over the plasma membrane 2) depolarisation of men. Calcium released from sarcoplasmic reticulum into cytoplasm 3) bind of calcium to troponin releases the block of the myosin binding site on actin 4) myosin now binds actin and walks towards the Z-disk--> contraction 5) calcium is removed by calcium pumps and myosin releases the actin filament and slides back --> relaxation
33
cardiac myocytes
form another type of straight muscle
34
cardiac muscle
is less order but the structural and mechanistic principles are the same --> spontaneous contraction
35
flagella and most cilia are
motile structures
36
cilia
-numerus per cell - function in fluid and particle movement -back and forth motion 12-230 beats per second
37
flagellum
- few or one per cell - cell locomotion - propella like motion - 10-40 beats per second
38
can be distinguished due to
different movement - cilia--> back and forth - Flagellum--> propel like motion
39
what si the core of cilium/flagellum called
axoneme
40
axoneme
core of flagellum and cilia made from microtubiles
41
ultrastructure of the standard cilium
9 microtubules, with outer and inner arm dynein - structure is hollow - outer: 3 motor heads - inner- 2 motor heads
42
cytoplasmic dynein is different to
dynein found in cilium
43
outer of cilium
3 motor heads
44
inner of cilium
2 motor heads
45
centrioles and flagella
form the basal bodies of the flagella
46
basal bodies
is a protein structure found at the base of a eukaryotic undulipodium (cilium or flagellum).
47
centrioles structure
made up of a mother centriole and daughter centriole joined by a flexible linker
48
axonemal dynein is ..
variable in its molecular structure: having 3 heads (alpha, beta, gamma) on outer and 2 heads on inner (alpha and beta)
49
flagella dynein
connects adjacent microtubules--> sliding movement similar to in the sarcomere
50
flagella dynein and movement
B-tubulus slides against A-tubulies and this leads to bending activity against the protein bridges between the tubules
51
most cells form a
non-motile primary cilium
52
non-motile primary cilium function
Detects signals that govern cell proliferation. senses flow and bending --> triggering various pathways --> essential for developmental processes
53
motile cilia vs non-motel cilia
motile cilia: generating flow and cleaning surfaces- has dynein, nexins, spokes and central microtubule pair non-motile: sensing environmental cues: chemo, mechano, thermosensation e.g. a stimulus results in mem. depolarisation
54
examples of non-motile cila
rods and cones in the eye retina - rhodopsin discs are found in the cilium. - photoreceptors in the human eye are specialised cilium
55
IFT
intraflagellar transport
56
intraflagellar transport
supports the formation and function of cilium - rafts travel along the axoneme - kinesin and dynein drive the bidirectional transport
57
kinesin II in cilia
anterograde
58
dynein in cilia
retrograde
59
what supports cell migration
actin treadmilling
60
examples of cell migration
amoeba and human phagocytes
61
f-actin in a fibroblast
- f-actin concentrates at the leading edge of the cell--> f actin grows via tread milling--> appears as waves - overtime cell will grow - leading edge is at the from of the cell directing the end part of the cell which is called the tail
62
role of cell motility (3)
1) protects against pathogens--> neutrophil chases bacterium 2) cell motility helps with healing wounds--> when skin tears cells actively move in to close the wound 3) organ development--> neurones that extend neurites
63
treadmilling
as one unit leaves another joins
64
actin organisation in a fibroblast
stress fibre nearer the centre of the cell has contractile function. Cell cortex- gel like network. Filopodium- extension from the cell which contain tight parallel bundles
65
these stress fibres in fibroblasts are
contractile like muscle--> form fibres of f actin and myosin II (muscle myosin)
66
steps during cell migration
1) extension 2) adhesion 3) translocation 4) de-adhesion
67
name a cytoskeleton dependent process
intracellular membrane trafficking
68
motors are responsible for
intracellular motility--> not just vesicles, but entire organelle e.g. they transport organelles along microtubules
69
cool motor example
motors change the colour of the fish skin. the dispersal and conc depends on kinesis, dynein that move along the microtubules - change in black part of fish is due to a change in mem. trafficking e.g. organelles containing melanin are moved to the centre and then the vesicles get dispersed outwards and make the whole cell look darker
70
what shape the ER and make them mobile
motors - the ER will also form without pro - ER grows paallel on the microtubules- another way to be distributed
71
the ER will also form without proteins so..
not just due to molecular motors
72
axonal transport keeps
the cell alive and connects the synapses in the cell body--> in neurons
73
why is axonal transport important in neurones
have to cope with long distance - the synapse must communicate with the cell body in order to keep the neurone alive - the distance to overcome may be meters! (Giraffes)
74
axonal transport
is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts (i.e. organelles) to and from a neuron's cell body, through the cytoplasm of its axon (the axoplasm).
75
dynein and kinesin in a neurone
In axons there is a MINUS end (cell body) and a PLUS end (synapse) - ->synapse to cell body is done by dynein proteins (retrograde signaling) - ->cell body to synapse is done by kinesin (antergrade)
76
in neutrons growing and shrinking in the axon is suppressed
1) microtubule-binding proteins stabilise dendrite
77
If microtubules depolarise (shrinking) the transport stops- leading to
the cells death

Molecular cell (21 decks)

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