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C Bio > Cytoskeleton Part I (24) > Flashcards

Cytoskeleton Part I (24) Flashcards

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Biology 101 flashcards
1
Q

what are the 3 types of cytoskeleton fibers?

A

microtubules

intermediate filaments

microfilaments

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2
Q

microtubules

A

hollow & rigid cylindrical tubes

made of tubulin

responsible for movement from the interior to the exterior & vice versa, but not to the periphery

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3
Q

which fiber is the largest of the cytoskeleton components?

A

microtubules

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4
Q

What fiber offers the greatest amount of strength & durability?

A

microtubules

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5
Q

microfilaments

A

solid, thinner structures

made of actin

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6
Q

intermediate filaments

A

tough, ropelike fibers

made of a variety of related PROs

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7
Q

Dynamic scaffold function of the cytoskeleton

A

Helps maintain cell shape

Shape is assoc with function

Resist mechanical restresses

Cytoskeleton can rearrange itself to change the shape of the cells

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8
Q

Intracellular transport of the cytoskeleton

A

moves materials & organelles within the cell
mRNA
ER –> Golgi
Neurotransmitter containing vesicles
Peroxisomes (move to mitochondria to deal with free radicals)

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9
Q

Force generation & motility of the cytoskeleton

A

move cells
Single-celled use cilia & flagella
Multicell use independent locomotion of an indiv cell
Dendrites stretch to make contact with the cell they need to make contact with & retract when necessary

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10
Q

what type of cells are capable of independent locomotion?

A

sperm

white blood cells

fibroblasts

highly motile tip of growing axon

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11
Q

internal framework function of the cytoskeleton

A

positions organelles

Arranged in a defined pattern along an axis from the apical to the basal end of the cell 

Interaction of PROs on an organelle’s surface which adheres to the cytoskeleton

ex: gut –> vesicles are located near the lumen of the gut to prepare for digestion

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12
Q

how is the intracellular organization disrupted? & what evidence is there?

A

drugs or mutations that interfere with the normal cytoskeleton structure

Normal: Golgi is packed around the nucleus
Mutation: Golgi is scattered & dispersed

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13
Q

microtubule structure

A

tubulin heterodimer composed of alpha & beta subunits

will polymerize to form protofilaments which form a cylinder

protofilaments are asymmetric, alpha at one end & beta at the other

All protofilaments in a single MT have the same polarity

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14
Q

how many protofilaments are in a cylinder?

A

13

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15
Q

what is responsible for the polarity of the MTs?

A

beta subunit

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16
Q

plus end of a MT?

A

Beta subunit exposed at the end

provides polarity

fastest end of growth (easier to add to the beta end)

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17
Q

minus end of a MT?

A

a subunit

slow growth or loss

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18
Q

gamma tubulin

A

looks like alpha & beta in size & shape

initiates growth of MTs

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19
Q

when does gamma tubulin dissociate from MTs?

A

after polymerization has occurred

once it gets to a certain length, the gamma subunits retract via ATP hydrolysis

20
Q

regulation of MT stability is dependent on what factors?

A

Rates of assembly & disassembly are dependent on the local tubulin concentration
More subunits available = quick growth
Polymerization is triggered by having the right amount of subunits (require GTP bound subunits)
Not enough subunits = depolymerization

Stability is dependent on presence of GTP
Enzymes present to replace GDP with GTP to retain stability
GTP hydrolysis reduces the affinity the tubulin has for its neighbor = disassembly

Stability is maintained by continuous addition of GTP labeled tubulin

21
Q

what controls a MT’s instability?

A

GTP hydrolysis when bound to tubulin

22
Q

What does a tubulin dimer require in order to bind to the MT?

A

bound GTP

23
Q

what is the effect of GTP hydrolysis on a tubulin dimer in a MT?

A

reduces its affinity for the tubulin neighbour

24
Q

how is stability maintained in GDP dimers?

A

GDP is replaced with GTP

25
Q

what triggers polymerization?

A

right amount of subunits (require GTP bound)

26
Q

what triggers depolymerization of MTs?

A

not enough subunits available

27
Q

what type of tubulin can attach to others?

A

GTP bound tubulin dimer

28
Q

what happens if MTs are with GDP for too long?

A

collapse

29
Q

what provides stability to MTs?

A

continuous addition of GTP labeled tubulin

30
Q

how does the cytoskeleton enable cell movement?

A

rapid assembly & disassembly

31
Q

how is MT length maintained?

A

removing tubulin at one end & adding it at the other

32
Q

How do MT drugs target cancer cells?

A

Cancer cells require faster cycling of tubulin to facilitate their rapid division

Cancer cells lack mitotic checkpoints & continue to divide even in the presence of a drug, but normal cells halt division until the drug is cleared

MTs are required for proper c’some segregation, cancer cells divide with improper MTs & produce inviable cells
1 daughter cell will be n & the other 3n

33
Q

MTOC

A

growth of MTs are constantly initiated (outwards from the MTOC)

34
Q

what are the 2 kinds of MTOCs?

A

2 kinds where basal bodies are assoc with:

Base of cilia or flagella

Centrosome – creates 2 poles where MTs extend 
Contain 2 centrioles surrounded by pericentriolar material
35
Q

pericentriolar material

A

cloud of PROs surrounding the 2 centrioles in a centrosome

contain gamma tubulin

36
Q

where is the MTOC located in plants?

A

embedded in the nuclear membrane, lack a centrosome

37
Q

why do animal cells have centrosome & animals don’t?

A

animal cells are more dynamic & plant cells are more rigid

38
Q

centrosome structure & what is the total of MTs?

A

2 centrioles perpendicular to each other surrounded by pericentriolar material

9 fibrils form an outer ring, each fibril is composed of 3 fused MTs

+

1 fibril in the middle with 3 fused MTs

total of 30 MTs

39
Q

function of centrioles?

A

unknown, aren’t actually involved in MT nucleation. Recruit the molecules that are involved in MT nucleation

can remove centrioles in animal cells & there aren’t any adverse effects

40
Q

function of Tau PRO?

A

ensures MTs remain parallel with one another

41
Q

MAPs

A

MT assoc PRO

stabilize MTs (even in the absence of GTP)

alter assembly & disassembly rates

crosslink adjacent MTs

42
Q

How is MAP activity controlled?

A

addition of phosphate on particular AA residues by PRO kinase –> removed from MT

removal of phosphate on particular AA residues by phosphatase –> remain on MT

43
Q

how are MAPs involved in Alzheimer’s?

A

Abnormally high phosphorylation of a MAP, specifically the tau PRO

Hyperphosphorylated tau PRO stick together into neurofibrillary tangles in neurons & cause MTs to disintegrate
Collapse – short MTs prevent normal intracellular transport & kill the cell leading to brain deterioration
Neurons are unable to move their vesicles with neurotransmitters to the periphery

44
Q

fruit flies with mutated tau PRO exhibit what kinds of defects? & what evidence is there?

A

neural, motor & cognitive

Climbing tests –> motor

courtship training - cognitive, females excrete a pheromone when rejecting males after their courting, males don’t learn to stop courting & continue to do so

neural deformations - neural

45
Q

MT stability is due to:

A

abundance of tubulins

attachment of GTP

MAPs

C Bio (30 decks)

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