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Molecular and cell biology > Cell polarity > Flashcards

Cell polarity Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Cell polarity

A

the organisation of proteins inside and at the surface if cells
regions of the cell have distinct protein compositions so it can have different capabilities, morphologies and functions

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2
Q

How is cell polarity generated?

A

cell surface landmarks adapting common pathways for cytoskeleton assembly
protein transport/membrane trafficking

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3
Q

What internal signals cause yeast to undergo significant morphological changes?

A

growth and division signals

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4
Q

What external signals cause yeast to undergo significant morphological changes?

A

pheromones for mating
nutritional signals like those for cell elongation

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5
Q

How can the budding events of yeast be followed?

A

staining cells with fluorescent dye called calcofluor which binds to component of yeast cell wall called chitin
allows sites of previous cell seperations to be seen as bright rings on cell walls

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6
Q

What controls where the position of new buds will be?

A

whether the cell is haploid or diploid

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7
Q

Haploid cell budding pattern

A

axial pattern
mother and daughter cells are constrained to form buds immediately adjacent to previous site of cell seperation

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8
Q

Diploid cell budding pattern

A

bipolar pattern
mother and daughter cells bud at the poles of the ellipsoidal cells

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9
Q

What genes have been identified in axial patterns?

A

BUD10
BUD3
BUD4
septins

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10
Q

What affect does mutations in axial genes have on the patten of budding?

A

mostly bud with bipolar pattern

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11
Q

What genes have been identified in bipolar patterns?

A

BUD8
BUD9
RAX2
components of actin cytoskeleton

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12
Q

What genes are required for both bipolar and axial patterns?

A

BUD1
BUD2
BUD5

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13
Q

What happens when BUD1,2 and 5 are mutated?

A

random budding pattern in haploid and diploid cells
all function together to signal to polarity establishment machinery the position of bud site landmarks

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14
Q

What proteins are important in polarity establishment?

A

Rho GTPase family
in yeast most important is Cdc42 which is highly conserved

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15
Q

Cdc42

A

small GTPase of the Rho family
regulated through cycles of activation and inactivation by binding partners Cdc24 and several GAPs

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16
Q

How does Cdc24 act on Cdc42?

A

it is its GEF- binds to active form of BUD1 at sites marked for budding
Cdc24 binds BUD1 and then activates Cdc42 to allow polarity site to be established so cell components can be trafficked to bud

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17
Q

How is cell polarity generated in order to mate?

A

haploid cells can polarise and redirect their growth axes in order to facilitate mating with partner
response is chemotropic due to pheromones being secreted by different cell types

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18
Q

MATalpha cells and MATa cells

A

MATalpha- secrete alpha-factor, which binds to MATa cells
MATa- secrete a-factor, which binds to MATalpha cells

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19
Q

How do daughter cells have different properties to mother cells?

A

myosins Myo2 and Myo4 are required for asymmetric inheritance of specific factors

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20
Q

How is backward movement of organelles in daughter cells prevented?

A

cargo adaptors are degraded

21
Q

Why can’t yeast be used to understand intercellular interactions?

A

they are unicellular so can’t study growth of tissues and multicellular organisms

22
Q

Candida albicans

A

benign member of mucosal flora but can cuase mucosal disease and become invasive
frequently seen in AIDS patients, premature babies and terminally ill patients
fungus can leave bloodstream and penetrate cells/tissues

23
Q

How can candida albicans become pathogenic?

A

switch from yeast to hyphal form is stimulated at 37 degree by serum or neutral pH
hyphae are more adherent to mammalian cells and penetrate tissue
yeast cells taken up by macrophages can become filamentous and lyse it
yeast cells carried effectively in bloodstream promoting fungal dissemination in body

24
Q

What are the two main routes to diversity?

A

polar mother cells divide to generate daughters that have inherited different components
daughters equal at birth become different by exposure to different signals/environments

25
Q

Important steps in generating cell polarity and cell fate decisions

A

establishment of axis of polarity
mitotic spindle being positioned on axis
cell fate determinants being distributed differentially among daughter cells

26
Q

Par proteins

A

form the core of a cell polarity network in many animal cells and in many developmental contexts

27
Q

Asymmetric cell division in c.elegans

A

starts with entry of sperm into oocyte, position of this will define the posterior end of oocyte
divides asymmetrically along anterior posterior axis to produce larger anterior and smaller posterior cell

28
Q

How does mutation in Par affect size and fate?

A

difference in cell size and fate between 2 daughter cells is less pronounces and can even be identical

29
Q

How is symmetry broken during fertilisation?

A

when sperm delivers microtubule organising cell which becomes posterior pole and defines axis of polarity

30
Q

How do the microtubules generated create the poles?

A

microtubules recruit Par 1/2 which antagonise anterior par proteins
they accumulate at anterior cortical domain
results in distinct localisations of par proteins

31
Q

Where do the different par proteins go?

A

1/2- posterior
3/6- anterior
5- maintains boundary

32
Q

How is the mitotic spindle organised?

A

interactions between microtubules and the cortex results in pulling forces which act on the mitotic spindle to be displaced toward the posterior end

33
Q

Neuroblast division in drosophila

A

progenitor cells in a specific region of the epithelial monolayer called the ventral neuroectoderm
assymetric cell divisions give rise to small basal daughter cells called ganglion motor cells, and larger apical daughter cells

34
Q

Hwo do ganglion motor cells and apical daughter cells divide differently?

A

GMC- only once more into a neuron and a glia cell
ADC- continue to divide asymmetrically

35
Q

When is polarity established in drosophila?

A

when cell is delaminating and still in neuroectoderm
localise to apical region
in fully delaminated nueroblasts polarity is independent of surrounding cells

36
Q

Drosophila cell fate determinants

A

transported in a basal direction to the ganglion mother cell
includes prospero and staufen

37
Q

What are the three stages of cell migration?

A

protrusion
attachment
traction

38
Q

Protrusion

A

pushing out of the plasma membrane in front of the cell

39
Q

Attachment

A

the actin cytoskeleton inside the cell is attached via interacting proteins across the plasma membrane to the substratum

40
Q

Traction

A

the bulk of the cell body is drawn forward through a process of contraction

41
Q

What are the two different types of protrusion?

A

filopedia- dense core of bundled actin filaments uses Cdc42
lamallipodia- sheet like, broad structures uses Rac

42
Q

Chemotaxis

A

the movement of cells toward or away from a signal such as a diffusible chemical
neutrophil moving to site of infection

43
Q

How do neutrophils use chemotaxis?

A

receptors on surface of neutrophils detect low levels of bacterial peptides
peptides bind to GPCRs which triggers intracellular activation of G protein
leads to activation of Rac GTPase
leads to lamellipodial protrusion in direction of peptide gradient

44
Q

When is de novo polarity set up in drosophila?

A

during embryo cellularisation

45
Q

What are the effects of EMT?

A

loss of e cadherin
assymetric activation of small Rho GTPases

46
Q

Cla4 + Ste20

A

PAK protein kinases
links polarity to cell cycle

47
Q

Sec3

A

part of the exocyst complex
ensures polarised trafficking

48
Q

Bni1

A

nucleate actin filaments
maintians polarity of cytoskeleton

Molecular and cell biology (8 decks)

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