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BB10005- Cell Biology > Cytoskeleton lec 1 (lecture 10) > Flashcards

Cytoskeleton lec 1 (lecture 10) Flashcards

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1
Q

Describe the cytoskeleton on whether you think it is dynamic?

A

SOME!!: highly dynamic

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2
Q

10 functions of the cytoskeleton?

A
  • mitosis
  • cytokinesis
  • traffic (diffusion of protein is not random
    )- Sperm to swim (flagella: eus and pro different (structure))
  • White blood cells to crawl (
  • Muscle contraction
  • Formation of axons/dendrites
  • Cell shape
  • Growth of plant
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3
Q

Three types of cytoskeleton (and their diameters)

A
  • Intermediate filaments (10nm)
  • Microtubules (20nm diameter (large))
  • Actin filaments (7nm) – smaller
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4
Q

Stability of intermediate filaments

A

STABLE, rarely undergo rearrangement

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5
Q

Function of the intermediate filaments, abundance where?

A

add strength to cells, therefore abundant in cells which require mechanical strength eg skin cells

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6
Q

Where else do we find intermediate filaments other than the cytoplasm

A

nucleus, neurofilaments

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7
Q

How do intermediate filaments arrange themselves (generally)

A

monomers, which self associate to form multimeric structures

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8
Q

Keratin?

A

type of intermediate filament found in epithelial cells

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9
Q

Vimentin ?

A

type of intermediate filament found in connective and nerve tissue

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10
Q

Intermediate have what type of termini ? And between?

A

Globular N and C termini with a long alpha helical stretch of non polar amino acids

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11
Q

Average length of an individual intermediate filament?

A

48nm

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12
Q

coiled-coil Dimers of intermediate filaments are formed when?

A

Two monomers of intermediate filament protein associate to form a dimer by coiling their alpha helices around each other

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13
Q

Staggered tetramers are formed by?

A

Two dimers lining up

antiparallel n >c C>N

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14
Q

How to tetramers interact ?

A

N-termini of the monomers (in one dimer) interact with the C-termini of adjacent monomers (in another dimer).

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15
Q

Rope like structures of intermediate filaments are formed when?

A

Eight tetramers are twisted into a rope of diameter approx 10 nm

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16
Q

‘Cell junctions’ cause interaction between cells by?

A

Indirectly connected to filaments of other cells through cell-cell junctions called desmosomes to neighbouring cells

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17
Q

Cadherins function ?

A

span the two
membranes and bind the 2
cells together

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18
Q

Cadherins interact with?

A

Plaque proteins on the cytosolic side of membranes

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19
Q

Plaque proteins interact with?

A

The plaque proteins interact with keratin filaments

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20
Q

Order of interactions between cells and different molecules from one cell to another?

A

Keratin to plaque to cadherin (in and inside the membrane of both cells) to plaque to keratin

HENCE INDIRECTLY

21
Q

Example of an Intermediate filament disorder?

what type of disorder

effects?

A

Epidermolysis bullosa simplex

rare, recessive

Keratin cannot form normal filaments in the skin, prone to mechanical injury

22
Q

Nuclear lamina, purpose ?

A

a network of intermediate filaments beneath the nuclear membrane

Give the nucleus its shape

23
Q

Laminins are what type of proteins?

A

Extracellular matrix proteins, NOT CYTOSKELETAL proteins

24
Q

When cells are treated with salt or ionic detergent?- iNTERMEDIATE FILAMENTS

A

They remain largely in tact

25
Q

Actin abundance

A

very

26
Q

Where is actin found

A

all eu cells

27
Q

Actin Filaments made up of?

A

small globular proteins, nearly end to end

28
Q

Stability of actin

A
  • Usually unstable
29
Q

Dynamic nature of actin filaments

A

DYNAMIC

30
Q

Free actin?

A

G- actin

31
Q

When G-actin associates

A

f- actin

32
Q

Experiment with G and F actin?

A

Take actin monomer and have them in vitro,
put g atin in a test tube,
add ATP, salt, mg, k, g
actin will spontaneously begin to form filaments (F-Actin) (as long as conc of actin is high enough)

33
Q

Critical concentration?

A

Concentration of G-actin needed to polymerise spontaneously

34
Q

Why in vivo does actin reach a maximum of polymerisation?

A 
Polymerisation is balanceed with depolymerisation 
still changing (dynamic) but chain length is not increasing
35
Q

Polarity of acton filaments?

A

POLARITY NOT DUE TO ELECTRICAL CHARGE

  • Globular
  • 2 lobes
  • Minus end (ATP binding clef exposed)
  • Plus end (dome of actin exposed)
36
Q

proteins which bind to actin to modify its properties (6)

A 
Monomer binding proteins
Nucleating proteins
Cross linking proteins
Capping proteins
Bundling proteins
Motor proteins
37
Q

Motor proteins function ?

A

Associates with actin, moves along filaments (have directionality)

38
Q

Nucleating proteins function?

A

actin filaments at membranes

determines where assemble happens

39
Q

Describe the function of the drug Cytoclasin D?

A

binds to the +ve end of F-ACTIN, prevenst further addition at + end

40
Q

Phalloidin drug function?

A

mushroom, binds to F-actin and prevents actin filaments from depolymerising, stabilises, stops cells from crawling

41
Q

Functions of actin

A

Mechanical strength and cell shape
Cell crawling
Muscle contraction
Organelle movement

42
Q

Where are actin filaments concentrated?

A

are usually concentrated in a layer just below the plasma membrane (cortex)

43
Q

Actin binding proteins function?

A

Actin binding proteins link actin filaments into a meshwork

44
Q

Actin filaments provide what characteristic to cells?

A

Provide mechanical strength and cell shape

45
Q

Filipodia

A

are finger/needle like projections of the plasma membrane

46
Q

Lammelipodia

A

are sheet like projections of the plasma membrane

47
Q

Intergrins function within cell crawling?

A

Integrins (filopodia and lammelipodia) adhere to extracellular matrix, cells use internal contractions to pull itself forward

48
Q

Cell crawling is controlled by

A

rho and rac gtpases

BB10005- Cell Biology (6 decks)

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