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BIOL 2202 CMB Final > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

what is the cytoskeleton

A

=intricate network of protein filaments that extends throughout the cytoplasm

 ~provides cellular support to the cytoplasm and allows organization of internal cell parts
 ~functions in movement of cell and movement within the cell (transport)
 ~important in animal cell since there's no cell wall
 ~mainly a feature of eukaryotic cells
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2
Q

3 main types of protein filaments that make up the cytoskeleton

A
  • actin/microfilaments (MF)
  • intermediate filaments (IF)
  • microtubules (MT)
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3
Q

size of protein filaments largest to smallest

A

microtubules
intermediate filaments
actin/microfilaments

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4
Q

what are the subunits of each cytoskeleton protein filament

A

MF = globular actin subunits
IF = family of fibrous IF proteins
MT = globular tubulin subunits

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5
Q

describe intermediate filaments (5) and their purpose

A

=strong, ropelike fibers made up of intermediate filament proteins
=toughest and most durable
~10 nm
~thoughout the cell
~very flexible / deform under stress but do not rupture

purpose:
to give cells tensile strength which enables cells to withstand mechanical stress (withstand stretch)

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6
Q

describe intermediate filament structure

A

-2 monomer alpha helices wrap to form a coiled-coil dimer
-2 coiled-coil dimers form a tetramer with NO POLARITY
-lateral association of 8 tetramers
*groups of these 8 tetramers join along their lengths to grow a filament

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7
Q

are all IF filaments the same in structure

A

all IF proteins will have similar diameter and internal structure but the terminal domains can vary in each

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8
Q

what are the main types of intermediate filaments

A

CYTOPLASMIC
-keratin filaments MAIN WE LOOK AT
-vimentin filaments
-neurofilaments

NUCLEAR
-nuclear lamins

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9
Q

describe the types of cytoplasmic IFs

A

-keratin filaments MAIN WE LOOK AT
~in epithelial cells
-vimentin filaments
~in connective tissue cells, muscle cells
-neurofilaments
~in nerve cells

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10
Q

describe nuclear IFs

A

-nuclear lamins
~in all animal cells

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11
Q

describe IF keratin

A

-help distribute stress to neighboring cells!
-anchored to the plasma membrane by desmosomes
-in epithelial tissue

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12
Q

epithelial cells undergo a lot of _____ and _____ ______ so cells are indirectly connected to other cells thru ______

A

stretching and mechanical stress

cells thru desmosomes

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13
Q

describe IF nuclear lamina

A

-structure and support to nucleus
-in between nuclear envelope and nucleus
-important in recruiting DNA mechanisms

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14
Q

what are plectins

A

green accessory pigments that crosslink intermediate filaments into bundles as well as IFs to MTs, MFs and desmosomes

-stabilizes the IF

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15
Q

what are desmosomes

A

hold epithelial cells together in sheets and allow keratin filaments of all adjoining cells to be indirectly connected = lots of tensile strength

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16
Q

what was the first case study we did in class and what model could be used to study it

A

EB - epidermolysis bullosa
-keratin gene mutations that affect cell junctions and their attachments in the skin

-knockout mice

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17
Q

describe microtubules (5) and its key role

A

=hollow cylinder made up of globular alpha and beta tubulin proteins
~25nm
~dynamic
~very rigid, rupture when stretched
~one end attached to MTOC

key role in cell organization / provide tracks within the cell

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18
Q

describe MT structure (4)

A

-MT monomers are tubulin heterodimers bound by noncovalent bonds
~alpha-tubulin = (-) end
~beta-tubulin = (+) end
-has polarity for cells to conduct directional transport (not charged!)
-rings of 13
-includes GDP and GTP

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19
Q

which end do dimers in MT grow from

A

dimers grow/added to (+) end / beta-tubulin

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20
Q

where do microtubules arise from in the cell and the 3 types

A

-microtubule organizing centers (MTOC)

1.centrosomes
2.basal body
3.mitotic spindle

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21
Q

what is the major MTOC in animal cells

A

centrosomes

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22
Q

microtubules grow out from an ____ _____

A

organizing center

23
Q

describe centrosomes (3)

A

in animal cells
-close to nucleus
-pair of perpendicular centrioles

24
Q

which end of MT is anchored to the centrosome and by what

A

(-) end is anchored to centrosome by nucleation sites which are made up of gamma tubulin

25
Q

how are centrioles arranged

A

9+0 arrangement

26
Q

the MTOC for cilia and flagella is called ___

A

basal body

27
Q

what is dynamic instability in MTs

A

=constant shift between polymerization and depolymerization aka MTs are constantly growing and shrinking

28
Q

how are microtubules stabilized

A

capping proteins on cortex

29
Q

dynamic instability is driven by ___ _____ and what happens if it happens too early

A

GTP hydrolysis

too early = lose GTP “glue” / starts peeling and and so shrinks

30
Q

in dynamic instability describe GTP vs GDP

A

GTP - like glue / GTP cap added to grow at (+) end

GDP - less stable / shrink at (+) end

31
Q

what are MAPS with example

A

microtubule associated proteins

accessory proteins like motor proteins, plectin, EB1

32
Q

describe motor proteins in MTs and the two types

A

-used to transport / movement
-have ATPase activity to power movement

  1. kinesins - move to + end of MT
  2. dyneins - move to - end of MT
33
Q

what do motor proteins bind to (2) and which do they not

A

microtubules and microfilaments

NOT IFs!!!

34
Q

in a motor protein describe the head vs tail

A

heads = attach to microtubule and do the end over end walking via ATPase

tails = carry cargo

35
Q

describe cilia and flagella (6)

A

=motile hair-like projections from plasma membrane
-both contain bundles of microtubules and dynein
-flagella are longer
-grow from cytoplasmic basal body
-MTs are stable not dynamic
-cilia move fluid across cell (hairs) while flagella move entire cell (tails)

36
Q

what MT arrangement do cilia and flagella have

A

9+2 arrangement

37
Q

what does dynein allow for in cilia and flagella

A

dynein proteins allow for MT movement ex. MT sliding and bending

38
Q

describe microfilaments (actin) (5)

A

=thin, flexible, twisted chains of identical actin monomers
-monomers are globular actin
-has polarity
-7nm in diameter
-highly concentrated in the cortex (just beneath plasma membrane)

39
Q

what are microfilaments important in (4)

A

-microvilli
-bundles in cytoplasm
-filopodia/lamellipodia
-contractile ring

40
Q

describe microfilaments polymerization

A

-polymerization mainly at (+) end ~ Actin-ATP
-depolymerization mainly at (-) end ~ Actin-ADP

41
Q

compare polymerization/depolymerization mechanisms in microfilaments vs microtubules

size / end of growth or shrinking/ energy use/ subunits

A

Mechanisms: MT-dynamic instability
MF-treadmilling

-microtubules are larger
-MT growth/shrinking from only 1 end (+) where MF grow from (+) and shrink from (-)
-MT use GTP/GDP where MF use ATP/ADP
-MT subunits = alpha & beta heterodimers where MF subunits = globular actin

42
Q

what is thymosin

A

monomer sequestering protein / prevents polymerization (growing of actin)

43
Q

what are ARP2/3 and Formins

A

nucleating protein / promote polymerization (growing of actin)

ARP2/3 = branching
Formins = linear growth

44
Q

what is profilin

A

monomer sequestering protein / mostly prevents polymerization

45
Q

what is cofilin

A

severing protein / accelerates de-polymerization

46
Q

what is spectrin

A

cross linking protein in cell cortex

47
Q

what is chemotaxis

A

movement of cells in the direction of specific chemical signals

48
Q

describe filipodia

A

thin, stiff protrusions at leading edge etc, contain loose bundle of 10-20 actin filaments

49
Q

describe lamellipodia

A

dense meshwork of actin filaments in thin, sheet-like extensions at leading edge

50
Q

which end of actin will be close to the leading edge of plasma membrane in cell crawling

A

(+) ends

51
Q

describe cell crawling (5 steps)

A
  1. cell pushes out protrusions of cell membrane at leading edge
  2. this forms new regions of actin
  3. protrusions adhere to the crawling surface thru new points of anchorage (Integrins=allow for attachment)
  4. contraction at the rear of the cell (via myosin motor proteins) draws body of the cell forward in the direction of new attachment points/ old anchorage points are released
  5. cell pushes further protrusions and cycle repeats
52
Q

what pushes the leading edge of the lamellipodium and what assists

A

polymerizing actin filaments and ARP2/3 assists by branching

53
Q

what are the actin motor proteins

A

myosin = bind and hydrolyze ATP, providing energy for movement

54
Q

2 types of myosin and describe

A

-myosin-I
~utilize ATP hydrolysis
~move towards (+) end
~can bind to specific cargo (vesicles) or anchor on plasma membrane to reshape cell

-myosin-II
~two myosin wrapped together

BIOL 2202 CMB Final (4 decks)

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