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BIO 2600 > Chapter 17 > Flashcards

Chapter 17 Flashcards

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Biology 101 flashcards
1
Q

Three types of cytoskeleton filaments, widest to thinnest

A

Microtubules, Intermediate filaments, and Actin

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2
Q

Intermediate filaments function and properties

A

withstands mechanical stress of stretching
high tensile strength (deform but don’t break)
distribute strength among tissue cells through desmosomes
form nuclear lamina/extend through cytoplasm

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3
Q

Intermediate filament structure

A

monomers contain central rod domain and unstructured regions at both ends
rod domains (a-helical) join to form coiled coil dimer
staggered antiparallel tetramer of two dimers
lateral association of 8 tetramers add together to form filament
NO STRUCTURAL POLARITY
unstructured regions vary and are exposed on the outside of filament

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4
Q

cytoplasmic intermediate filaments

A

keratin (epithelial cells) - most diverse
vimentin/vimentin-related (connective tissue, muscle, glial cells)
neurofilaments (nerve cells)

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5
Q

nuclear intermediate filament

A

nuclear lamins form nuclear lamina
NOT rope-like, mesh-like

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6
Q

mutations in keratin cause what

A

skin more prone to blistering, even with gentle impact- epidermolysis simplex

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7
Q

mutations in neurofilaments cause . . .

A

ALS; Amyotrophic lateral sclerosis

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8
Q

nuclear lamina

A

meshwork of IF beneath nuclear envelope
attachment sites for chromatin
comprised of lamin proteins
help position chromosomes

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9
Q

defects in nuclear lamina cause . . .

A

progeria; rare class of premature aging disorders due to nuclear instability, leading to defects in cell division and chromosomal positioning

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10
Q

how is the nuclear lamina regulated by phosphorylation for disassembly/reassembly for cell division

A

phosphorylation by kinases weakens interactions between tetramers
dephosphorylation by phosphatases strengthens and rebuilds

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11
Q

function of nuclear lamina in connecting nucleus to cytosol and examples

A

Accessory proteins in membrane crosslink IFs to other cytoskeletal components outside the nucleus
Plectins: cytosolic bundling of IFs, connects nuclear lamina to cytosolic components
SUN and KASH: transmembrane proteins, link nucleus to cytoplasm, nuclear positioning

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12
Q

microtubules monomers

A

tubulin dimers made of alpha and beta tubulin, held together by noncovalent bonds

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13
Q

function of centrosomes

A

microtubule organizing center (MTOC) from which microtubules grow and extend out to the rest of the cell

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14
Q

main functions of microtubules

A

guide transport of vesicles, organelles, and other cell components
form mitotic spindle during cell division
found in flagella and cilia

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15
Q

which tubulin subunit is plus end/minus end

A

alpha = minus end
beta = plus end

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16
Q

tubulin monomer assembly into filaments

A

linear protofilament of dimers
13 protofilaments form microtubule all oriented in same direction (structural polarity)

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17
Q

tubulins easily add to which end of the MT filament

A

plus end

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18
Q

centrosomes structure

A

two centrioles surrounded by protein matrix

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19
Q

gamma tubulin location and function

A

rings found in centrosomes that serve as nucleation sites foe MT filaments
dimers add to gamma ring

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20
Q

which end of the MT filament is embedded in the centrosome and which ends extends into cytoplasm

A

minus ends embedded in centrosome
growth occurs at plus ends in cytoplasm

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21
Q

dynamic instability

A

each MT filament is constantly growing and shrinking independent of neighboring filaments due to GTP hydrolysis

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22
Q

requirements for a formed microtubule to persist instead of rapid disassembly

A

both ends protected from depolymerization
MINUS ends protected by organizing centers
PLUS ends stabilized by capping proteins
SELECTIVE STABILIZATION

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23
Q

when are MTs more stable/less stabel

A

more stable in polarized and differentiated cells (nerve cells)
less stable in dividing cells

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24
Q

which way to MT filaments all point to create structural polarity in neurons

A

plus end toward axon terminal

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25
Q

function of motor proteins

A

intracellular transport; bind to MTs and cargo (directly or via adaptors)

26
Q

which direction to kinesins and dyneins move

A

kinesins move toward + end
dyneins move toward - end

27
Q

How does ATP hydrolysis cause movement of motor proteins

A

ATP hydrolysis Pi release loosens attachment of rear motor head to MTs
ATP binding to front motor head changes conformation flipping rear motor head to the front

28
Q

kinesins and dyneins structure

A

dimers of globular ATP binding head and tail

29
Q

kinesins attach to which organelle

A

ER membrane (via receptor proteins)
pull it outward to maintain ER network

30
Q

dyneins attach to which organelle

A

attach to Golgi and pull it inward
keeps it close to nucleus

31
Q

cilia and flagella MT structure

A

9 + 2 array
9 dimers around outside of tube, 2 in center

32
Q

mechanism of cilia and flagella movement

A

created by bending microtubule
ciliary dynein attached to adjacent microtubules to generate sliding force (ATP)
flexible protein links convert sliding motion to bending motion

33
Q

when does the growing MT begin to shrink

A

when GTP hydrolysis catches up to growing end (GTP cap lost) and GDP bound tubulin has lesser affinity for binding so filament rapidly disassembles

34
Q

what type of tubulin is added to growing end of MT

A

GTP bound tubulin added to growing MT, high affinity for one another

35
Q

actin filaments main function

A

modify cell shape during division
form contractile ring
cell movements of protists/neutrophils

36
Q

Actin filament location

A

found in bundles more than individual filaments; throughout cytoplasm
concentrated in cell cortex

37
Q

Actin structure and characteristics

A

long thin and flexible
2 twisting strands of actin globular monomer
contains plus and minus end (POLARITY)

38
Q

actin treadmilling

A

ATP-acting added to plus end and ADP-actin falls off minus end at same rate

39
Q

actin-monomer binding proteins example

A

formin, ARP complex, monomer sequestering protein

40
Q

actin filament binding proteins examples

A

severing protein, cross-linking (cortex), capping, side-binding (tropomyosin), motor protein, bundling (in filopodia)

41
Q

the leading edge of cell movement process

A

driven by actin polymerization
lamellipodia and filopodia stretch forward with plus ends pointing towards PM

42
Q

lamellipodia

A

flat sheet-like dense meshwork of actin

43
Q

filopodia

A

thin stiff loose bundle of actin

44
Q

where is the nucleation complex for actin filaments

A

growing edge (plus end) of filaments

45
Q

function of ARPs in formation of lamellipodia

A

branched actin filaments grow from ARPs on existing filaments; plus ends protected by capping filaments

46
Q

function of formin

A

promotes formation of unbranched filaments - filopodia

47
Q

3 steps of cell movement forward

A

protrusion
attachment
traction

48
Q

protrusion

A

actin polymerization at leading edge pushes PM forward and forms new actin cortex

49
Q

attachment

A

new anchorage points made between actin and surface on which cell is crawling
-integrins anchoring proteins

50
Q

traction

A

contraction at rear of cell draws body forward, old anchorage points at back released
-myosin motor proteins

51
Q

Actin binding proteins respond to extracelullar signals and control actin filaments through . . .

A

surface receptors that activate signaling pathways which converge on Rho GTPases (molecular switches by GTP hydrolyzation)

52
Q

myosin I

A

actin dependent motor protein
found in all cell types
one head domain (actin) and one tail (varies)
ATP driven
travels minus to plus end

53
Q

myosin II

A

actin dependent motor protein
mainly in muscle cells
2 heads and coiled coil tail
tails associate to form filaments
bipolar-heads extend in dif directions
travels minus to plus

54
Q

which part of myosin II interacts with actin to slide actin filaments over each other

A

heads; this causes muscle contraction and contractile ring during cell division

55
Q

skeletal muscles makeup

A

striated appearance
made of numerous, very long multinucleated cells (aka muscle fibers) that contain numerous myofibrils

56
Q

myofibril structure

A

chain of sarcomeres

57
Q

sarcomere structure

A

two Z discs attached to actin filments (thin) at plus end
actin filaments attached to central specialized myosin II filaments (thick)

58
Q

why do muscles contract

A

synchronized sarcomere shortening
actin and myosin slide past each other because of myosin heads walking toward plus ends

59
Q

why do muscle cells relax

A

myosin heads release actin filaments and sarcomeres lengthen again

60
Q

how do muscle cells respond to signals to contract

A

action potential spreads to myofibrils via T tubules (extensions of the PM into the cell)
T tubules open voltage-gated Ca+2 channels, which also mechanically opens sarcoplasmic reticulum Ca+2 channels
increased Ca+2 within the cell binds to troponin and induces conformational change
troponin change causes tropomyosin to not block myosin binding sites on actin anymore and initiate contraction

61
Q

what happens to the Ca+2 after elctrical signal passes to relax cells

A

Ca+2 pumped back into sarcoplasmic reticulum

62
Q

process of myosin moving along actin

A
  1. myosin w/no ATP or ADP bound tightly to actin
  2. ATP binds and myosin detaches from actin
  3. ATP hydrolysis causes a conformational change in myosin so displaced along actin filament (ADP and Pi attached to myosin still
  4. ADP-bound myosin weakly binds to new actin site, causing release of Pi and return to original conformation
  5. myosin loses ADP and tightly binds to new region of actin

BIO 2600 (15 decks)

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