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cytoskeleton Flashcards

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Biology 101 flashcards
1
Q

what are the functions of the cytoskeleton?

A
  • helps the cell maintain its structure and organization
  • assist with changing the cell’s shape
  • reposition internal organelles
  • move cell from one place to another
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2
Q

what is the cytoskeleton composed of?

A

protein filaments within the cytoplasm of the cell

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3
Q

what are the three main protein filaments of the cytoskeleton?

A

actin(micro) filaments
microtubules
intermediate filaments

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4
Q

what are microfilaments and microtubules made of?

A

globular proteins that can assemble and disassemble within the cell

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5
Q

what are intermediate filaments made of?

A

fibrous protein subunits

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6
Q

what is a key characteristic of the intermediate filaments?

A

they’re a lot more stable than the other two filaments

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7
Q

what are filaments responsible for?

A

cell movements
- muscle contraction
- movement of cilia

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8
Q

what do all three muscle groups have in common by using which movement?

A

active contraction

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9
Q

what are the contractile elements of the skeletal muscle cell?

A

myofibrils

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10
Q

what is the skeletal muscle cell actually called?

A

muscle fiber

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11
Q

how are muscle fibers formed?

A

fusion of many cells together making it a multinucleated cell

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12
Q

what is the muscle fiber composed of that contracts in the presence of ATP

A

myofibrils

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13
Q

what are myofibrils made of?

A

sarcomeres

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14
Q

what are sarcomeres?

A

repeating units of cytoskeletal proteins

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15
Q

what is the smallest contractile unit of the muscle cells?

A

sarcomeres

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16
Q

what unit gives the muscles its striated appearance?

A

sarcomeres

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17
Q

what is the A band?

A

middle portion of the sarcomere that contains both thick and thin filaments

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18
Q

what is the H zone?

A

middle portion of the sarcomere that contains both the M band and only thick filaments

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19
Q

what is the I band?

A

part of the sarcomere that contains only thin filaments

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20
Q

what happens to the sarcomere as the muscle contracts?

A

the filaments slide past each other and the sarcomere gets smaller

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21
Q

what happens to the thin and thick filaments as the muscle contracts?

A

thin: move closer
thick: stay in same space

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22
Q

what happens to the I band and H zone as the muscle contracts?

A

shorten

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23
Q

what is the sliding filament model?

A

describes how the thin filaments slide past the thick filaments

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23
Q

what is the sliding filament model?

A

describes how the thin filaments slide past the thick filaments

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24
Q

what is the contraction of muscle driven by?

A

ATP hydrolysis

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25
Q

what is actin?

A

thin filament that also makes up the cytoskeleton

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26
Q

what is myosin?

A

thick filaments and contains ATPase

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27
Q

where does the hydrolysis of ATP for muscle contraction take place?

A

ATPase

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28
Q

what is the cross-bridge cycle?

A

once the ATP is hydrolyzed by myosin, it “walks” along the actin to make the muscle contract

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29
Q

what does the signal for muscle contraction travel through?

A

T-tubules

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30
Q

once muscle contraction travels through the T-tubules, where does it reach?

A

sarcoplasmic reticulum

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31
Q

what holds and releases the calcium within the muscle cell?

A

sarcoplasmic reticulum

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32
Q

The regulation of muscle contraction in response to increased intracellular calcium levels is regulated by what two proteins?

A

troponin
tropomyosin

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33
Q

troponin and tropomyosin do what in the absence of calcium?

A

inhibit the binding of myosin to actin

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34
Q

what does troponin and tropomyosin do in the presence of calcium?

A

calcium binds to troponin which moves tropomyosin out of the way to allow myosin to bind to actin and facilitate muscle contraction

35
Q

what is cilia?

A

hair-like extensions off of the cell that are made of bundles of microtubules

36
Q

what is the purpose of cilia?

A

move fluid that is present over the surface of the cell or move single-celled organisms through fluid

37
Q

what is the core of the cili called?

A

axoneme

38
Q

how are the microtubules of cilia arranged at the axoneme?

A

9+2 pattern

39
Q

describe the 9+2 pattern

A
  • 9 doublets that make up a ring
  • 1 doublet in the middle
40
Q

the 9+2 pattern of microtubules is a characteristic of what?

A

almost all cilia and eukaryotic flagella

41
Q

what are the microtubules that make up the cilia themselves?

A

tubulin

42
Q

what is tubulin composed of?

A

alpha and beta-tubulin

43
Q

what is the basal body?

A

base from which microtubules can grow

44
Q

what is the pattern of microtubules within the basal body?

A

9+0

45
Q

what is the axoneme further stabilized by?

A

accessory proteins

46
Q

what motor protein is important for the movement of cilia?

A

dynein

47
Q

what is kartagener’s syndrome?

A

autosomal recessive disorder that affects the motor protein dynein in the individuals body.

48
Q

what are symptoms of kartagener’s syndrome?

A
  • recurrent upper respiratory tract infections
  • chronic sinusitis
  • infertility in males
  • situs inversus with dextrocardia
49
Q

what does situs inversus refer to?

A

inverting of normal position of organs in the body

50
Q

what are the feeding tubules of amoeba made of?

A

microtubules

51
Q

why can amoeba tentacles rapidly extend and retract?

A

due to the rapid depolymerization and repolymerization of tubulin to form microtubules

52
Q

In order to keep a backup reserve of tubulin, 50% is kept where?

A

in a cytoplasmic pool so that it can help with rapid polymerization.

53
Q

Many drugs have been discovered that can disturb/prevent the polymerization of microtubules. what kind of drugs have they been used as?

A

anti-cancer drugs

54
Q

what compound was originally extracted from saffron by the ancient egyptians?

A

colchicine

55
Q

what does colchicine have the ability to do?

A

bind to a tubulin dimer and prevent its polymerization

56
Q

why is colchicine classified as an anti-mitotic drug?

A

it can be used to halt cell division

57
Q

why are the anti-mitotic drugs, vincristine and vinblastine, useful as anti-cancer cells?

A

they can preferentially kill the rapidly dividing cells found in cancer

58
Q

what is the mechanism of action used by taxol?

A

it increases polymerization so the cytoplasmic pool of tubulin is depleted leading to the discontinuation of polymerization

59
Q

true or false: Without the presence of tubulin, polymerization cannot take place

A

true

60
Q

taxol stabilizes the microtubule polymer and prevents ______________ from occurring, halting the process of mitosis

A

depolymerization

61
Q

what makes up microvilli?

A

actin filaments

62
Q

describe microvilli

A
  • thin, finger-like projections that stem from the surfaces of cells
  • can extend and retract according to the depolymerization and polymerization of actin
63
Q

The cytoplasmic actin pool is bound to a protein called _____

A

profilin

64
Q

what does profilin do?

A

prevents the polymerization of actin and keeps its concentration constant in the cell

65
Q

list cell processes in which polymerization of actin is used

A
  • locomotion
  • phagocytosis
  • cytokinesis
66
Q

what is an example of a drug that prevents actin polymerization

A

cytochalasins

67
Q

what are cytochalasins

A

group of metabolites that are released by different species of molds

68
Q

how do cytochalasins prevent the polymerization of actin?

A

by binding specifically to one end of the actin filament and preventing the addition of more actin molecules to that end

69
Q

what is an example of a molecule that can affect actin depolymerization released by the death-cap mushroom?

A

phalloidin

70
Q

phalloidin actually prevents the ____________ of actin by stabilizing the actin filaments

A

depolymerization

71
Q

what is commonly used in the lab as a cytoskeleton stain?

A

phalloidin

72
Q

what is the energy source of actin?

A

ATP

73
Q

Actin polymerization is characterized by a ___ phase, in which we can’t really see a distinct change in polymerization

A

lag

74
Q

why can’t we see a distinct change in the polymerization of actin in the lag phase?

A

because a certain amount of actin has to come together and polymerized in a nucleus

75
Q

more and more actin can be added at a much faster rate in the ________ phase

A

elongation

76
Q

what is the critical concentration/steady-state?

A

actin will be released from one end of the polymer at the same rate that actin is being added at the other end of the polymer

77
Q

actin and tubulin polymers have a positive end and a negative end, what does this tell us?

A

they’re polar

78
Q

fast-growing or elongating end is known as the _______ end (actin and tubulin polymers)

A

positive

79
Q

the actin and tubulin polymer end that doesn’t grow nearly as fast and is known as the depolymerizing or ______ end.

A

negative

80
Q

what is the energy source of tubulin?

A

GTP

81
Q

where are intermediate filaments found?

A

parts of the cell that are exposed to mechanical stress such as along a process of a neuron, or between adjacent epithelial cells

82
Q

what are the most stable components of the cytoskeleton and are also the least soluble?

A

intermediate filaments

83
Q

how can intermediate filaments be broken down?

A

proteolytic enzymes

84
Q

true or false: the intermediate filaments are a dimer

A

false: trimer

85
Q

intermediate filament classes:
neuron=
epithelial cells=
copolymerized with other proteins=

A

neurofilaments
keratin filaments
vimentin

cell bio (12 decks)

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