cytoskeleton

Question 1

what are the functions of the cytoskeleton?

Answer 1

• 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

Question 2

what is the cytoskeleton composed of?

Answer 2

protein filaments within the cytoplasm of the cell

Question 3

what are the three main protein filaments of the cytoskeleton?

Answer 3

actin(micro) filaments
microtubules
intermediate filaments

Question 4

what are microfilaments and microtubules made of?

Answer 4

globular proteins that can assemble and disassemble within the cell

Question 5

what are intermediate filaments made of?

Answer 5

fibrous protein subunits

Question 6

what is a key characteristic of the intermediate filaments?

Answer 6

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

Question 7

what are filaments responsible for?

Answer 7

cell movements
- muscle contraction
- movement of cilia

Question 8

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

Answer 8

active contraction

Question 9

what are the contractile elements of the skeletal muscle cell?

Answer 9

myofibrils

Question 10

what is the skeletal muscle cell actually called?

Answer 10

muscle fiber

Question 11

how are muscle fibers formed?

Answer 11

fusion of many cells together making it a multinucleated cell

Question 12

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

Answer 12

myofibrils

Question 13

what are myofibrils made of?

Answer 13

sarcomeres

Question 14

what are sarcomeres?

Answer 14

repeating units of cytoskeletal proteins

Question 15

what is the smallest contractile unit of the muscle cells?

Answer 15

sarcomeres

Question 16

what unit gives the muscles its striated appearance?

Answer 16

sarcomeres

Question 17

what is the A band?

Answer 17

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

Question 18

what is the H zone?

Answer 18

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

Question 19

what is the I band?

Answer 19

part of the sarcomere that contains only thin filaments

Question 20

what happens to the sarcomere as the muscle contracts?

Answer 20

the filaments slide past each other and the sarcomere gets smaller

Question 21

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

Answer 21

thin: move closer
thick: stay in same space

Question 22

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

Answer 22

shorten

Question 23

what is the sliding filament model?

Answer 23

describes how the thin filaments slide past the thick filaments

Question 23

what is the sliding filament model?

Answer 23

describes how the thin filaments slide past the thick filaments

Question 24

what is the contraction of muscle driven by?

Answer 24

ATP hydrolysis

Question 25

what is actin?

Answer 25

thin filament that also makes up the cytoskeleton

Question 26

what is myosin?

Answer 26

thick filaments and contains ATPase

Question 27

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

Answer 27

ATPase

Question 28

what is the cross-bridge cycle?

Answer 28

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

Question 29

what does the signal for muscle contraction travel through?

Answer 29

T-tubules

Question 30

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

Answer 30

sarcoplasmic reticulum

Question 31

what holds and releases the calcium within the muscle cell?

Answer 31

sarcoplasmic reticulum

Question 32

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

Answer 32

troponin tropomyosin

Question 33

troponin and tropomyosin do what in the absence of calcium?

Answer 33

inhibit the binding of myosin to actin

Question 34

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

Answer 34

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

Question 35

what is cilia?

Answer 35

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

Question 36

what is the purpose of cilia?

Answer 36

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

Question 37

what is the core of the cili called?

Answer 37

axoneme

Question 38

how are the microtubules of cilia arranged at the axoneme?

Answer 38

9+2 pattern

Question 39

describe the 9+2 pattern

Answer 39

- 9 doublets that make up a ring - 1 doublet in the middle

Question 40

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

Answer 40

almost all cilia and eukaryotic flagella

Question 41

what are the microtubules that make up the cilia themselves?

Answer 41

tubulin

Question 42

what is tubulin composed of?

Answer 42

alpha and beta-tubulin

Question 43

what is the basal body?

Answer 43

base from which microtubules can grow

Question 44

what is the pattern of microtubules within the basal body?

Answer 44

9+0

Question 45

what is the axoneme further stabilized by?

Answer 45

accessory proteins

Question 46

what motor protein is important for the movement of cilia?

Answer 46

dynein

Question 47

what is kartagener's syndrome?

Answer 47

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

Question 48

what are symptoms of kartagener's syndrome?

Answer 48

- recurrent upper respiratory tract infections - chronic sinusitis - infertility in males - situs inversus with dextrocardia

Question 49

what does situs inversus refer to?

Answer 49

inverting of normal position of organs in the body

Question 50

what are the feeding tubules of amoeba made of?

Answer 50

microtubules

Question 51

why can amoeba tentacles rapidly extend and retract?

Answer 51

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

Question 52

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

Answer 52

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

Question 53

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

Answer 53

anti-cancer drugs

Question 54

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

Answer 54

colchicine

Question 55

what does colchicine have the ability to do?

Answer 55

bind to a tubulin dimer and prevent its polymerization

Question 56

why is colchicine classified as an anti-mitotic drug?

Answer 56

it can be used to halt cell division

Question 57

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

Answer 57

they can preferentially kill the rapidly dividing cells found in cancer

Question 58

what is the mechanism of action used by taxol?

Answer 58

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

Question 59

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

Answer 59

true

Question 60

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

Answer 60

depolymerization

Question 61

what makes up microvilli?

Answer 61

actin filaments

Question 62

describe microvilli

Answer 62

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

Question 63

The cytoplasmic actin pool is bound to a protein called _____

Answer 63

profilin

Question 64

what does profilin do?

Answer 64

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

Question 65

list cell processes in which polymerization of actin is used

Answer 65

- locomotion - phagocytosis - cytokinesis

Question 66

what is an example of a drug that prevents actin polymerization

Answer 66

cytochalasins

Question 67

what are cytochalasins

Answer 67

group of metabolites that are released by different species of molds

Question 68

how do cytochalasins prevent the polymerization of actin?

Answer 68

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

Question 69

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

Answer 69

phalloidin

Question 70

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

Answer 70

depolymerization

Question 71

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

Answer 71

phalloidin

Question 72

what is the energy source of actin?

Answer 72

ATP

Question 73

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

Answer 73

lag

Question 74

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

Answer 74

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

Question 75

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

Answer 75

elongation

Question 76

what is the critical concentration/steady-state?

Answer 76

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

Question 77

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

Answer 77

they're polar

Question 78

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

Answer 78

positive

Question 79

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

Answer 79

negative

Question 80

what is the energy source of tubulin?

Answer 80

GTP

Question 81

where are intermediate filaments found?

Answer 81

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

Question 82

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

Answer 82

intermediate filaments

Question 83

how can intermediate filaments be broken down?

Answer 83

proteolytic enzymes

Question 84

true or false: the intermediate filaments are a dimer

Answer 84

false: trimer

Question 85

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

Answer 85

neurofilaments keratin filaments vimentin