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Molecular Exam 2 > The Cytoskeleton I- Structure > Flashcards

The Cytoskeleton I- Structure Flashcards

Dr. White

1
Q

What is the significance of the cytoskeleton?

A

represents bones of the cell
important in organization fo the cell
maintains correctly shaped cells
insures cells are properly structured internally

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2
Q

What are functions of the cytoskeleton?

A

moves the cell
rearranges the cellular compartment
supports the plasma membrane
mechanical strength
pulls chromosomes apart during cell division
guides intracellular traffic
vesicles move using cytoskeleton as sidewalk
motor (for sperm) and crawling (WBC, fibroblasts)
muscle cell contraction

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3
Q

What happens if the cytoskeleton has defects?

A

disease can develop

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4
Q

What is RBC cytoskeleton is defective?

A

leads to anemia which can be severe and lethal

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5
Q

What disease can anemia lead to?

A

heredity spherocytosis

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6
Q

What is heredity spherocytosis?

A

RBS spherical not biconcave
fragile red blood cells burst
hemolytic anemia
cytoskeleton protein defects or deficiencies can lead to serious disease

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7
Q

Cytoskeleton filaments are consisted of multiple ______

A

protofilaments

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8
Q

What are protofilaments?

A

long linear strings of protein subunits joined end to end

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9
Q

Are protofilaments thermally unstable?

A

yes, easy to break one linear filament

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10
Q

When cytoskeleton filaments are created from multiple protofilaments bound side to side they _______ breakage by ______ ________ conditions

A

resist; ambient thermal

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11
Q

What are the three main types of filaments?

A

actin filaments
microtubules
intermediate filaments

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12
Q

What are actin filaments?

A

two stranded helical polymers of the protein actin
actin subunits are compact and globular
flexible structures 5-9 in diameter

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13
Q

What is the role of actin filaments?

A

determine the shape of cell’s surface and are necessary for whole cell locomotion, secretion, endocytosis

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14
Q

What are the properties of microtubules?

A

forms tube like structure
determine the positions of membrane enclosed organelles
directs intracellular transport

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15
Q

What do microtubules make up?

A

centrioles and mitotic spindles

cilia and flagella

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16
Q

What contributes to cystic fibrosis?

A

lack of function in cilia

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17
Q

Describe the structure of microtubules

A 
long hollow cylinders
made of tubulin subunits
long and strait 
more rigid than actin 
have centrosomes
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18
Q

What are properties of intermediate filaments?

A

provide mechanical strength
strong filament
resists mechanical stress
allows formation of hair and fingernails

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19
Q

Describe the structure of intermediate filaments

A

rope like fibers, 10 nm diamter
large heterogenous family
made of smaller subunits that are elongated and fibrous
span from one cell-cell junction to another

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20
Q

Why are intermediate filaments in a staggered organization?

A

tolerates bending and stretching

forms rope like structure

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21
Q

What does the apical surface do?

A

absorbs nutrients

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22
Q

Are microvilli on the apical or basolateral surface?

A

apical

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23
Q

What happens at the basolateral surface?

A

cells transfer nutrients to bloodstream

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24
Q

How is polarity maintained for intestinal cells?

A

maintained by actin filaments, microtubules, and intermediate filaments

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25
Q

What forms stable cell surface protrusions?

A

actin

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26
Q

What type of filament is attached to desmosomes and hemidesmosomes?

A

intermediate filaments

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27
Q

What filament forms tracks to get newly synthesized proteins to proper locations?

A

microtubules

28
Q

What builds a cytoskeleton filament?

A

protein subunit

29
Q

Cytoskeleton filaments (or polymers) are held together by weak ________

A

noncovalent interactions

30
Q

Assembly and disassembly of the cytoskeleton occurs_____

A

rapidly

31
Q

____ subunits are used for assembly fo actin filaments

A

actin

32
Q

What shape does actin subunits form?

A

helical

33
Q

Actin monomers contains binding site for _____ or _____

A

ATP or ADP

34
Q

Actin filaments are arranged ______ to generate structural polarity

A

head to tail

35
Q

What are the two ends of an actin filament?

A

plus and minus end

36
Q

What is the plus end of an actin filament?

A

fast growing or fast shrinking end

37
Q

What is the minus end of an actin filament?

A

slow growing or slow shrinking end

38
Q

ATP actin _______ and ADP actin ______

A

polymerizes (grows); disassembles (shrinks)

39
Q

What subunits form microtubules?

A

tubulin subunits

40
Q

Describe tubulin

A

hetero dimer of alpha tubulin and beta tubulin with non covalent bonds
both have binding site for one GTP

41
Q

The top beta tubulin binds to bottom _____ subunit

A

alpha

42
Q

Do microtubules have plus and minus ends?

A

yes

43
Q

What is polymerization?

A

assembly of actin or tubulin subunits into a linear polymer

44
Q

What is depolymerization?

A

removal of monomers at the ends of the polymer

45
Q

What are the steps in formation of cytoskeletal filaments?

A
  1. filament nucleation
  2. filament elongation- growth phase
  3. steady state- equilibrium phase
46
Q

What is filament nucleation?

A

process of rotation of initial aggregate, or nucleus

47
Q

What is filament elongation?

A

subunits are quickly added onto the ends of nucleated filaments

48
Q

What is the steady state?

A

rate of monomer addition equals the rate of monomer loss

49
Q

What are actin and tubulin?

A

enzymes that catalyze ATP or GTP

50
Q

What is the T form of subunit?

A

ATP/ GTP

51
Q

What is the D form of subunit?

A

ADP/GDP

52
Q

What formation does the plus end remain in?

A

T formation

53
Q

What formation does the minus end remain in?

A

D formation

54
Q

What is tread milling?

A

plus end growing while minus end is shrinking

55
Q

Where does tread milling predominate?

A

actin filaments

56
Q

What is catastrophe?

A

change from growth to rapid shrinkage

57
Q

What is rescue?

A

change from rapid shrinkage to growth

58
Q

Adding tubulin GTP produces ______ protofilaments

A

straight

59
Q

Where does dynamic instability predominates?

A

microtubules

60
Q

Is there a nucleotide binding site on intermediate filaments?

A

no

61
Q

What are keratins?

A

the most diverse group of intermediate filaments

62
Q

How many keratins are found in human epithelial cells?

A

20

63
Q

How many keratins are specific to hair and nails?

A

10

64
Q

How many distinct keratin goes are in the human genome?

A

50

65
Q

True or false? Actin monomers are microtuble subunits?

A

False

Molecular Exam 2 (13 decks)

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