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BMSC 220 > Lecture #10 > Flashcards

Lecture #10 Flashcards

1
Q

What are the functions of cytoskeletal components?

A
  1. Provide structural support that determines cell shape
  2. Direct the movement of cargo and organelles within the cell
  3. Generate forces needed for cellular locomotion
  4. Position various organelles in the cell (spatial organization of cell organelles)
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2
Q

MT are assembled from the protein ______ (α/β), they are hollow, relatively rigid, tubular structures (25 nm in diameter)

A

tubulin

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3
Q

Microtubule proteins are arranged in longitudinal rows called _________.

A

protofilaments

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4
Q

Protofilaments are assembled from dimeric building blocks consisting of one α-tubulin and one β-tubulin subunit. The tubulin subunits fit ______ together and organized in a ______ array along the length of each protofilament

A

tightly, linear

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5
Q

Protofilaments are ________ (α-tubulin at one end and β-tubulin at the other) and _____ (plus end terminated by a row of β-tubulin subunits and the minus end terminated by a row of α-tubulin subunits)

A

asymmetric, polar

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6
Q

Microtubules are typically associated with additional proteins, called ?

A

microtubule-associated proteins (MAPs)

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7
Q

MAPs increase _______ and promote microtubule _______ by linking tubulin subunits together

A

stability, assembly

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8
Q

An abnormally high level of phosphorylation of one particular MAP, called tau, disables it from binding to ________ which has been implicated in Alzheimer’s disease

A

microtubules

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9
Q

MT are ______: provide mechanical support by resisting forces that might compress or bend the fiber. Distribution helps determine the ______ of that cell.

A

stiff, shape

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10
Q

MT provide means for __________ movement of organelles and molecules within the cell

A

Directed

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11
Q

Along a nerve cell _____, directed movement relies on a highly organized arrangement of microtubules and other cytoskeletal components

A

axon

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12
Q

Microtubules and actin filaments serve as tracks for a variety of _____ proteins that generate forces required to efficiently move objects within a cell

A

motor

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13
Q

Can be grouped into three broad superfamilies: ?

A

Kinesin and Dynein which move along microtubules
Myosin which moves along the actin filaments
No motor proteins are associated with intermediate filaments

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14
Q

Motor proteins move _____________ along their cytoskeletal track in a stepwise manner from one binding site to the next and undergo a series of ____________ changes that constitute a mechanical cycle which is the result of a chemical cycle (ATP hydrolysis)

A

unidirectionally, conformational

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15
Q

_______ are a superfamily of 14 related motor proteins which traverse the microtubules

A

Kinesins

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16
Q

________ are the best understood microtubular motor protein

A

Kinesins

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17
Q

A kinesin-1 molecule is a tetramer of ____ identical heavy and ____ identical light chains

A

two, two

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18
Q

The globular heads bind _________ and act as ATP-hydrolyzing, force-generating engines. Each head is connected to a neck, a rodlike stalk, and a fanlike tail that binds to _____.

A

microtubules, cargo

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19
Q

Different Kinesins share similar head structure, but differ in their ______ to carry a variety of cargos

A

tails

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20
Q

Each kinesin requires the ______ of a single ATP molecule, the __________ is proportional to the ATP concentration

A

hydrolysis, movement

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21
Q

Can walk along a microtubule for considerable ________ without falling off because one of the Kinesin heads is attached to the microtubule at any given time

A

distances

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22
Q

__________ are force-generating agents that drive the movement of cargo and organelles (mitochondria). They tend to move vesicles and organelles in an ________ direction toward the cell’s plasma membrane (towards the (+) end of MT)

A

Kinesins, outward

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23
Q

________ is a huge protein (1.5 million Dalton), and is composed of two identical heavy chains and a variety of intermediate and light chains

A

Dynein

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24
Q

In ________, the heavy chain consists of a large globular force-generating head and a microtubule-binding stalk.

A

Dynein

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25
Q

Cytoplasmic ________ moves processively along a microtubule toward the polymer’s (-) end —opposite that of most ________.

A

dynein, kinesins

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26
Q

Cytoplasmic _________ positions the spindle and moves chromosomes during mitosis; positions the centrosome and Golgi complex; and moves organelles, vesicles, and particles through the cytoplasm

A

dynein

27
Q

Nucleation of microtubules takes place rapidly inside a cell, where it occurs in association with a variety of specialized structures called ?

A

microtubule-organizing centers (or MTOCs)

28
Q

MTOCs control: ?

A

Number of microtubules
Polarity of microtubules
Number of protofilaments (13)
Time and location of assembly

29
Q

The best studied MTOC is the _________

A

centrosome

30
Q

Centrosomes contain two barrel-shaped ______ surrounded by electron dense ________ material (PCM)

A

centrioles, pericentriolar

31
Q

The ________ is a major site of microtubule initiation (nucleation) in animal cells and remains at the center of the cell’s microtubule network

A

centrosome

32
Q

A ______ ____ is another type of MTOC that forms at the _____ of the cilium or flagellum

A

basal body, base

33
Q

Basal bodies are identical in structure to _______, and can turn into centrioles and vice versa

A

centrioles

34
Q

MTOCs share a common factor, ___-______, a critical protein in microtubule nucleation

A

γ-tubulin

35
Q

The PCM serves as attachment sites for _____-shaped structures that contain γ-tubulin, the γ-tubulin ring _______. These complexes are helical array of γ-tubulin subunits where αβ-tubulin _______ assemble

A

ring, complexes, dimers

36
Q

________ are dynamic polymers subject to shortening, lengthening, disassembly, and reassembly

A

Microtubules

37
Q

Some microtubules are highly ______ such as those in cilia an neurons, while others are subject to ________ such as those forming the cytoskeleton or mitotic spindle

A

stable, disassembly

38
Q

Microtubules stability is determined by microtubule ________ proteins: microtubules associated proteins (MAPs); proteins known as +TIPs which bind to the ____-end of growing microtubules; ________, an enzyme that severs microtubules into shorter pieces

A

interacting, plus, Katanin

39
Q

Disassembly can be initiated by:
____________ modifications (attachment of multiple glutamates to tubulin C-terminus)
_____ temperature
_________ pressure
elevated _____ concentration
variety of chemicals (nocodazole)

A

posttranslational, cold, hydrostatic, Ca2+

40
Q

The microtubules of the cytoskeleton are normally subject to depolymerization and repolymerization as the _________ of the cell change from one time to another

A

requirements

41
Q

During _______ of tubulin dimers:

A GTP molecule is bound to the β-tubulin subunit (β-tubulin is a structural protein and a GTPase). GTP is hydrolyzed to GDP after the dimer is incorporated, and the resulting GDP remains bound to the assembled polymer

A

assembly

42
Q

During _______ of tubulin dimers:

The dimer enters the soluble pool, the GDP is replaced by a new GTP. This nucleotide exchange “recharges” the dimer, allowing it to serve once again as a building block for polymerization.

A

disassembly

43
Q

Growth or shrinkage of a microtubule depends on the state of the tubulin dimers at the ____ end

A

plus

44
Q

Growth or shrinkage of a microtubule depends on the state of the tubulin dimers at the plus end:
1. The ____ consists of an open sheet containing tubulin – GTP subunits.
2. The tube begins to _____, forcing hydrolysis of the bound GTP.
3. The tube has _____ to its end, leaving only tubulin – GDP subunits (GDP-tubulin has a different conformation than GTP-tubulin, which makes them less able to fit into a _________).
4. The strain from the GDP-tubulin at the plus end causes a catastrophic _______.

A

tip, close, closed, protofilament, shrinkage

45
Q

______: hairlike, sometimes motile organelles and project from the surface of a variety of eukaryotic cells

A

Cilia

46
Q

There is usually one _______ _____ (primary cilium) per eukaryotic cell. This cilium acts as a sensory organelle, monitoring mechanical and chemical properties of the extracellular fluid

A

nonmotile cilium

47
Q

______ ____ usually occur in large numbers on a cell’s surface, with a coordinated beating activity. These cilia move fluid and particulate material through tracts (i.e., respiratory)

A

Motile cilia

48
Q

_______ cells: nonmotile cilia act as flow sensors

A

Kidney

49
Q

______ cells: motile cilia cause flow of fluids

A

Trachea

50
Q

_______ typically occur singly or in pairs, and exhibit a variety of beating patterns (waveforms), depending on the cell type.

A

Flagella

51
Q

Cilia and flagella have a membrane that is _________ with the plasma membrane.

A

continuous

52
Q

________: is the core of the cilium and contains an array of microtubules that runs longitudinally through the entire organelle

A

Axoneme

53
Q

The _______ of a motile cilium or flagellum consists of nine peripheral doublet microtubules surrounding a central pair of single microtubules (known as the 9 + 2 array)

A

axoneme

54
Q

Each axoneme contains:
1. Peripheral doublets with an A tubule (_______ microtubule) and a B tubule (_______ microtubule)
2. Central tubules enclosed by the central ______, connect to the A tubules by a set of radial ____.
3. Doublets are connected to one another by an ________ bridge
4. Inner arm and an outer dynein arms that project from the ___ tubules

A
  1. complete, incomplete
  2. sheath, spokes
  3. interdoublet
  4. A
55
Q

A _________ section reveals the continuous nature of the microtubules and the discontinuous nature of the other elements

A

longitudinal

56
Q

A cilium or flagellum emerges from a _____ ____

A

basal body

57
Q

If a cilium or flagellum is sheared from the surface of a living cell, a new organelle is __________ as an outgrowth of the basal body

A

regenerated

58
Q

The Mechanism of Ciliary and Flagellar Locomotion:

  1. The dynein arms anchored along the __ tubule of the lower doublet attach to binding sites on the __ tubule of the upper doublet.
  2. Dynein undergoes a conformational change (power stroke) that causes the ____ doublet to slide toward the basal end of the _____ doublet.
  3. The dynein arms have detached from the __ tubule of the _____ doublet.
  4. The arms have reattached to the _____ doublet so that another cycle can begin.
A
  1. A, B
  2. lower, upper
  3. B, upper
  4. upper
59
Q

_____ forms an elastic linkage connecting adjacent doublets. These limit the extent that adjacent doublets can slide over one another

A

Nexin

60
Q

Sliding on one axoneme side alternates with sliding on the other side so that a part of the cilium or flagellum bends first in ___ direction and then in the _________ direction.

A

one, opposite

61
Q

At any given time, the _______ arms on one side of the axoneme are active, while those on the other side are inactive

A

dynein

62
Q

________: a set of seemingly unrelated diseases that all result from primary cilia defects

A

Ciliopathies

63
Q

Ciliopathies include:
1. Polycystic Kidney Disease (PKD) is a major cause of _______ ______ in adults → fluid filled cysts are formed on the surface of kidneys because of mutations in PKD1 and PKD2 located on the primary cilia (which monitor urine flow)
2. Bardet-Biedl Syndrome (BBS) → developmental syndrome caused by abnormal _______ ______ into the primary cilia

A

kidney failure, protein trafficking

BMSC 220 (22 decks)

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