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Block II > Cell Anatomy - Cytoskeleton > Flashcards

Cell Anatomy - Cytoskeleton Flashcards

1
Q

What is the cytoskeleton

A

System of protein filaments in the cytoplasm that gives a cell shape and the ability for directed movement

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2
Q

What are the three types of protein filaments

A

Microtubules
Actin filaments
Intermediate filaments

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3
Q

Rank the protein filaments from most –> least flexible

A

Intermediate
Actin
Microtubules

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4
Q

General properties - filament assembly

A

Self-assemble from small subunits- allows for rapid assembly/disassembly
Held together by weak, non-covalent bonds

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5
Q

How are filaments both stable and dynamic?

A

breaking a filament in the middle requires breaking many bonds, but requires little energy to remove subunits from the ends

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6
Q

What regulates the assembly of filaments?

A

Accessory proteins

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7
Q

Microfilaments dtructure

A

Globular actin monomers
Actin monomers bind ATP –>
Assemble to form a filament
2 parallel protofilaments twist to form a R helix

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8
Q

Do filaments have polarity?

A

yes

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9
Q

What end do filaments grow from?

A

The plus end

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10
Q

What part of the cell are microfilaments usually found?

A

Near the periphery

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11
Q

Microfilaments main functions:

A

Determine shape of the cell’s surface
Facilitate whole cell locomotion

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12
Q

What facilitates the ‘crawling’ of microfilaments

A

Actin polymerization

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13
Q

Microtubules: structure

A

-Globular tubulin subunits
-Tubulin monomers bind to GTp
-Alpha and beta monomers form dimers
-Protofilaments form hollow cylinder

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14
Q

Do microtubules have polarity

A

Yes. Subunits point in 1 direction, protofilamenst are parallel, grow from plus end

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15
Q

Where are microtubules usually located?

A

-Made in the microtubule organizing center (centrosome)
-Located near the nucleus

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16
Q

Main function of microtubules

A

-Determine the position of membrane-enclosed organelles
-Direct intracellular transport

17
Q

Structure of intermediate filaments

A

-Rope-like
-assembled from subunits (keratins, neurofilaments, lamins)
-No associated nucleotide
-Alpha helical subunits dimerize into tetrameric subunits
-tetramerics pack together to form protofilament
-8 protofilaments form intermediate filament

18
Q

Are intermediate filaments polar?

A

No

19
Q

Location of intermediate filaments

A

Cells that are subject to mechanical stress

20
Q

How are accessory proteins related to the cytoskeleton?

A

-Crosslink or bundle fibers
-Nucleate filament polymerization
-Cap/block polymerization
-Sever filaments

21
Q

What are motor proteins

A

-Type of cytoskeleton binding protein
-Move molecules and enclosed organelles in the cell
-Generate the force required for contraction, ciliary movement, and cell division

22
Q

How do motor proteins move

A

Use ATP hydrolysis to generate mechanical force that allows them to walk along microtubule and microfilaments

23
Q

What are the major types of motor proteins

A

Myosin
Kinesin
Dynein

24
Q

What are the filaments associated with each motor protein

A

Myosin - microfilaments (actin)
Kinesin - microtubules
Dynein - microtubules

25
Q

Structure of molecular motors

A

-head region - binds and hydrolyzes ATP
-Tail region - binding site for ‘cargo’

26
Q

Kinesin - structure

A

2 globular head domains

27
Q

Dynein - structure

A

2 or 3 main proteins plus a variable number of associated polypeptides

28
Q

What is the largest and fastest molecular protein

A

Dynein

29
Q

Kinesis ‘walks’ towards which end of the filaments

A

The plus end

30
Q

Kinesis - how it moves

A

Hydrolysis of ATP changes conformation of protein, allowing it to walk along the microtubules

31
Q

Dynein - how it moves

A

Nucleotide hydrolysis + MT binding and unbinding + force generating conformational change
Power stroke also driven by ATP hydrolysis, causes head to rotate and generate a step

32
Q

Dynein walks towards which end of the microtubule?

A

The minus end

33
Q

Kinesin - funtion

A

Bring cargo to periphery of cell
Organelle positioning
Axonal transport
Mitosis

34
Q

Dynein - funtion

A

Bring cargo to center of the cell
Cilia beating
Vesicle transport
Mitosis

35
Q

Subunits of microfilaments

A

Actin

36
Q

Subunits of microtubules

A

Tubulin

37
Q

Subunits of intermediate filaments

A

keratin

38
Q

Microfilaments bind…

A

ATP

39
Q

Microtubules bind…

A

GTP

Block II (28 decks)

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