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Cell Biology > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

What are three types of filaments?

A

Actin, microtubules and intermediate filaments

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2
Q

What is the cytoskeleton responsible for?

A

Subcellular organization, structural integrity and movement of the cell

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3
Q

What is the structure of actin?

A

Twisted 2 strand structure 9-9nm in diameter

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4
Q

What is the structure of intermediate filaments?

A

Rope like structure - 10nm in diameter

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5
Q

What is the structure of microtubules?

A

Hollow tubes 24nm in diameter

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6
Q

What is the most abundant intracellular protein?

A

Actin

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7
Q

How many forms of actin are there?

A

Human genome encodes for 6 isoforms of acting
- four alpha actins in muscle
- B- and y-actin in non-muscle cells

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8
Q

What is a 42kDA ATPase?

A

Actin

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9
Q

What is G-Actin?

A

globular, monomeric actin

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10
Q

What is F-Actin?

A

Filament actin polymer, has structural and functional polarity, thin flexible filament

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11
Q

What is important to maintain a high concentration of monomeric actin in the cell?

A

Sequestering proteins

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12
Q

What are severing proteins?

A

Break actin filaments, necessary to breakdown existing networks

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13
Q

What are capping proteins ?

A

Cap the (+) or (-) end and stabilize the filament at that end

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14
Q

What are branching proteins?

A

Binds to an actin filament and initiates the formation of daughter filaments

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15
Q

What is the responsibility of the small protein fimbrin?

A

cross-linked filaments into bundles

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16
Q

What protein cross-links F-actin into networks

A

Filamin protein

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17
Q

What does the actin network at the cell cortex do?

A

Stabilizes the plasma membrane

18
Q

What is the roles of having a dynamic cortex?

A

actin assembly and disassembly

19
Q

What stabilizes actin filament in sarcomere of skeletal muscle?

A

Capping proteins

20
Q

What are 3 roles of actin networks?

A

Shape, move and divide cells

21
Q

What changes shape during blood clotting?

22
Q

What occurs during activation of platelets?

A

Results in reorganization of actin network, which causes a dramatic change in cell shape

23
Q

What end of the actin filaments are oriented with the (+) end?

A

towards the plasma membrane

24
Q

How do actin filaments grow?

A

They grow by addition of G-actin to the (+) end

25
What forms new actin branches?
Arp 2/3 complex
26
What stabilizes filaments?
capping protein
27
What end to the actin filaments disassemble
on the (-) end at a distance from the cell surface
28
What does the optical trap measure?
The force generated by a single myosin
29
Describe what happens in a optical trap?
1. A laser beam traps the latex bead in the center of the focus and holds the beam in position 2. The strength of the trap is regulated by the intensity of the laser beam 3. The beam intensity is increased until the myosin motor is unable to move the bead
30
Describe muscle cells
large, tubular cells with many nuclei
31
What causes the contraction of muscle cells?
myosin 2 motors moving along actin
32
What does myosin 2 require?
ATP
33
Both tubulins are -----
GTP binding proteins
34
Alpha tubulin binds tightly to GTP and does not ---------
hydrolyze the nucleotide
35
Beta tubulin hydrolysis and exchanges the ---------
the bound nucleotide
36
What is bound to GTP and what is bound to GDP.
alpha tubulin is bound to GTP beta tubulin is GDP bound
37
What is the microtubule structure?
Hollow tubes made of protofilaments
38
What are protofilaments made of?
made of tubulin dimers
39
Doe microtubules have polarity
yes
40
What is more ridged, microtubules or actin filaments?
microtubules
41
What stabilizes the MT ends of a microtubules?
GTP cap
42

Cell Biology (18 decks)

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