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Cell Biology > Lecture 8 > Flashcards

Lecture 8 Flashcards

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AP® Biology flashcards Biology 101 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?

A

Platelets

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
Q

What forms new actin branches?

A

Arp 2/3 complex

26
Q

What stabilizes filaments?

A

capping protein

27
Q

What end to the actin filaments disassemble

A

on the (-) end at a distance from the cell surface

28
Q

What does the optical trap measure?

A

The force generated by a single myosin

29
Q

Describe what happens in a optical trap?

A
  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
Q

Describe muscle cells

A

large, tubular cells with many nuclei

31
Q

What causes the contraction of muscle cells?

A

myosin 2 motors moving along actin

32
Q

What does myosin 2 require?

A

ATP

33
Q

Both tubulins are —–

A

GTP binding proteins

34
Q

Alpha tubulin binds tightly to GTP and does not ———

A

hydrolyze the nucleotide

35
Q

Beta tubulin hydrolysis and exchanges the ———

A

the bound nucleotide

36
Q

What is bound to GTP and what is bound to GDP.

A

alpha tubulin is bound to GTP
beta tubulin is GDP bound

37
Q

What is the microtubule structure?

A

Hollow tubes made of protofilaments

38
Q

What are protofilaments made of?

A

made of tubulin dimers

39
Q

Doe microtubules have polarity

A

yes

40
Q

What is more ridged, microtubules or actin filaments?

A

microtubules

41
Q

What stabilizes the MT ends of a microtubules?

A

GTP cap

42
Q
A

Cell Biology (18 decks)

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