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Cell Bio 2 > Exam 3 - Andreas Slides > Flashcards

Exam 3 - Andreas Slides Flashcards

Understand Andreas slides for Cell Bio 2. LETS DO THIS!

1
Q

What are the three types of cytoskeletal fibers?

A
  1. Microtubule (tublin)
  2. Actin filament
  3. Intermediate filament (only in animal cells, 6 different types of proteins)
    - Mutations of microtubules and actin basically will kill you because they are so important for life. - Fibers made of polymerized protein.
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2
Q

What do actins do?

A
  1. Bind nucleotides (ATP) 2. Forms tight helical filaments (F-actin) from globular domains (G-actin) 3. Polar polymer (pointed and barbed end) Like a pine tree 4. Essential for all Eucaryotic cells (Cell motility/cytokinesis/muscle contraction) 5. The most abundant protein in the world
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3
Q

What do microtubules do?

A
  1. GTP binding site 2. Forms hollow tubes -> alpha-beta-tubulin dimer 3. Polar polymer (plus and minus end) 4. Essential for all Eucaryotic cells (mitosis/trafficking between cell center and periphery) 5. Similar proteins in some Bacteria (EG. FtsZ)
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4
Q

What do Intermediate Filaments do?

A
  1. No nucleotide binding site 2. Six different classes -> bundles of alpha helical coiled-coil proteins. 3. Filaments have no polarity 4. Metazoan (animal) cells (cell structure and shape/stability) 5. Some similar structures found in bacteria 6. Involved in a variety of diseases (mutations all over the place)
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5
Q

Describe Myosins (in Actin)

A

Directionality: Mostly barbed end Speed: 0.5-1micrometer/sec Force: 1-5 pN Location: Muscle, cytoplasm, cell periphery

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6
Q

Describe Dyneins (In Microtubules)

A

Directionality: Minus-end Speed: Unknown Force: 1-5 pN Location: Axonemes (flagella cilias) cytoplasm, spindle, axons

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7
Q

Describe Kinesins (In microtubules)

A

Directionality: Most plus-end (N-term) some minus-end (C-term) Speed: 0.2-2 um/s Force: 1-5 pN Location: Axons, spindles, cytoplasm

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8
Q

Why is the force the same across the molecular motors?

A

They all consume the same energy source = ATP

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9
Q

Which cytoskeletal system does NOT support molecular motors, and why?

A

Intermediate Filaments because they are non-polar (no directionality)

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10
Q

Why would you want a protein to sever the middle of a MT?

A
  1. Katanin frees up MTs that can be moved to cilia and axons. 2. It also helps to turn over MTs rapidly.
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11
Q

Why would you want a protein to remove the GTP cap of a MT?

A

Microtubules need to shrink, e.g. during chromosome segregation in mitosis. (EG. MCAK

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12
Q

What is XMAP215?

A

A stabilizing (+) end binding protein that catalyzes the addition of multiple individual tubulin subunits.

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13
Q

What is CLIP170?

A

A MAP that both stabilizes (+) TIPs and binds to endocytic vesicles.

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14
Q

The (+) end of a microtubule is?

A

More dynamic than the (-) end.

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15
Q

What is MTOC?

A

Microtubule organizing center

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16
Q

There are more MTs during mitosis but they are shorter. Why?

A

Less stabilizing MAPs and more gamma-TuRC

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17
Q

(+) end cap regulates ___________.

A

stability of MT

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18
Q

Most stable conformation of protofilaments of GTP tubulin is ______.

A

Straight

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19
Q

Most stable conformation of protofilaments of GDP tubulin is ______.

A

Curved

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20
Q

What happens when the GTP cap is lost?

A

Protofilaments curl outward leading to individual curved protofilaments breaking off the microtubule and depolymerizing.

21
Q

What is MAPs?

A

Microtubule Associated Protein(s)

22
Q

What does Human Tau40 do?

A
  1. Non-motor MAP 2. Highly flexible/no secondary structure 3. Effective modulator of microtubule dynamics
23
Q

MAPs can do what to MTs?

A
  1. Destabilize 2. Speed up microtubule turnover
24
Q

What does MCAK (GAP) do?

A

Removes GTP cap from growing microtubule to cause disassociation of tubulin subunits = shortening.

25
Q

What does Katanin do?

A

Severs intact MT which helps with MT turnover and transfer of MTs.

26
Q

What does colchicine (drug) do?

A

Sequesters dimers. - Sometimes subunits of MT are free to polymerize, but the drug stops (binds with) subunits to prevent polymerization.

27
Q

How do (+) TIPs stabilize the (+) tip?

A

+TIP proteins bind to the polymerizing + end of microtubule.

28
Q

Describe the MT polarity in Fibroblast, Epithelial cells, and neurons.

A
29
Q

Transport from the ER to the Golgi is what? (Directionality)

A

Retrograde (+ end to - end)

30
Q

Transport from the Golgi to the Plasma mebrane is what? (Directionality)

A

Anterograde (- end to + end)

31
Q

What is the Pulse-chase experiment?

A

Things beginning in the ER travel to Golgi, then to Plasma membrane.

  • Temperature sensitive VSVG mutant begins to traffic at permissive temp.
32
Q

Briefly describe Kinesins and its directionality.

A
  1. MT-based Motor Protein
  2. Plus AND minus-end directed motors (BUT mostly plus end)
33
Q

Briefly describe Dyneins and its directionality.

A
  1. MT-based motor protein.
  2. Minus-end directed motors
34
Q

How are cargo loaded onto motors?

A

Tail domain binds cargo via adaptor protein.

35
Q

Plus-end Kinesin starts at ______ and minus-end starts at ______.

A

N-terminus, C-terminus

36
Q

Retrograde transport is towards _______ while Anterograde is towards ________.

A

Cell body, synapse

37
Q

What is the driving force of dimerization in Kinesin-1 (a homodimer)?

A

Hydrophobic interactions, alpha-helical coiled-coil formation, and leucine zipper.

38
Q

Which regions in a kinesin motor domain are controlling microtubule-binding?

A

The ATP-binding site (part of switch-1), The switch-II region, and the neck-linker region.

39
Q

What are actin stressfibers?

A

Contractile bundles of actin filaments and myosin that are anchored to focal adhesions at the plasma membrane and function in cell adhesion.

40
Q

What are Hemidesmosomes?

A

Anchoring junctions: form rivet-like links between cytoskeleton and extracellular matrix components such as the basal laminae that underlie epithelia. Like desmosomes, they tie to intermediate filaments in the cytoplasm, but in their transmembrane anchors are integrins rather than cadherins.

41
Q

What are desmosomes?

A

Anchoring function: Rivets through the plasma membrane of adjacent cells. Cadherin molecules form the actual anchor by attaching to the cytoplasmic plaque.

42
Q

What are adherens junctions?

A

Anchoring Junction: Share the characteristic of anchoring cells through their cytoplasmic actin filaments. Composed of cadherins and integrins.

43
Q

What do cadherins anchor to?

A

Other cells

44
Q

What do integrins anchor to?

A

Extracellular matrix

45
Q

What do tight junctions do?

A

Act as barriers that regulate the movement of water and solutes between epithelial layers. Classified as a paracellular barrier: not having directional discrimination (movement is largely dependent upon solute size and chare)

46
Q

Why are tight junctions AKA occluding junctions or zonula occludens?

A

This junctional complex is only present in vertebrates. (Septate junctions occur in invertebrates)

47
Q

What are communicating (GAP) junctions?

A

Allow for direct chemical communication between adjacent cellular cytoplasm through diffusion without contact of the extracellular fluid.

48
Q

What are connexin proteins?

A

A protein found in gap junctions and six of them interact to form a cylinder with a pore in the center. Goes across the cell membrane and interacts with an adjacent cell connexon (6 connexins) to form a gap junction channel.

Cell Bio 2 (21 decks)

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