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BIOL-3221 > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

What are the three filament structures of the cytoskeleton

A
  • Microtubules (direct movement within the cell)
  • Actin filaments (support cell shape. mobility and intracellular transport)
  • Intermediate filaments (provide structural support and mechanical strength
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2
Q

What is the role of the cytoskeleton

A
  • Skeletal system of a eukaryotic cell
  • Structural support, cell shape maintenance
  • Intracellular transport
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3
Q

How are microtubules different from actin filaments and intermediate filaments

A
  • Microtubules have GTPase activity
  • Actin filaments have ATPase activity
  • Intermediate filaments have no enzymatic activity
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4
Q

Explain the dis/assembly of tubulin dimers

A
  • A GTP molecule + ß-tubulin, GTP -> GDP when the dimer is incorporated & GTP remains bound
  • Dis: GDP is replaced with a new GTP, which allows polymerization
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5
Q

What major groups are associated proteins are linked to microtubules, intermediate filaments and actin filaments

A
  • MAPs (microtubule- associated tubules) for microtubules, plakins for intermediate filaments and actin-binding proteins for actin filaments
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6
Q

What is the basic structure of microtubules

A
  • Hollow, rigid tubular structure with 13 protofilaments with alpha and ß-tubulin arranged in a circular pattern
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7
Q

What is the polarity of microtubules

A
  • The plus end is the ß-tubulin and the minus-end is the alpha-tubulin
  • This is critical for intracellular transport
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8
Q

What is the function of MAPs?

A
  • MAPs increase the stability of microtubules and promote their assemble by linking subunits together
  • High levels of phosphorylation in Tau = Alzheimer’s disease
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9
Q

What is the function of kinesins and dyneins

A
  • They are motor proteins that move cargo along microtubles
  • Kinesins move towards the plus end and the dyneins move towards the minus end
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10
Q

Describe the structure of kinesin

A
  • They’re tetramers with two heavy chains and two light chains.
  • The globular heads bind microtubules and hydrolyze ATP for nrg
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11
Q

What happens when there are motor protein defects

A
  • They can result in neurological diseases bcos of sucky transport
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12
Q

What is a microtubule-organizing center (MTOC)

A
  • They’re cellular structures that nucleate and organize microtubules, such as centrosomes in animal cells
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13
Q

Centrosome structure

A
  • A pair of centrioles surrounded by a pericentriolar material (PCM) to nucleate the MT growth
  • Centrioles help to organize the PCM and contribute to the formation of cilia and flagella
  • They position themselves to direct microtubules, influencing of organelles and proteins
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14
Q

What is the function of y-tubulin ring complex (y-TuRC)

A
  • The y-TuRc is within the pericentriolar material
  • Acts as a template for microtubules nucleation, specifying the minus end
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15
Q

How do microtubules contribute to mitotic spindle formation

A
  • During cell division, they reorganize to form mitotic spindle, which separates chr into daughter cells
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16
Q

What is the structural polarity of actin filaments

A
  • Actin filaments have fast-growing (+) end (barbed end) and a slow-growing (-) end (pointed end) that’s critical for directional growth and assembly
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17
Q

What is the core structure of cilia and flagella

A
  • Axoneme with a 9+2 microtubule arrangement
  • Nine outer doublets with two central singlet microtubules
  • They are anchored on the basal body (MTOC) of their assembly
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18
Q

What is the primary fxn of cilia and flagella

A
  • Cilia move fluid, mucus or particles over a cell’s surface (back-and-forth beating motion)
  • Flagella are used for locomotion, propelling cells like sperm (in a whip-like motion)
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19
Q

What protein is responsible for cilia and flagella movement

A
  • Dynein, generates force for sliding of microtubules in the axoneme
  • ATP gives dynein nrg to drive the sliding of microtubules, which causes the bending motion of cilia and flagella
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20
Q

What is the structural difference between basal body and axoneme

A
  • The basal body has 9+0 arrangement
  • The axoneme has 9+2 arrangement
21
Q

What are radial spokes in the axoneme

A
  • Radial spokes are protein complexes extending from the outer doublets to the central pair to coordinate cilia and flagella movement
22
Q

What is the role of nexin in ciliary and flagella motion

A
  • It links adjacent microtubules doublets and helps regulate sliding, converting it into bending movements
23
Q

Cilia and flagella assembly

A
  • IFT proteins => IFT particles => IFT trains
  • They carry cargo proteins out for assembly, inhibition of IFT prevents cilia and flagella assembly
24
Q

Flagella and cilia locomotion

A
  • Dynein anchors then a-tubule of the lower doublet and the b-tubule of the upper doublet
  • Lower end slides towards the basal end of the upper end
  • dynein detached from thr upper doublet, reattached and another cycle begins
25
Q

Assembly process of intermediate filaments

A
  • They lack polarity & enzymatic activity and they are not involved in intracellular transport
26
Q

Two types of intermediate filaments

A
  • Keratin (epithelial cells)
  • Neurofilament (cytoplasm of neurons)
27
Q

What is the role of intermediate filaments(keratin) in cell-cell junctions

A
  • They link to desmosomes which will anchor cells to each other and the ECM
28
Q

IF architecture

A
  • Monomer: pair of globular terminal domains separated by a long å-helical region
  • monomers => parallel dimers
  • Dimers => antiparallel and staggered tetramers
  • 8 tetramers = a unit
29
Q

What are actin-binding proteins (ABPs)

A
  • They regulate actin filaments, controlling nucleation, elongation, capping and severing to adapt the cytoskeleton to cellular needs
30
Q

What is treadmilling

A
  • The point during simultaneous addition of actin monomers at the barbed end and a loss at the pointed end, where both reactions are balanced
31
Q

Actin cell mobility

A
  • Actin filaments form structures like lamellipodia, enabling cells to crawl by pushing the plasma membrane forward
32
Q

Actin and myosin relation

A
  • The actin filaments are like tracks for the myosin motor proteins
  • They help with cytokinesis and muscle contraction
33
Q

What is the difference between lamellipodia and filopodia

A
  • lamellipodia: broad sheets made from dense actin networks
  • Filopodia: thin, fingers made from bundled actin filaments
34
Q

Functions of focal adhesions in cell motility

A
  • They connect actin cytoskeleton to the ECM
35
Q

Function of myosin

A
  • It is a motor protein that uses ATP hydrolysis to move along actin filaments
  • ATP binding causes myosin to release actin, ATP hydrolysis causes myosin to reposition its head for the next power stroke
36
Q

Structural components of myosin II

A
  • It has a globular head (ATPase activity), a lever arm (regulatory light chain), and a long tail (for dimeration and filament formation)
  • The tails point to the center and the heads point outside (bipolar)
  • They generate contractile forces at the basal end of the cell = retraction/propulsion during cell motility
37
Q

Unconventional myosin

A
  • (Myosin I, V & VI)
  • V: moves in a hand-over-hand fashion to the kinesin so two head are on the filament at all times
  • They’re localized within hair cells of the inner ear
  • VI: moves towards the pointed end of the actin filaments (reverse)
38
Q

What is the basic unit of muscle contraction

A
  • The sarcomere, a repeating unit of myofibrils with actin (thin) and myosin (thick) filaments
39
Q

What are the roles of Z, A and I bands in sarcomeres

A
  • Z line: Anchors thin filaments and marks sarcomere boundaries
  • A: contains thick filaments and regions that overlap with thin filaments
  • I: contains only thin filaments
    H zone: only thick filaments
40
Q

What triggers muscle contraction

A
  • Ca2+ ions bind to troponin, causing tropomysoin to move (expose actin binding sites for myosin)
  • Sliding filament model: thin ones slide past thick ones (sarcomere shortens, each filament is still the same length)
41
Q

How is ATP replenished in muscle cells during contraction

A
  • Creatine phosphate
  • Glycolysis
  • Oxidative phosphorylation
42
Q

Excitation-contraction coupling

A
  • Contact at the neuromuscular junction that shortens the sarcomere
  • AP in the muscles are propagated by transverse (T) tubules that terminate where Ca2+ is stored (sarcoplasmic reticulum)
43
Q

What is the purpose of studying muscle biometrics

A
  • To understand how muscles convert biochemical nrg to mechanical work
  • Key propertied of muscles studied is elasticity, allowing muscles to store/release nrg during movement
44
Q

How do researchers apply muscle biometrics in technology

A
  • Electromyography: measures AP within muscle tissue
  • Fucntional electrical stimulation: stimulates/mimis muscle activity
45
Q

name the three classes of actin-binding proteins

A
  • Nucleating proteins: promote actin polymerization (Arp2/3 complex)
  • Severing proteins: cut actin filaments into smaller fragments to prevent further polymerization (gelsolin)
  • Capping proteins: stabilize filament ends they bind to the (+/-) end oif the filament to prevent the addition/loss of actin monomers (CapZ)
46
Q

How do cross-linking proteins contribute to actin organization

A
  • They bind multiple filaments = 3-D networks that give structural integrity (filamin)
47
Q

What is the role of RHO GTPases in cellular motility

A
  • They regulate actin dynamics by promoting lamellipodia, filopodia or stress fibers to coordinate cell movement
48
Q

What are the main components of the bacterial cytoskeleton

A
  • FtsZ, CreS, ParM (homologous of tubulin and actin)
49
Q

The roles of bacterial components

A
  • FtsZ: forms a contractile ring at the site of cell division - septum formation in binary fusion
  • ParM: segregates plasmids during cell division by polymerizing into filaments that push plasmids to opposite poles of the cell
  • CreS: polymerizes proximal to the membrane, plays a key role in cell shape

BIOL-3221 (6 decks)

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