Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cell Biology Exam 3 > Chapter 17: The Cytoskeleton Part II > Flashcards

Chapter 17: The Cytoskeleton Part II Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Actin

A
  • actin filament -> polymers of actin
  • mnost abundant protein in nearly all cell types
    -maintain cell shape and movements that involve cell outer membtane
  • actin filaments interact with actin-binding proteins that enable filaments to serve various functions
  • has movement driven with motor proteins (like microtubules!!)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

cytoskeleton filaments

A
  • constructed from smaller protein subunits
  • smaller soluble subunits & large filamentous polymer
    -dynamic and adaptable
  • formation of protein filaments from smaller protein subunits allows regulated filament assembly and dissassembly to reshape to cytoskeleton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Actin filaments

A
  • thin, flexible protein with structurally distinct ends
  • two stranded helix with twists, twists of identical globular monomers, they “face” same direction
    -lateral interaction prevent separation
  • shorter than microtubules
  • grow by addition of monomers on either end (plus side faster)
  • similar to microtubules: such as polarity with plus and minus end
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Actin polymerization

A
  • actin monomers in cytosol carry ATP
  • ATP hydrolyzed to ADP soon after assembly into growing filament
  • ADP molecules remain trapped within actin filament, unable to exchange with ATP until actin monomer carries them dissociates from filament
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Actin “treadmilling”

A
  • rate of monomer addition = rate of monomer loss (remains one length)
  • causes move through of actin from plus end to minus end
  • if actin monomers added to plus end faster than ATP is hydrolyzed, then plus end grows
  • if ATP hydrolyzed faster than monomers added, the minus end loses (ADP-actin destabilizes, loose structure)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Microtuble dynamic instability

A
  • switching between polymerization and depolymerization
  • undergo rapid remodeling
  • crucial to function (division)
    -stems from intrinsic capacity of tubulin dimers to hydrolyze GTP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Growing microtubule

A
  • grow since bound to GTP
  • GTP-tubulin combo hydrolyzes to GDP after dimer is added
  • rapid polymerization, tubulin dimers bind faster than GTP hydrolyze
  • this makes end completely GTP-tubulin dimers, creates GTP cap(packs efficiently and grows)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

shrinking microtubule

A
  • hydroylzed GTP to GDP + phosphate
  • protofilaments composed of GDP tubulin pack loosely, favoring dissassembly
  • once depolymerization starts, it continues
  • dissasssembled GDP tubulin in cytoplasm (exchange bound GDP for GTP so they can be added to growing microtubule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

microtubule building-

A
  • microtubules grow when bound to GTP, but when GTP is hydrolyzed to GDP microtubules shrink
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

nucleation

A
  • occurs in actin and microtubules
  • the process by which atoms or molecules come together to form a new phase or structure.
  • rate limiting step in polymerization
    -helical polymer stabilized by multiple contacts between adjacent subunits
  • (in actin, two actin molecules bind realtively weakly to each other, third actin creates trimer to make entire group more stable)
  • further monomer addition can take place for trimer, which therefore acts as nucleus for polymerization
  • slow assembly from lag phase(can be reduced or abolished)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Lag phase

A
  • seen during polymerization
  • when cells are adjusting to a new environment before starting exponential growth
  • reduced or abolished entirely by adding premade nuclei, such as fragments of already polymerized microtubules or actin filaments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Course of polymerization

A
  • assembly of protein into a long helical polymer such as a cytoskeletal filament or bacterial flagellum
    -lag phase(lower polymers and low time)
  • growth phase (increasing polymers over time)
  • equilibrium phase (no net change, higher polymers and time)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lag phase

A

corresponds to time taken for nucleation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

growth phase

A

occurs as monomers add to exposed ends of growing filament, causing filament elongation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

equilibrium phase

A

steady phase, reached when growth of polymer due to monomer addition precisely balances the shrinkage of the polymer due to disassembly back to monomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Nucleatin of Actin

A
  • involves ARP complex, Formins
  • makes different types of actin filaments
  • typically occurs in response to extracellular signals and is catalyzed by actin related proteins(ARP complex)nucleating at minus end, allowing rapid elongation at plus end
17
Q

Formin

A
  • proteins
  • actin elongation mediated by formins
  • forma dimeric complex that can nucleate new actin filaments
  • nucleates growth of straight, unbranched filaments that form parallel bundles and remain associated with rapidly growing plus end as it elongates
  • maintains binding to one of the two actin subunits at the plus ends
  • formins connect indirectly to plasma membrane
18
Q

ARP complex

A
  • actin related proteins
  • contrasts to formins
  • nucleates and remains bound to minus end and form branched webs of actin
19
Q

Actin Cell Movement

A
  • depends on polymerization and depolymerization of actin in response to signals
  • actin nucleatin influences the type of protrusions formed at leading and trailing edge (involved cell crawling)
20
Q

Cell crawling

A
  • cell sends out protrusions at its front/leading edge
  • thes protrusions adhere to the surface over which cell is crawling
  • rest of cell drags itself forward by traction on points of anchorage
21
Q

ARP promotion

A
  • promotes formation of branched actin filaments in lamellipodia (filaments produce side branches; web undergoes addition at leading edge and disassembly further back, pushes lamillipodium forward)
22
Q

Actin-binding proteins

A
  • bind to actin monomers in cytoplasm (regulate when/where actin filaments form and grow; ARP and formins promote actin polymeriztion)
  • controlled by extracelular signal molecules (act through cell surface receptor proteins, activate signal pathways; coverage on group relaed monomer GTPases)
23
Q

Cell motility

A

-cell polymerization here involes activation of different Rho members at cell opposite ends that give motility, allows movement in particular direction
involves cell signaling(changes in actin cytoskeleton)
- have receptor proteins that act on intracellular targets (Rac, Rho)

24
Q

Rac and Rho

A
  • GTP binding proteins involved in cell motility
  • molecular swtiches: control intracellular processes by cylcing between active GTP-bound state and inactive GDP bound state
25
Q

Rho protein family

A
  • alter organization of actin filaments
  • one triggers bundling of actin filaments and activation of formin proteins (promotes filopodia formation)
  • one activates nucleation promoting factors, stimulate ARP complexes that iduce lamellipodia formation
  • one (MAJOR) bundles actin filaments with motor proteins to form contractile fibers
26
Q

Actin motor proteins

A

thymosin and myosin

27
Q

thymosin

A

bind and prevent addition to actin filaments until needed (contribute to regulation)

28
Q

myosin

A

in family or motor proteins that bind to and hydrolyze ATP; provides energy for actin filament to move forward toward plus end)

29
Q

various actin binding protein functions

A

actin bundling that holds parallel bundles together, cross-links together to support membrane, and severing proteins to create shorter lengths

30
Q

Muscle contraction

A
  • triggered by sudden rise in cytosolic Ca2+ (released to ion channels in sarcoplasmic reticulum membrane; often relays messages from cell exterior to cell interior
  • small, bipolar myosin II filament can slide two actin filaments of opposite orientation past each other(generates strong contractile force!)
  • myosin II head group walks toward the plus end of the actin filament with which it interacts; multiple myosin molecules required to generate movement
31
Q

muscle myosin in myosin II subfamily

A

-muscle contraction depends on these interacting filaments of actin and myosin
- has dimer proteins: two globular ATPase heads at one end and single coiled coil tail at other
- clusters of myosin II bind through tail to form bipolar myosin filament(heads project outwards)

32
Q

structures of muscle contraction

A
  • skeletal muscle fibers formed by fusion of many separate cells(bulk made of myofibrils)
33
Q

myofibrils

A
  • contractile elements of muscle cell, actin filaments and myosin II filaments arranged in organized structure call sacromeres!
  • myosin II in middle, actin on outer edges extending inward
34
Q

sacromere

A
  • consits of ordered array of parallel and partly overlapping thin(actin, light bands) and thick filaments(myosin, dark bands)
  • attachment of each thin filament occurs at Z-disc/line (no myosin)
35
Q

Detailed description of rise in Ca2+ for muscle contraction

A
  • activates molecular switch of accesory proteins
  • includes tropomyosin and toponin to control skeletal muscle contraction
  • in resting muscle troponin I pulls tropomyosin out of the helix therby blocking myosin binding site on actin
  • binding of Ca2+ to troponin C forces conformational change diriving the tropomyosin complex deep with the actin helix exposing the myosin binding site on actin
  • single passed rapidly
36
Q

Mutant keratin

A
  • skin more prone to blistering
  • rare human genetic disease, epidermolysis bullosa simplex
  • keratin genes intefere with formation of keratin filaments in epidermis
37
Q

Anti-mitotic drugs

A
  • can control caner that target mitotic spindle
  • some drugs destabilize microtubules by interfering with polymerization of tubulin dimers
  • cause inappropriate proliferation tumor cells to die
  • at expense of death of healthy tissue as well
38
Q

Ciliary dyenin

A
  • left-right asymmetry caused by mutations in these
39
Q

neutrophils

A
  • migrate out of blood into infected tissues when small molecules released by bacteria (engulf them when found)

Cell Biology Exam 3 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions