Cell Biology

actin

filament that determines shape of cell surface, aids in whole cell locomotion, and forms contractile ring in mitosis

microtubules

filament that determines position of organelles, direct intracellular transport, and forms miotic spindle

intermediate filaments

filament that provides mechanical stength to cells

actin

filament that composes the contractile ring

cortex

where is actin mostly found, right below plasma membrane

G-actin, F-actin

Two forms of actin

ATP, ADP when in filament

What does G-actin contain?

Nucleation

what is the lag phase of actin formation?

trimer

What is the oligomeric state of an actin nucleus?

when critical concentration equals free actin monomer

When does an actin filament reach equailibrium?

[free monomer] is less than < critical concentration

When does actin depolymerization occur?

[free monomer] is greater than > critical concentration

When does actin polymerization occur?

When critical concentration of minus end is greater than free monomer and the critical concentration of plus end is less than free monomer

When does treadmilling occur?

protein regulation

Why is 50% of actin in globular form even though its above the critical concentration???

Thymosin

Keeps G-actin from binding to filament, prevents growth

Profilin

facilitates addition of g-actin, grows filament

Arp 2/3 and Fromin

Examples of Actin nucleators

Arp 2/3

Actin nucleator that enables branched actin at 70 degree angle

the minus end

Where does Arp 2/3 sit on actin?

Formin

Actin nucleator that forms long, unbranched actin filaments

stress fibers, filopodia, contractile ring

Long unbranched actin examples? (for formin)

profilin

What binds to the whisker domain of formin to bring actin near?

Tropomodulin and CapZ

Examples of actin capping proteins?

CapZ

Capping protein on the plus end of actin

Tropomodulin

Capping protein on the minus end of actin

CapZ

Actin Capping protein near the Z-disc of sarcomere

Cofilin

protein which forces actin to breakdown by overtwisting it, binds to ADP-actin

fimbrin and alpha-actinin

Examples of actin bundling proteins???

fimbrin

Actin bundling protein which tightly packs actin to prevent myosin II from entering

alpha-actinin

Actin bundling protein which loosely packs actin to allow mysin II to enter bundle

binds to Arp 2/3 complex

How to bacterial parasite use membrane protein ActA to

Myosins

What are the actin-based motor proteins?

Myosin II

What myosin is in skeletal muscle?

two heavy chains, coiled coil, four light chains

What is the structure of myosin II like?

done

Take a moment to study how myosin II walks along actin microfilaments…

gain ATP

What causes myosin II head to detach from actin?

Hydrolysis of ATP to ADP

What causes the cocking of the myosin II head?

after phosphate from ADP leaves

When does the myosin II head bind to actin?

letting got of ADP

What cause the power stroke of the myosin II head?

z-disc

What are the ends of a sarcomere called?

actin

what filament is attached to the z-discs of a sarcomere?

tropomyosin and tropinin

What proteins regulate skeletal muscle contraction?

Tropomyosin

What protein binds the actin filament groove to cover the myosin binding site?

to tropomyosin

Where is troponin bound?

when calcium binds to troponin

What causes tropomyosin to be pulled away from actin?

calcium

What binds to troponin to cause it to pull tropomyosin away from actin?

non-skeletal muscle myosin II is activated by MLCK by phosphorylation

What is the major difference between skeletal muscle myosin II and non-skeletal muscle myosin II?

MLCK, myosin light chain kinase

What is the enzyme activates non-skeletal muscle myosin II by phosphorylation?

radiating outward from nucleus

Where are microtubules located in the cell?

Microtubules

What filament makes up cilia and flagella in Eukaryotes?

heterodimer

What oligomeric state is the subunit of microtubules?

beta-tubulin and alpha-tubulin

What are the two subunits of the heterodimer of microtubules?

GTP

What is alpha-tubulin bound to?

GTP or GDP

What is beta-tubulin bound to?

beta-tubulin

Which microtubule heterdimer sub-unit can hydrolyze GTP to GDP?

13 protofilaments with lumen inside

What is the cross section of a microtubules like?

dynamic instability

What is it it called when the plus end grows and shrinks in quick succession?

when the concentration of free tubulin is between the critical concentration of GTP and GDP bound at the plus end

When does dynamic instability occur in microtubules?

Rigid structure

What is the structure of microtubules like when beta-tubulin is bound to GTP?

gamma-TuRC

What protein cause microtubule nucleation?

14 gamma-TuSC subunits

What are the components of gamma-TuRC? (microtubules)

Fourteen

How many gamma-TuSC subunits are in a gamma-TuRC to nucleate microtubules?

13 microtubule protofilaments

What attatches to 14 gamma-TuSC?

the minus end

Which end of microtubules does gamma-TuRC nucleate?

MTOC, Microtubule-Organizing Center, pericentriolar material

What is the origin point of microtubules (example: Centrosome)? From where do microtubules grow specifically out of?

7 copies of gamma-TuSC in spiral

What do we need to make a microtubule nucleus?

pericentriolar material as part of the centrosome

From where do microtubules originate in animal cells?

minus end

What side of microtubules are stuck into the pericentriolar material?

microtubules

What filament helps position the centrosome in the middle and also positions other organelles?

centrioles

What structure is embedded into the centrosome?

microtubules

What filament makes up the centrioles?

microtubules triplet with 9-fold circular symmetry

Describe the structure of the microtubules in the centrioles?

one centriole normally, two centrioles before division

How many centrioles does a cell have?

Microtubule associated proteins

What are MAPS?

MAP2 and tau

What is the MAPS for spacing microtubules apart?

MAP2

Which MAP spaces microtubules apart a far distance?

tau

What MAP spaces microtubules apart a short distance?

Kinesin-13 and XMAP215

Which MAPS affect the rate of microtubule polymerization at the plus end?

XMAP215

Which MAP enhances microtubule growth through stabilization?

kinesin-13

Which MAP promotes microtubule catastrophe through destabilization?

katanin

Which MAP chops up microtubules?

stathmin

Which MAP sequesters tubulin dimers, so they cannot be added to a microtubule filament?

kinesins and dyneins

What are microtubules based motor proteins called?

towards the plus end

Which way do kinesins walk along microtubules?

done

Take a moment to study how kinesins walk along microtubules…

when bound to ATP

When are kinesins bound TIGHT to microtubules?

after ATP to ADP hydrolysis

When are kinesins bound LOOSE to microtubules?

beta-tubulin

To what microtubule sub-unit do kinesins bind?

dyneins

What is the microtubule based motor protein which walks towards the minus end?

towards the minus end

Towards what end does dynein walk along microtubules?

dynactin complex

What is the intermediate handle between the dynein and vesicle?

disperses melanin vesicles on kinesins towards plus end of microtubules

What does increasing cAMP do to melanin vesicles?

aggerates melanin vesicles on dynein towards minus end of microtubules

What does decreasing cAMP do to melanin vesicles?

towards plus end, periphery, anterograde

Which way do kinesins walk on microtubules?

towards minus end, center, retrograde

Which way do dynein walk on microtubules?

sperm cell

What is the only cell were flagella is found in animals?

moving fluids

What do fixed cells use cilia for?

microtubules

What filament makes up flagella and cilia in eukaryotes?

movement of fluid

What are cilia used for in lungs?

cell movement

what are flagella used for in sperm?