lecture 12 and 13/14

Question 1

Troponin is a ____ binding protein that regulates muscle contraction

Answer 1

Ca2++

Question 2

Rho, Rac and Ras (like Rab and Ran) are:

Answer 2

GTPase proteins that influence actin assembly

Question 3

In many eukaryotic cells, actin can typically be found in what main location

Answer 3

Cell cortex

Question 4

Filament Dynamics of microtubules and actin filaments are regulated by similar activities

Answer 4

Nucleotide binding and hydrolysis on growing end of the filament b) Proteins acting to influence filaments or monomers

Question 5

Actin filaments are composed of actin monomers and grow much like microtubules, except ___ is carried by monomers

Answer 5

ATP

Question 6

In cells the concentration of actin is _____, with about half of it being held in monomers through the action of sequestering proteins

Answer 6

very high

Question 7

The system equilibrium in the cell is poised for very ____ polymerization

Answer 7

rapid

Question 8

Filament nucleation occurs by ____ ____or formin activity which is locally stimulated/regulated

Answer 8

Arp complex

Question 9

Filaments are constantly being remodeled by ______ severing and further addition and branching.

Answer 9

(gelsolin)

Question 10

Much more actin in cells than needed, so the problem is not availability, but how to keep it out of filaments the solution _____ is sequestering (thymosin and profilin) and _____ capping.

Answer 10

monomer filament

Question 11

: Crawling of cells over surfaces is an actin-dependent process what anchors the cell

Answer 11

the cortex

Question 12

: Crawling of cells over surfaces is an actin-dependent process what pulls the cell

Answer 12

myosin II contraction at the back end of the cell

Question 13

: Crawling of cells over surfaces is an actin-dependent process what pushes the cell

Answer 13

the focal contracts that contain intergrin

Question 14

when the cells Push - are ______&_________ are extended from the cell body; integrins help provide “traction” by adhesion to substrates

Answer 14

Lamellipodia and filopodia

Question 15

Actin filament nucleation that produces a branch from existing filaments is controlled directly by:

Answer 15

ARP 2/3 complex

Question 16

How do ARP complex nucleate new filaments

Answer 16

Side binding and generation of a “Y” shaped branched network

Question 17

Nucleation of new filaments near the leading edge of cell movement by

Answer 17

ARP complex

Question 18

Nucleation of new filaments in filopodial extensions occurs by activities of formins, adding to the ________ of the filament and pushing the membrane “spike”_____

Answer 18

plus end outward

Question 19

___ GTPase polarity and signaling proteins that control regulators of the ___ cytoskeleton

Answer 19

Rho actin

Question 20

For proteins regulated by GTP/GDP binding, it is the case that:

Answer 20

GTP is bound to the protein and converted to GDP + Pi as it acts on another protein
The protein with GDP bound releases GDP and then binds a new molecule of GTP to do another cycle of regulation

Question 21

Signaling starts on the exterior of the cell through_____ these help set up _____contacts which are locations of actin filament assembly and signal transduction

Answer 21

integrins focal

Question 22

Myosin I is involved in

Answer 22

vesicle and membrane movement

Question 23

Myosin II

Answer 23

sliding/contraction in muscles, cytokinesis contractile ring,
trailing end of migrating cells

Question 24

Myosins move via

Answer 24

ATP hydrolysis

Question 25

Muscle contraction involves rapid and dynamic control of contacts between ______ filaments and actin filaments in ordered structures called _____

Answer 25

myosin sarcomeres

Question 26

Thick filaments (myosin filaments) 
Thin filaments are...

Answer 26

(actin filaments anchored to Z discs

Question 27

Thick filaments (myosin filaments) 
Thin filaments are...

Answer 27

(actin filaments anchored to Z discs

Question 28

Structure of a sarcomere -

___ is consumed by each head as it moves along the actin filament

Answer 28

ATP, myosin

Question 29

What is/are the signal(s) that allows muscle contraction

Answer 29

Ca++ binding to troponin

Question 30

motor neuron->______->t-tuble->_________->sarcoplasmic reticulum->__________

Answer 30

signal, action potential, calcium release

Question 31

Ca++->________->_________

Answer 31

troponin tropomyosin

Question 32

Cytokinesis: another contractile function of

____and ______ filaments

Answer 32

actin myosin-II

Question 33

Kinetochores are microtubule interacting

protein complexes built at ___________________

Answer 33

centromeres in chromosomes

Question 34

The distance between the poles of the mitotic spindle _____ during progression through anaphase

Answer 34

changes

Question 35

At metaphase of mitosis when all replicated chromosomes are at the metaphase plate:

Answer 35

The chromosomes are under tension from the poles of the spindle via kinetochore microtubules

Question 36

A specialized protein structure that assembles at the centromeres of chromosomes and binds spindle microtubules during cell division

Answer 36

kinetochores

Question 37

Cytokinesis of cells occurs by the interaction of ____ ______ with actin to contract and divide the plasma membrane

Answer 37

myosin II proteins