Bio 18 - Cytoskeleton Ii

Front 1

The actin subunit is __ (highly conserved amino acid sequence - __ identical between yeast and animal actin)

Back 1

Globular (G)-actin, 88%

Front 2

G-actin polymerizes into __, thin filaments (__)

Back 2

Filamentous (F)-actin, 6-7nm

Front 3

F-actin forms a __ (__ actin monomers per turn; __ per turn)
__ coiling around each other

Back 3

right-hand helix, 13, 37 nm, 2 parallel protofilaments

Front 4

Actin monomer is bound to __, which gets ___ to ___

Back 4

ATP, hydrolyzed, ADP

Front 5

The growing end will have ___ bound, similar to how the growing end of MTs have __ bound.

Back 5

ATP. GTP

Front 6

__ ends of __ mark the plus end and the __ end marks the minus end.

Back 6

Barbed, S1, pointed

Front 7

__ can be added to the minus end if the __ is high enough.

Back 7

Monomers, monomer concentration

Front 8

However, if the local concentration of monomer drops, the rate of dissociation from the minus becomes __

Back 8

faster than the rate of association.

Front 9

This equilibrium condition is called __ because the monomers are added to the plus end, move down the filament, and are released from the minus end.

Back 9

“treadmilling”

Front 10

Nucleators to know - __
__ nucleates__
__nucleate __

Back 10

Arp2/3 and formin, Arp2/3, branched networks, Formins, bundled, unbranched cables

Front 11

Spontaneous assembly of actin filaments from__ subunits is very slow and so __ are needed.

Back 11

G-actin, nucleators

Front 12

ARP2/3 “nucleates” actin filament assembly by ___

Back 12

providing a template or “seed” that can be elongated by subunit addition.

Front 13

Arp is an acronym for __

Back 13

actin-related protein

Front 14

Arp2/3 has function that is similar to __ with MTs.

Back 14

gamma-tubulin

Front 15

Unlike MTs, actin can form a __

Back 15

highly branched network.

Front 16

Arp2/3 can nucleate a new filament from the __ of an existing filament.

Back 16

sides

Front 17

Branched networks are found at the __ of __

Back 17

leading edge, migrating cells

Front 18

The cell can sense __ and move towards them in a process called __.

Back 18

molecules being released by the bacteria, chemotaxis

Front 19

__ binds to cell surface receptor, which activates ___, which activates __.

Back 19

Chemoattractant, WASP, ARP2/3

Front 20

Filaments not touching the membrane are __, those in contact with membrane __

Back 20

capped, push it outward

Front 21

Minus (__) ends on the back edge are disassembled with the help of ___.

Back 21

pointed, cofilin

Front 22

Whereas the Arp2/3 complex stayed at the ___, __ travels with the growing ___ end.

Back 22

minus end, formin, plus

Front 23

actin-rich cables can generate protruding spikes called __ (arrowheads), project from the large ___ at the end of this growing axon

Back 23

filapodia, lamellipodium

Front 24

Actin can generate movements by 2 mechanisms.
__ at the front of the cell pushes the membrane forward.
___ (actin structures) form and connect to an adhesion site at the front of the cell
__ driven contraction of the stress fibers pull the __

Back 24

Assembly, Stress fibers, Myosin Motor, back end forward.

Front 25

Type II myosin is also called __.

Back 25

"conventional myosin”

Front 26

Two monomers assemble into the dimeric __- held together by the __.

Back 26

myosin II, coiled-coil tails

Front 27

In the muscle, a bunch of myosin IIs assemble into a ___.

Back 27

thick filament with lots of heads

Front 28

__ because the heads on both sides of this filament will pull actin towards the __.

Back 28

Bipolar, center

Front 29

many muscle ___ fuse together during development to form this long cell.

Back 29

myoblasts

Front 30

Each muscle fiber is made up of a bundle of __.

Back 30

myofibrils

Front 31

Myofibrils consist of a repeating linear array of up to ___ contractile units called ___.

Back 31

100,000, sarcomeres

Front 32

A sarcomere extends from ___, and is made up of __

Back 32

Z-line to Z-line, actin, myosin and a few other associated proteins

Front 33

The minus ends of the actin filaments point towards __

Back 33

each other

Front 34

__ are descriptors given to these structures based on the electron micrograph images.

Back 34

The Z-line, I bands, A bands, H zones

Front 35

During contraction, the __ diminish in width as the fibers slide past each other

Back 35

I band and H zone

Front 36

__ has the best understood role in organelle transport.

Back 36

Myo V

Front 37

Cells that produce pigment for our skin and hair are called __.

Back 37

melanocytes

Front 38

Melanocytes __ and transport pigment granules to the __ ends of the processes.

Back 38

extend long processes, distal

Front 39

Pigment granules are also called __, filled up with the pigment __

Back 39

melanosomes, melanin

Front 40

Near the end of the process, the __ will hop over to an __ and use the __ to move into the very tip of the process.

Back 40

melanosome, actin filament, myosin Va motor

Front 41

__ is crosslinking an intermediate filament to 2 MTs in this image

Back 41

Plectin

Front 42

The only name to remember as an example of an IF is __.

Back 42

keratin

Front 43

__ major families of proteins; cell-type specific

Back 43

5

Front 44

Intermediate filaments are especially abundant in __

Back 44

tissue encountering mechanical stress (e.g. muscle, skin).

Front 45

There are more than __ different keratin proteins coded for by __ keratin genes.

Back 45

50, >50

Front 46

Unlike MTs, IFs

Back 46

do not have any polarity
do not possess any recognized organizing center in the cell.

Front 47

Blistering disorder resulting from an inherited mutation in a keratin gene (gene __)

Back 47

Epidermolysis bullosa simplex, 14

Front 48

__ is specifically required in the dividing cells at the base of the epidermis that attach to the underlying dermis.

Back 48

Keratin 14