Chapter 14

Question 1

The cytoskeleton is composed of three main types of protein filaments:

Answer 1

Actin filaments
Microtubules
Intermediate filaments

Question 2

regulate assembly and disassembly of actin filaments, cross-linking into bundles and networks, and associations with other cell structures.

Answer 2

Actin-binding proteins

Question 3

the first step of actin polymerization

Answer 3

Nucleation

Question 4

bind ATP-actin and nucleate initial polymerization of long unbranched actin filaments.

Answer 4

Formins

Question 5

binds actin monomers and stimulates exchange of bound ADP for ATP, increasing the local concentration of ATP-actin.

Answer 5

Profilin

Question 6

initiate growth of branched actin filaments, important in driving cell movement at the plasma membrane.

Answer 6

Arp2/3 complex

Question 7

stabilize actin filaments by binding lengthwise along the groove of the filament.

Answer 7

Tropomyosins

Question 8

severs filaments, generating new ends which are then available for polymerization or depolymerization.

Answer 8

Cofilin

Question 9

Cell-cell contact is mediated by transmembrane proteins called

Answer 9

cadherins

Question 10

Actin filaments are cross-linked by (2 things)

Answer 10

fimbrin and villin.

Question 11

a molecular motor— converts chemical energy (ATP) to mechanical energy, generating force and movement.

Answer 11

myosin

Question 12

Each myofibril is a chain of contractile units called

Answer 12

sarcomeres

Question 13

The actin and myosin filaments slide past one another so that the actin filaments move into the A band and H zone.

Answer 13

sliding filament model

Question 14

the type of myosin in muscle

Answer 14

myosin II

Question 15

In nonmuscle cells and smooth muscle, contraction is regulated primarily by _________ of a myosin light chain.

Answer 15

phosphorylation

Question 16

Have globular head groups that act as molecular motors.

Answer 16

myosin I

Question 17

Two-headed dimer that transports vesicles and other cargo along actin filaments.

Answer 17

myosin V

Question 18

rigid hollow rods.

Answer 18

microtubules

Question 19

diameters intermediate between actin filaments and microtubules.

Answer 19

Intermediate filaments

Question 20

the major intermediate filaments of many neurons; provide support for long axons.

Answer 20

NF proteins