BI203 Lecture 19: Cytoskeleton - Microtubule Motors, Movement, and Intermediate Filaments

Question 1

____ and ____: Molecular motors that move along microtubules powered by ATP hydrolysis.

Answer 1

kinesins, dyneins

Question 2

Most ____ move toward the plus end of microtubules = anterograde transport.

Answer 2

kinesins

Question 3

Most kinesins move toward the ____ end of microtubules = anterograde transport.

Answer 3

plus

Question 4

Most kinesins move toward the plus end of microtubules = ____ ____.

Answer 4

anterograde transport

Question 5

Most ____ move towards the minus end = retrograde transport.

Answer 5

dyneins

Question 6

Most dyneins move towards the ____ end = retrograde transport.

Answer 6

minus

Question 7

Most dyneins move towards the minus end = ____ ____.

Answer 7

retrograde transport

Question 8

A major role of microtubules is to transport ____, ____, and ____ through the cytoplasm.

Answer 8

macromolecules, vesicles, organelles

Question 9

Different members of the kinesin and dynein families are thought to transport cargo in ____ directions.

Answer 9

opposite

Question 10

____ ____ has two heavy chains and two light chains. The heavy chains have α-helical regions that form coiled-coils.

Answer 10

Kinesin 1

Question 11

____ ____ (11 nm) are an intermediate between actin filaments (7 nm) and microtubules (25 nm).

Answer 11

intermediate filaments

Question 12

Intermediate filaments play a structural role by providing ____ ____ as well as a ____ for intracellular signaling.

Answer 12

mechanical strength, scaffold

Question 13

Intermediate filaments are not directly involved in cell movements, but provide mechanical strength and a scaffold for the localization of ____ ____.

Answer 13

cell processes

Question 14

Intermediate filaments are ____ found in yeast, plants, and some insects.

Answer 14

NOT

Question 15

Intermediate filaments are composed of many types of proteins expressed in different types of cells.
Type I and II are ____, in epithelial cells.

Answer 15

keratins

Question 16

____, a type of intermediate filament, forms a network extending out from the nucleus toward the cell periphery.

Answer 16

Vimentin

Question 17

____, a type of intermediate filament, is expressed in muscle cells where it connects the Z discs of individual contractile elements.

Answer 17

Desmin

Question 18

____ (NF) ____ (with α-internexin) are the major intermediate filaments of many neurons; provide support for long axons.

Answer 18

neurofilament (NF) proteins

Question 19

Due to anti-parallel organization, intermediate filaments are ____ (have no electrical polarity).

Answer 19

apolar

Question 20

Most intermediate filaments can be ____ which regulates their assembly and disassembly (i.e. nuclear lamins).

Answer 20

phosphorylated

Question 21

Intermediate filaments have a central α-helical rod domain which plays a central role in filament assembly.
The head and tail domains determine the specific functions.
The central rod domains of two polypeptides form a coiled coil.
The dimers associate in a staggered antiparallel fashion to form tetramers, which assemble end-to-end to form protofilaments.
____ protofilaments wind together to form an intermediate filament.

Answer 21

8

Question 22

Intermediate filaments do NOT have distinct ends.

They are more stable and do ____ have the dynamic behavior of actin filaments or microtubules.

Answer 22

NOT

Question 23

Intermediate filaments form a cytoplasmic ____ in most cells, extending from a ring around the nucleus to the plasma membrane.
They can also associate with other cytoskeleton elements, providing a scaffold that organizes the internal structure of the cell.

Answer 23

network

Question 24

____ are molecular complexes of cell adhesion proteins and linking proteins that attach the cell surface adhesion proteins to intracellular ____ intermediate filaments.

Answer 24

desmosomes, keratin

Question 25

____ are similar to desmosomes in that they link the intermediate filaments to the extracellular matrix through plectin (a plakin) and integrins.

Answer 25

hemidesmosomes

Question 26

____ acts as a link between the three main components of the cytoskeleton: actin microfilaments, microtubules and intermediate filaments.

It plays an important role in maintaining the mechanical integrity and viscoelastic properties of tissues.

Answer 26

Plectin

Question 27

Some ____ link intermediate filaments to other elements of the cytoskeleton.
Plectin binds actin filaments and microtubules, forming bridges between them and between intermediate filaments.
This increases the mechanical stability of the cell.

Answer 27

plakins

Question 28

A study using transgenic mice with a certain mutation in an intermediate filament: ___, resulted in the mice having severe ____ abnormalities.

Answer 28

keratin, skin

Question 29

___ is caused by keratin gene mutations that interfere with normal assembly of keratin filaments.

Answer 29

EBS