Exam 3

Question 1

The cytoskeleton is a network of protein _____ extending throughout the _______ in all ________ cells

Answer 1

Filaments,
Cytoplasm,
Eukaryotic

Question 2

Note the two functions of the cytoskeleton:

Answer 2

1. Structural framework (scaffold for shape and cytoplasmic organization)
2. Movement (for entire cell movement and transport of organelles/other structures thru cytoplasm)

Question 3

Mostly ______ filaments around the edges of the membrane, mostly ______ connecting to the nucleus radially outward to outer edges, Mostly _______ in between throughout cytoplasm in between

Answer 3

Actin,
Microtubules,
Intermediate filaments

Question 4

Name the three principal elements/components that make up the cytoskeleton, which are held together and linked to subcellular organelles and plasma membrane by _______

Answer 4

1. Actin filaments (8nm)
2. Intermediate filaments (10nm)
3. Microtubules (25nm)

Accessory proteins

Question 5

Which principal cytoskeleton element is not involved in cell movement (directly)?

Answer 5

Intermediate filaments

Question 6

Main function of the intermediate filaments is…

Answer 6

They enable cells to withstand the mechanical stress that occurs when cells are stretched

Question 7

There are _____ classes of IF’s. _____ in cytoplasm and _____ in the nucleus.

Answer 7

4 classes,
3,
1,

Question 8

The 3 types of cytoplasmic IF’s and what cells they are found in?

Answer 8

1. Keratin filaments (in epithelial cells)
2. Vimentin & Vimentin-related filaments (in connective tissue cells, muscle cells, glial cells)

Question 9

The one class of nuclear IF?

Answer 9

Nuclear Lamins (in all animal cells)

Question 10

Appearance of IF’s in cell:
IF’s form a network throughout the cytoplasm, surrounding the _____ and extending out to the cell periphery, where they are anchored to the ______. They are also indirectly connected to neighboring cells through a cellular structure called the _____.

Answer 10

nucleus,
plasma membrane
desmosome

Question 11

Describe the assembly of mature IF’s:
Two _____ ______ wrapped using their central alpha-helical domains to form a _____-______ _____. The two dimers associate in a ______ and ______ fashion to form a tetramer. This thus constitutes a mature IF, in that it does NOT have ______ (one end resembles the other). The NH2 ends will extend out more than the COO- ends.

Answer 11

parallel monomers,
coiled-coil dimer,
staggered and antiparallel,
polarity

Question 12

Maturation of cytoplasmic IFs results in a ___-____ _____,
_____ ________ then laterally associate and are added to the growing IF. Unlike microfilaments and microtubules, there is no______ ______ and IFs build onto _____ IFs. Thus, the IF network is not very _______.

Answer 12

rope-like structure,
Eight tetramers,
nucleation involved,
preexisting,
dynamic

Question 13

Two functions of the nuclear lamina:

Answer 13

An IF composed fibrous network that:
1. supports the nuclear membrane
2. provides attachment sites for the chromatin

Question 14

Intermediate filaments underlying the inner face of the nuclear envelope form the ______ _______

Answer 14

Nuclear lamina

Question 15

How does the the nuclear lamina differ from the cytoplasmic IFs?

Answer 15

in structure since it forms a meshwork as opposed to a rope-like structure.

Question 16

The nuclear lamina _____ _____ ______ ______ when the nuclear envelope breaks down. This is regulated by ______ of the lamina to cause disassembly, and _______ to allow for its reformation.

Answer 16

disassembles with each cell division,
phosphorylation,
dephosphorylation

Question 17

Mutations in nuclear lamin protein are associated with _______ (premature aging in children)

Answer 17

Progeria

Question 18

Three main functions of microtubules:

Answer 18

1. the separation of chromosomes during mitosis
2. the intracellular transport of membrane-bound vesicles and organelles
3. cell movement

Question 19

Microtubules are _____, ______ ______ approximately 25 nm in diameter. They are _______ structures that continually undergo ______/_______.

Answer 19

Rigid, hollow rods
Dynamic
Assembly / disassembly

Question 20

MT’s are composed of a single type of globular protein, called _______, which is a _______ consisting of 2 closely related proteins: 1._______ and 2.________

Answer 20

Tubulin,
Heterodimer,
1. alpha-tubulin
2. beta-tubulin

Question 21

Dimers of ______ & _______ tubulin (via ________) form a ___________.

Answer 21

Alpha & beta tubulin,
Non-covalent bonding,
Protofilament,

Question 22

The alpha-tubulin is to _______, and beta-tubulin is for _______. The _______ is considered the growing end (determines direction of movement along MT’s)

Answer 22

minus-end,
plus-end,
plus-end.