new mat. final exam

Question 1

largest component of cytoskeleton

Answer 1

microtubules

Question 2

a “true cytoskeleton is only present in what kind of cell?

Answer 2

Eukaryotic

Question 3

3 components of the cytoskeleton

Answer 3

Microtubules (MT)
Microfilaments (MF)
Intermediate filaments (IF)

Question 4

general functions of the cytoskeleton

Answer 4

Maintaining cell shape
Shifting cell contents
Moving cell

Question 5

a microtubule Monomer with combined alpha- and beta-tubuli is called?

Answer 5

heterodimers

Polymerize into large, hollow tube (25nm across)

Question 6

microtubules being dynamic means?

Answer 6

continually growing / shrinking

Question 7

microtubules having directionality means

Answer 7

they have a positive end and a negative end

Question 8

what Grows out of microtubule organizing center (MOC)

Answer 8

Centrosomes with centrioles

Question 9

The Centrosome is an area / location that

Answer 9

Located near nucleus in many cells
and Contains (2) centrioles

Question 10

centriole

Answer 10

a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division.

Question 11

centrioles are composed of and facilitate

Answer 11

Composed of (9) sets of triplet MTs at right angles to each other
Also contains γ-tubulin and associated proteins Provides nucleation sites (limited number!)
Facilitates assembly of MTs

Question 12

catastrophin

Answer 12

breaksdown microtubules

Question 13

In the cell, MT formation is

Answer 13

ordered, regulated

Question 14

Accessory proteins can

Answer 14

stabilize, destabilize MT
Microtubule associated proteins (MAPs) – stabilize
Some kinesins (ex: catastrophin) – destabilize

Question 15

Cells form sets of MTs in specific locations for

Answer 15

specific functions
-Assembly process is sped up during times of need (ex:
cell division)

Question 16

Functions of MTs:

Answer 16

Maintaining cell shape
    Resist pushing forces
Shifting cell contents
    Mitotic spindle 
    Metaphase plate 
    Organelle movement Tracks – intracellular vesicle/cargo
    Transport            
Moving cell
   Flagella Cilia

Question 17

Have “Dynamic Instability”

Answer 17

Either growing / shrinking can dominate (by needs of cell) So MTs are constantly changing; dynamic structures
“Treadmilling” Mg+2 and GTP required Treadmilling: Each heterodimer binds (2) GTP
α-tubulin-GTP β-tubulin-GTP

Question 18

GTP-tubulin binding to MTs promotes stable

association of more GTP-heterodimers means

Answer 18

GTP cap

Question 19

MT growth requires increased [tubulin]; creates increased [GTP-tubulin means..

Answer 19

GTP cap: High number of GTP-tubulin units associated

with each other Protects MT from loss of subunits from plus end

Question 20

What does GTP do?

Answer 20

GTP hydrolysis allows incoming tubulin to be bound to tubulin already in MT

Creates boundary mid-tubule

- GTP-tubulin cap near plus (+) end 
- GDP-tubulin near minus    (-) end

MT that is gaining GTP-tubulin at plus (+) end faster than losing GDP-tubulin at minus (-) end growing

Question 21

When [tubulin] is low

Answer 21

decreased [GTP-tubulin] depletes the cap

Question 22

Shrinking MTs have a reduced GTP-tubulin cap structure; have GDP-tubulin close to plus (+) end

Answer 22

Losing tubulin at plus end and minus end leads to shrinking

Question 23

what plays a role when MTs lose enough GTP-tubulin to trigger a collapse of entire MT

Answer 23

Catastrophin proteins

Question 24

structure of microfilaments

Answer 24

Composed of actin monomers
Individual molecules = G-actin (globular) Polymerized = F-actin (filamentous)
Two strands of actin wrap around each other

Question 25

Actin is classified into two broad groups

Answer 25

Muscle-specific (αactin)
Non-muscle-specific (βand γactin)
β-actin = named for basal side of cell γ-actin = named for apical side of cell

Question 26

Microfilaments have directionality

Answer 26

Minus = pointed end
Plus = barbed end

Question 27

functions of micro filaments

Answer 27

Maintaining Cell Shape
Shifting Cell Contents
Movement of Cell

Question 28

maintaining cells shape with microfilaments

Answer 28

• Structural support under plasma membrane (cell cortex)
• Ex: Spectrin and ankyrin in RBC
• Core of microvilli

Question 29

Shifting Cell Contents with microfilaments

Answer 29

• Cytoplasmic streaming

- Cleavage furrow in cytokinesis

Question 30

Movement of Cell with microfilaments

Answer 30

• Amoeboid movement (filopodia, lamellipodia)

- Muscle contraction

Question 31

microfilaments Share many features with MTs

Answer 31

Undergoes treadmilling
MF cap forms under increased [ATP-actin]
Has many associated proteins (promote assembly/disassembly)

Question 32

microfilament and microtubule associated proteins (promote assembly/disassembly)

Answer 32

Cap proteins 
Crosslink proteins 
Severing proteins 
Bundling proteins 
Branching/growth proteins

Question 33

intermediate filaments structure

Answer 33

Fall in between the MTs and MFs in size (8-12nm) Composed of different protein subunits
--Cell specific 
--Divided into 6 classes
Wound into cables to wound in filaments
Identical ends = no directionality
--Most stable cytoskeletal component 
--Least soluble

Question 34

assembly of intermediate filaments

Answer 34

individual protein strands
dimerize

o Dimers Tetramers
   Laterally staggered
   C- and N-terminals alternate
Creates protofilaments
    Tetramers lined up end-to-end
Protofilaments assemble into IFs

Question 35

intermediate filament functions

Answer 35

Form flexible cell skeletons
Shape cells (resist pulling forces)
Hold nucleus, certain organelles in place

Question 36

MTs resist

Answer 36

bending when cell is compressed

Question 37

MFs - contractile

Answer 37

elements; generate tension

Question 38

IFs - elastic

Answer 38

can withstand tensile forces