The Cytoskeleton I- Structure

Question 1

What is the significance of the cytoskeleton?

Answer 1

represents bones of the cell
important in organization fo the cell
maintains correctly shaped cells
insures cells are properly structured internally

Question 2

What are functions of the cytoskeleton?

Answer 2

moves the cell
rearranges the cellular compartment
supports the plasma membrane
mechanical strength
pulls chromosomes apart during cell division
guides intracellular traffic
vesicles move using cytoskeleton as sidewalk
motor (for sperm) and crawling (WBC, fibroblasts)
muscle cell contraction

Question 3

What happens if the cytoskeleton has defects?

Answer 3

disease can develop

Question 4

What is RBC cytoskeleton is defective?

Answer 4

leads to anemia which can be severe and lethal

Question 5

What disease can anemia lead to?

Answer 5

heredity spherocytosis

Question 6

What is heredity spherocytosis?

Answer 6

RBS spherical not biconcave
fragile red blood cells burst
hemolytic anemia
cytoskeleton protein defects or deficiencies can lead to serious disease

Question 7

Cytoskeleton filaments are consisted of multiple ______

Answer 7

protofilaments

Question 8

What are protofilaments?

Answer 8

long linear strings of protein subunits joined end to end

Question 9

Are protofilaments thermally unstable?

Answer 9

yes, easy to break one linear filament

Question 10

When cytoskeleton filaments are created from multiple protofilaments bound side to side they _______ breakage by ______ ________ conditions

Answer 10

resist; ambient thermal

Question 11

What are the three main types of filaments?

Answer 11

actin filaments
microtubules
intermediate filaments

Question 12

What are actin filaments?

Answer 12

two stranded helical polymers of the protein actin
actin subunits are compact and globular
flexible structures 5-9 in diameter

Question 13

What is the role of actin filaments?

Answer 13

determine the shape of cell’s surface and are necessary for whole cell locomotion, secretion, endocytosis

Question 14

What are the properties of microtubules?

Answer 14

forms tube like structure
determine the positions of membrane enclosed organelles
directs intracellular transport

Question 15

What do microtubules make up?

Answer 15

centrioles and mitotic spindles

cilia and flagella

Question 16

What contributes to cystic fibrosis?

Answer 16

lack of function in cilia

Question 17

Describe the structure of microtubules

Answer 17

long hollow cylinders
made of tubulin subunits
long and strait 
more rigid than actin 
have centrosomes

Question 18

What are properties of intermediate filaments?

Answer 18

provide mechanical strength
strong filament
resists mechanical stress
allows formation of hair and fingernails

Question 19

Describe the structure of intermediate filaments

Answer 19

rope like fibers, 10 nm diamter
large heterogenous family
made of smaller subunits that are elongated and fibrous
span from one cell-cell junction to another

Question 20

Why are intermediate filaments in a staggered organization?

Answer 20

tolerates bending and stretching

forms rope like structure

Question 21

What does the apical surface do?

Answer 21

absorbs nutrients

Question 22

Are microvilli on the apical or basolateral surface?

Answer 22

apical

Question 23

What happens at the basolateral surface?

Answer 23

cells transfer nutrients to bloodstream

Question 24

How is polarity maintained for intestinal cells?

Answer 24

maintained by actin filaments, microtubules, and intermediate filaments

Question 25

What forms stable cell surface protrusions?

Answer 25

actin

Question 26

What type of filament is attached to desmosomes and hemidesmosomes?

Answer 26

intermediate filaments

Question 27

What filament forms tracks to get newly synthesized proteins to proper locations?

Answer 27

microtubules

Question 28

What builds a cytoskeleton filament?

Answer 28

protein subunit

Question 29

Cytoskeleton filaments (or polymers) are held together by weak ________

Answer 29

noncovalent interactions

Question 30

Assembly and disassembly of the cytoskeleton occurs_____

Answer 30

rapidly

Question 31

____ subunits are used for assembly fo actin filaments

Answer 31

actin

Question 32

What shape does actin subunits form?

Answer 32

helical

Question 33

Actin monomers contains binding site for _____ or _____

Answer 33

ATP or ADP

Question 34

Actin filaments are arranged ______ to generate structural polarity

Answer 34

head to tail

Question 35

What are the two ends of an actin filament?

Answer 35

plus and minus end

Question 36

What is the plus end of an actin filament?

Answer 36

fast growing or fast shrinking end

Question 37

What is the minus end of an actin filament?

Answer 37

slow growing or slow shrinking end

Question 38

ATP actin _______ and ADP actin ______

Answer 38

polymerizes (grows); disassembles (shrinks)

Question 39

What subunits form microtubules?

Answer 39

tubulin subunits

Question 40

Describe tubulin

Answer 40

hetero dimer of alpha tubulin and beta tubulin with non covalent bonds both have binding site for one GTP

Question 41

The top beta tubulin binds to bottom _____ subunit

Answer 41

alpha

Question 42

Do microtubules have plus and minus ends?

Answer 42

yes

Question 43

What is polymerization?

Answer 43

assembly of actin or tubulin subunits into a linear polymer

Question 44

What is depolymerization?

Answer 44

removal of monomers at the ends of the polymer

Question 45

What are the steps in formation of cytoskeletal filaments?

Answer 45

1. filament nucleation 2. filament elongation- growth phase 3. steady state- equilibrium phase

Question 46

What is filament nucleation?

Answer 46

process of rotation of initial aggregate, or nucleus

Question 47

What is filament elongation?

Answer 47

subunits are quickly added onto the ends of nucleated filaments

Question 48

What is the steady state?

Answer 48

rate of monomer addition equals the rate of monomer loss

Question 49

What are actin and tubulin?

Answer 49

enzymes that catalyze ATP or GTP

Question 50

What is the T form of subunit?

Answer 50

ATP/ GTP

Question 51

What is the D form of subunit?

Answer 51

ADP/GDP

Question 52

What formation does the plus end remain in?

Answer 52

T formation

Question 53

What formation does the minus end remain in?

Answer 53

D formation

Question 54

What is tread milling?

Answer 54

plus end growing while minus end is shrinking

Question 55

Where does tread milling predominate?

Answer 55

actin filaments

Question 56

What is catastrophe?

Answer 56

change from growth to rapid shrinkage

Question 57

What is rescue?

Answer 57

change from rapid shrinkage to growth

Question 58

Adding tubulin GTP produces ______ protofilaments

Answer 58

straight

Question 59

Where does dynamic instability predominates?

Answer 59

microtubules

Question 60

Is there a nucleotide binding site on intermediate filaments?

Answer 60

no

Question 61

What are keratins?

Answer 61

the most diverse group of intermediate filaments

Question 62

How many keratins are found in human epithelial cells?

Answer 62

20

Question 63

How many keratins are specific to hair and nails?

Answer 63

10

Question 64

How many distinct keratin goes are in the human genome?

Answer 64

50

Question 65

True or false? Actin monomers are microtuble subunits?

Answer 65

False