Chp4. Cytoskeleton

Question 1

What are the three proteins found in the cytoskeleton that Dr. Rice wants us to know

Answer 1

1. actin
2. intermediate filaments
3. microtubules

Question 2

What are the 3 functions of actin in the cytoskeleton

Answer 2

1. consistency of cytosol
2. cell movement
3. cell division

Question 3

what are 2 functions of actin in the nucleus

Answer 3

1. structure

2. gene transcription

Question 4

What is G actin

Answer 4

globular actin - single subunit

Question 5

what is F actin

Answer 5

filimentous actin two strands of polymerized G actins wound together

Question 6

Is F actin polymerization energy dependent

Answer 6

very much - ATP

Question 7

What end are G actins added to

Answer 7

G+ end

Question 8

describe each step of actin formation

1. lag
2. polymerization
3. steady state

Answer 8

1. 3 G actins join together to make nucleation site
2. G actins are added to the + end of the nucleation site
3. G actin monomers are added at the same rate they are removed

Question 9

What is the major role of F actin

Answer 9

regulate state of cytosol sol/gel

Question 10

What is profilin what does it do

Answer 10

actin regulating protein, binds g actin monomers to prevent polymerization

Question 11

What is cofilin what does it fo

Answer 11

actin regulating protein, breaks F actin into smaller segments by twisting action

Question 12

Gelsolin

Answer 12

fragments F actin - requires Ca+ to do it

Question 13

What does dystrophin do (2)

what happens if there is a genetic defect

Answer 13

1. links actin to basement membrane -
2. gives muscle its tensile strength
3. muscular dystrophy

Question 14

What is the function of intermediate filaments

Answer 14

structure support

Question 15

Does the process of creating I.F.’s require energy

Answer 15

no

Question 16

What is the roll of microtubules in the cytosol (2)

Answer 16

1. intracellular transport/highway

2. movement of chromosomes during division

Question 17

What type of energy does microtubule formation require

Answer 17

GTP

Question 18

What is a protofilament

Answer 18

linear chain of heterodimers

Question 19

What is important about the GTP cap on microtubules

Answer 19

where new dimers are added - holds the molecule together without it it peels like a banana

Question 20

what happens when dimer addition to microtubules slows

Answer 20

they become disassembled

Question 21

Three functions of microtubules

Answer 21

1. chromosomal movement
2. cillia and flagella
3. intracellular

Question 22

what cytoskeleton component organizes the mitotic spindles in mitosis

Answer 22

microtubules

Question 23

what cytoskeleton element is important for vesicle and organelle movement

Answer 23

microtubules

Question 24

What does contraction of actin in non muscles cells do

Answer 24

1. contraction provides support
2. Necessary for cell movement
3. Necessary for division