week 5

Question 1

how are cells held together?

Answer 1

• you need intracellular and extracellular adhesion
• proteins inside and outside will hold things in place
• ## cell-cell adhesion proteins

Question 2

what moves in the cell?

Answer 2

• organelles, cells and tissues

Question 3

how do tings move in cells and how do cells move

Answer 3

cytoskeletal proteins

Question 4

cytoskeleton

Answer 4

• intricate network of protein filaments that extend throughout the cytoplasm

Question 5

what makes up the cytoskeleton?

Answer 5

• microfilaments
• microtubles
• intermediate filaments

Question 6

microfilaments

Answer 6

• 7-9 nm width
• actin subunits
• this is the thinnest component

Question 7

mictotubules

Answer 7

• alphabeta- tubulin dimer subunits
• this is the thickest component
• 25 nm width

Question 8

intermediate filaments

Answer 8

• various subunits
• 10 nm width

Question 9

how can the cytoskeleton be visualized

Answer 9

• through immunofluorescence

Question 10

DNA length. of one turn?

Answer 10

• 10 nm = 100 A

Question 11

is there any empty space in a cell

Answer 11

NO- solvents like cytoplasm or RBC floating blood stream

Question 12

microtubules

Answer 12

• polymer of alpha and beta tubulin
• 25 nm in diameter
• can be up to 100s of micrometers long
• organize the

Question 13

alpha and beta tubulin

Answer 13

• monomer of microtubules
• 55 kDa each
• alpha-beta dimer
• have polarity

Question 14

why does the alpha beta dimer have polarity

Answer 14

• polyervizes faster on the positive side
• the positive is the beta tubulin end
• the negative is the alpha tbulin end

Question 15

how long is one dimer of alpha beta tublin

Answer 15

8 nm

Question 16

how is a seam created in microtubule protofilaments

Answer 16

• not folding properly, all the subunits ar not lined up

Question 17

protofilaments

Answer 17

• dimers of the Dublin subunits strung together
• long strands

Question 18

how many protofilaments ar included in the hollow tubes of mictobtules

Answer 18

13

Question 19

what are the largest cytoskeletal filaments that we discuess

Answer 19

microtubules

Question 20

in what form do the subunits have to be in, in order to polyermize

Answer 20

in GTP form
- the order of polymerization is alpha beta alpha beta

Question 21

dimeric tubulin subunit

Answer 21

• very stable (dimer is not easily separated)
• alpha tunulin binds gTP only
• beta tubulin can hydrolyze GTP (can be bound to either)
• beta gTP is hydrolyzed as the protofilament polymer grows

Question 22

how can MT protofilaments be arranged

Answer 22

• singlet
• doublet
• triplet

Question 23

singlet

Answer 23

• found in cytoplasm
• 13 protofilmanets form a single tube of 25 nm.
• 13 protofilaments

Question 24

doublet

Answer 24

• made up of two microtubules
• 13 A protofilaments and 10 B protofilaments subunits
• in cilia nd flagella

Question 25

mictorbuulse in cytoplasm

Answer 25

• the cytoplasm of all cell have these
• e.g. nerve axon
• singlet mmicrotbules

Question 26

axonemela microtubules

Answer 26

• specific organization and type of microtbubule found in cilia and flagella
• doublet microtubules

Question 27

what do singlet mictobrubles in cytoplasm and nerve axons fo

Answer 27

transport things along axons to nerve cell boies

Question 28

MTOC

Answer 28

• main one = centrosome
• where microsomes polyermize from

Question 29

centrosome

Answer 29

• contains centrioles
• centrioles are not found in plantscen

Question 30

centriole

Answer 30

• triplet microtubules
• two triplets that are ninety degrees to erah other
• striplets = pretty stable, and dont really polyermzie or depolyermize, which makes centrioles stable.
• has pericentriolar matrix

Question 31

mother and daughter centrioles

Answer 31

• centrioles must replicate during mitosis

Question 32

pericentriolar matrix

Answer 32

has proteins like gamma tubulin, augmen, - surrounds the centrioles

Question 33

augment and gamma tubulin

Answer 33

• found in the pericentrioar matrix
• form complexes that allow the singlet microtubules to polyermize

Question 34

in what direction are singlet microtubules polyermized

Answer 34

• with plus end going away from the centrosome
• the e end is in the pericentrular matrix

Question 35

How many triplets in a centriole ring?

Answer 35

9

Question 36

gamma tubulin ring complex

Answer 36

• provides nucleating sites for mcirotiubules.
• facilitates microtbubuel branching with agumin
• gamma tubulin ring complex = nucleating site

Question 37

where does polymerization start

Answer 37

• gamma tubulin and gamma tubulin ring complex, located at negative end

Question 38

where do microtubule assembly and disassembly occur

Answer 38

at plus end

Question 39

what does a nucleation site do

Answer 39

accelerates initial polyermization

Question 40

nucleaiton

Answer 40

• ## micotunule can grow on already existing microtubules (these are used a a nucleus)

Question 41

why is the - end never capped

Answer 41

• because ti is capped
• but plus end will grow and shrink

Question 42

why is elongating/poymerizing from single subunits so time consuimg/

Answer 42

• must form nuclei
• adding nuclei already means no need for formation, means faster poylermization, if enough subunits to be above the critical concentration

Question 43

actin example of closed system polyermization

Answer 43

• add actin monomers above citric concentration
• slow growth initially, because monomers must come together to form nuclei
• after that, can get rapid elongation.
• if u add nuclei from the start, no lag phase (.e.g having gamma tubullin ring complex which acts a. nucleus in the centrosome)

Question 44

dynamic instability

Answer 44

oscillations in length
- cells need this in order to get to different locations

Question 45

what does dynamic instability depend on

Answer 45

• the presence or absence of a GTP beta tubulin cap

Question 46

microtubule disruption drugs

Answer 46

colchicine
taxol
anticancer drugs

Question 47

colchicine

Answer 47

depolyermization of all teh singlet microtubules

Question 48

taxol

Answer 48

stabilizes