week 5 Flashcards
1
Q
how are cells held together?
A
- you need intracellular and extracellular adhesion
- proteins inside and outside will hold things in place
- ## cell-cell adhesion proteins
2
Q
what moves in the cell?
A
- organelles, cells and tissues
3
Q
how do tings move in cells and how do cells move
A
cytoskeletal proteins
4
Q
cytoskeleton
A
- intricate network of protein filaments that extend throughout the cytoplasm
5
Q
what makes up the cytoskeleton?
A
- microfilaments
- microtubles
- intermediate filaments
6
Q
microfilaments
A
- 7-9 nm width
- actin subunits
- this is the thinnest component
7
Q
mictotubules
A
- alphabeta- tubulin dimer subunits
- this is the thickest component
- 25 nm width
8
Q
intermediate filaments
A
- various subunits
- 10 nm width
9
Q
how can the cytoskeleton be visualized
A
- through immunofluorescence
10
Q
DNA length. of one turn?
A
- 10 nm = 100 A
11
Q
is there any empty space in a cell
A
NO- solvents like cytoplasm or RBC floating blood stream
12
Q
microtubules
A
- polymer of alpha and beta tubulin
- 25 nm in diameter
- can be up to 100s of micrometers long
- organize the
13
Q
alpha and beta tubulin
A
- monomer of microtubules
- 55 kDa each
- alpha-beta dimer
- have polarity
14
Q
why does the alpha beta dimer have polarity
A
- polyervizes faster on the positive side
- the positive is the beta tubulin end
- the negative is the alpha tbulin end
15
Q
how long is one dimer of alpha beta tublin
A
8 nm
16
Q
how is a seam created in microtubule protofilaments
A
- not folding properly, all the subunits ar not lined up
17
Q
protofilaments
A
- dimers of the Dublin subunits strung together
- long strands
18
Q
how many protofilaments ar included in the hollow tubes of mictobtules
A
13
19
Q
what are the largest cytoskeletal filaments that we discuess
A
microtubules
20
Q
in what form do the subunits have to be in, in order to polyermize
A
in GTP form
- the order of polymerization is alpha beta alpha beta
21
Q
dimeric tubulin subunit
A
- 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
22
Q
how can MT protofilaments be arranged
A
- singlet
- doublet
- triplet
23
Q
singlet
A
- found in cytoplasm
- 13 protofilmanets form a single tube of 25 nm.
- 13 protofilaments
24
Q
doublet
A
- made up of two microtubules
- 13 A protofilaments and 10 B protofilaments subunits
- in cilia nd flagella
25
mictorbuulse in cytoplasm
- the cytoplasm of all cell have these
- e.g. nerve axon
- singlet mmicrotbules
26
axonemela microtubules
- specific organization and type of microtbubule found in cilia and flagella
- doublet microtubules
27
what do singlet mictobrubles in cytoplasm and nerve axons fo
transport things along axons to nerve cell boies
28
MTOC
- main one = centrosome
- where microsomes polyermize from
29
centrosome
- contains centrioles
- centrioles are not found in plantscen
30
centriole
- 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
31
mother and daughter centrioles
- centrioles must replicate during mitosis
32
pericentriolar matrix
has proteins like gamma tubulin, augmen, \- surrounds the centrioles
33
augment and gamma tubulin
- found in the pericentrioar matrix
- form complexes that allow the singlet microtubules to polyermize
34
in what direction are singlet microtubules polyermized
- with plus end going away from the centrosome
- the e end is in the pericentrular matrix
35
How many triplets in a centriole ring?
9
36
gamma tubulin ring complex
- provides nucleating sites for mcirotiubules.
- facilitates microtbubuel branching with agumin
- gamma tubulin ring complex = nucleating site
37
where does polymerization start
- gamma tubulin and gamma tubulin ring complex, located at negative end
38
where do microtubule assembly and disassembly occur
at plus end
39
what does a nucleation site do
accelerates initial polyermization
40
nucleaiton
- micotunule can grow on already existing microtubules (these are used a a nucleus)
-
41
why is the - end never capped
- because ti is capped
- but plus end will grow and shrink
42
why is elongating/poymerizing from single subunits so time consuimg/
- must form nuclei
- adding nuclei already means no need for formation, means faster poylermization, if enough subunits to be above the critical concentration
43
actin example of closed system polyermization
- 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)
44
dynamic instability
oscillations in length
- cells need this in order to get to different locations
45
what does dynamic instability depend on
- the presence or absence of a GTP beta tubulin cap
46
microtubule disruption drugs
colchicine
taxol
anticancer drugs
47
colchicine
depolyermization of all teh singlet microtubules
48
taxol
stabilizes
