week 3 thursday Flashcards
cytoskeleton
intricate network of protein fillaments:
microtubules
microfiliments
intermediate filliments
organize protein filaments of cytoskeleton in order of size (small to big)
microfiliments
intermediate filaments
microtubules
organize protein filaments of cytoskeleton in order of rigidity (least to most rigid)
microfiliments - flexible
intermediate fillaments - rigid
microtubules - neither, transports items in tubes
microfiliments
maintain cell shape, involved in muscle contractions and more
atp added to + end (has directionality, turns to adp (looses phosphate) the longer it is a part of the filament
intermediate filiments
made of coiled monomers that wrap around eachother, stacking these coiled monomers creates strong ropelike structure
provide tensile strength + IFs make up nuclear lamina
nuclear lamina
underlay of nuclear envelope that provides structure to nuclear envelope
tensile strength
how cells stay together and connected when under physical pressure (ex. being pulled apart)
microtubule structure
stacked alpha and beta heterodimers create a protofiliment, protofiliments combine to form the tube shape (microtubule)
centresome
made of microtubules. 9 groups of 3 microtubules make up larger tube (centriole) two of these purpendicuraly aligned make up the full centrosome
microtubules
have directionality due to alpha and beta alternation. all microtubules are synthesized in the centrosome.
vesicles travel through microtubules (movement driven by motor proteins)
kinesin
microtubule motor protein. + end directed (moves towards + end)
dynein
microtubule motor protein. - end directed (moves towards - end)
first phase of the cell cycle
- G1/G0
monitor internal + external environent, are there enough nutrients to grow and devide?
- if enough: G1 starts (cell growth, continued monitoring)
- not enough: G0 nothing happens
second phase of the cell cycle
- synthesis/S-phase
replicate chromosomes (DNA replication)
third phase of the cell cycle
- G2
monitor internal and external environments + cell growth (sort of like second G1)
fourth phase of the cell cycle
- mitosis
seperate chromosomes, nuclear devision, cytoplasmic devision (cytokenesis)
flow cytrometry
way of scientifically monotering the cell cycle
dye DNA in cells and run cells through laser cell-by-cell to read flourecense and create graph
cyclin-dependend kinases (Cdks)
tell/decide when/if cell moves to next phase of cell cycle
(catalytic subunit, phosphorilizes substances to trigger cell cycle events, can only phosphorilate when bonded w/cyclin)
cyclin
regulatory subunit, expression occilates (concentration of cyclin changes/is regulated)
what is cyclin concentration regulated by
transcription (slow increase) and proteolysis (fast decrease due to cell distruction)
what does phosphorilation to the cyclin-Cdk complex do
can either activate or inhibit, depends on which site is phosphorylated (inhibiting or activating site)
Cdk inhibitors (CKIs)
act as cell cycle brake.
blocks active site in cyclin-Cdk, causing inhibition
DNA damage checkpoints
block cell progression, places where cell stops + checks steps of the cell cycle
M-Cdk
active M-Cdk drives transition to mitosis/signals for mitosis to comence
regulates its own activity through positive feedback loop
how are mitotic spindles formed
M-Cdk reorganizes chromosomes by phosphorylating cohesion (which form sister chromatids)
mitotic spindles are assembled using microtubles, M-Cdk phosphorilates microtubule associated proteins (MAPs) and microtubule motor proteins (kenisin + dynein) to assemble spindles
prometaphase
M-Cdk phosphorilizes nuclear lamins (structure of nuclear envelope) which causes breakdown of the nuclear envelope
prometaphase/metaphase
connect chromosomes to mitotic spindle through keneticore
keneticore
massive protein complex at the centromere of a chromosome to which the microtubules bind (stabalises microtubules)
structure of mitotic spindle
the 3 types of microtubules (from cytoskeleton)
motor proteins attach spindles to chromosomes, connect to eachother for structure, radiate outwards (individually) for structure
metaphase
chromosomes continue to be organized by spindles + motor proteins
anaphase
seperation of chromosomes by spindles
seperatase (enzyme) cuts cohesions which cuts the tension + allows chromosomes to quickely seperate
anaphase A
chromosomes are pulled towards poles
anaphase B
spindle poles move away from eachother (cell elongates)
telophase
wrapping up, exit from mitosis
new nuclear envelopes formed for new daughter cells
cytokenesis
contractile ring forms out of actin microfilliments and cytoplasm devides into two new cells