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Cell biology > lecture 7 > Flashcards

lecture 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

cerveisiae life cycle

A
  • after spindle pole body duplication, bud emergence
  • bug dets progressively larger and then chromosome segregation and cytokinesis
  • produces a mother celll (regular size) and a much smaller daughter cell that will get larger and grow and then undergo the same process
  • spends longer in g1
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2
Q

sombe life cycle

A

fission yeast
- starts with DNA replciation
- rod gets longer and longer
- formation of septum (cytogenesis occurs through this)
- divides into two equal sized cells
- distinct moropholical features at every stage can be used to idnietify what stage of cell cycle its at.
- spends longer in g2 and M phases

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3
Q

cdc

A

cell division cycle mutants, both cerevisae and pombe have temperature sensitive mutants which cause defects in spefici proteins required to progress through the cell cycle.

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4
Q

loss of cdc 2 activity in s. pombe

A

prevents entering into M phase

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5
Q

cdc 2

A

a cyclin dependent kinase (CDK)

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6
Q

cdc 2 in cerevisiae = cdc ____ in pombe

A

28

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7
Q

are proteins controlling cell cycle highly conserved between eukaryotic organisms

A

yes; human CDKs can be used in yeast cells with mutations to gain functional CDKs

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8
Q

kinases

A
  • put phosphate gorps on
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9
Q

phosphatases

A

remove phosphate groups from proteins

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10
Q

MPF

A
  • heterodimer of CDK an mitotic cyclin (cdc 2)
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11
Q

cdc 2 activity

A
  • is not active, phosphorylation activity remains low at G1-S phase and increases towards G2 phase, peaking at the start of mitosis
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12
Q

cdc 2 presence/amount

A
  • remains constant
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13
Q

what does a western blot of the cdc 2 and cyclin samples show?

A
  • mitotic cyclin bands are greater at one point in cell cycle and disappear and then reappear. (peals at G2,drops off during mitosis and then increases and drops off at that point gain)
  • cdc 2 bands remain constant
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14
Q

does cyclin have enzymatic activity

A
  • no but it associates with a kinase that does
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15
Q

activity of mitosis promoting factor

A
  • peaks at late g2, and drops off
  • this correlates with levels of cclin
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16
Q

what is the dotted line

A

it is the level of cyclin (red is the activity of cdc 2)
- beings low in g1 and then increases and peaks in late G2 and then drops off
- having more cyclin present may turn on cdc atvitiy

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17
Q

when does MPF form

A
  • late g2, cdc 2 binds cyclin to form and activate MPF
18
Q

why is it that there is a lot of cyclin in s phase but no cdc 2 activity

A

more than one type of cyclin? there must another level of regulation?

19
Q

when are cyclins presnt

A
  • ## at the cell cycle stage that they trigger and are absent in other cell cycle stages.
20
Q

what are the types of cyclin

A

G1, G1/S, S and mitotic

21
Q

how are cyclins regulate

A
  • transcription factors that cn turn on at diff phases of the cel cycle
  • ubiquitin mediated proteasome dependent degradation
22
Q

what is ub-mediated proteasome-dependent degradation

A
  • degrades the cyclins when no longer needed
23
Q

ub

A

76 amino acid protein
- found in all eukaryotic clls

24
Q

polyubiquitination

A
  • of a target protein acts as a signal for the targeted protein to be degraded by the proteosome
  • proteins are now directed towards “garbage can”
  • degradative enzymes isnide
  • ate hydrolysis required to move the protein and ub to proteasome for degradation
  • all cyclins are destroyed at certain phases of the cell cycle
25
Q

what happens t ub proteins when autophagy doesn’t work

A
  • acclamation of UB proteins
26
Q

SCF uniqutuinin ligaes

A
  • target cyclins for destruction by ub at certain phases of the cell cycle
27
Q

is ub degraded in the proteosome

A

no

28
Q

wee1

A

kinase phpsorylates CDK, causing it to be activated adds phosphate group at tyrosine pos 15

29
Q

cdc25

A

phosphatase that removes the inhibitory phosphate group from CDK and promote sits activation

30
Q

what regulates MPF activty

A

wee1 and cdc25 by addition ore removal of phosphate groups on CDK, removes the phosphate pout on by wee1 kinase, allowing MPF (cyclin idk complex to be fully activated)

31
Q

mutation in wee1 kinase or excess of cdc 25

A
  • phosphate group not added to CDK
  • increase in mitotyic cyclin during s pace and g2
  • premature trigger tino mitosis (cells dot expand and elongate), small cells because of decreased G2 no break from addition of phosphate group
  • cell enters mitosis too early
    same phenotype as if there was an excess of cdc 25 (removing the phsppahte group right away)
32
Q

mutation in phpshatase so that it is no longer functional

A
  • phosphate group remains on
  • cell grows and grows but does not. have signal to enter mitosis
  • elongated cells that are stuck in g2 and cannot go to mitosis
    this might also happen if too much/too active wee1 kinase putting on phosphate groups
33
Q

another Layer of regulation after cdc 25 removes phosphate grou

A
  • CAK puts a phosphate group at threonine 161 on CDK
34
Q

what are all the components needed for MPF to be active

A
  • sufficient mitotic cyclin synehtsized
  • associate it with CDK
  • inactivation phspph group at tyr 1,5 removal by cdc 25, and then
  • acting phosphate grou by CAK at thr 161
35
Q

CAK

A

an activating kinase

36
Q

active MPF rols

A
  • chrom condenation, disassembly of nuclear envelope, interpose microtubule dissamebly and mitotic spindle formation (MAP)
  • remodeling Golgi, er

basically CDK kinase phosphorylation leads to the proomtoion of cell to enter mitosis

37
Q

when does inactivation of MPF

A
  • inactivation at anaphase needed
38
Q

mechanism for inactivating MPF

A
  • rapid mitotic cyclin degradation after polyuiquintainon
  • requires APC (anaphase promotic complex/cyclosome)
39
Q

APC

A

ub ligase active at end of mitosis.
- sticks on ub molecules onto mitotic cyclin to promote degradation of the cell

40
Q

how do ub ligases (like APC) know where to stick on ub

A
  • ## destruction box (nine amino acids found in cyclins), helps promote rdestrucftion of proteins by the proteosome, and recognition by ligases
41
Q

is CDK polyubiqtuianteed ?

A

NO but cannot have high activity without the mitotic cyclin after anaphase

42
Q
A

Cell biology (15 decks)

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