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Biochemistry > Exam 4: Cell Cycle > Flashcards

Exam 4: Cell Cycle Flashcards

(55 cards)

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1
Q

M phase

A

Mitosis - cell divides into two daughter cells

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2
Q

Interphase

A

time between mitosis

G1, S, and G2 phases

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3
Q

G1 phase

A

growth period precedes DNA synthesis

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4
Q

S phase

A

DNA is replicated only one time

At end, each chromosome has two identical sister chromatids linked by centromere

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5
Q

G2 phase

A

Second period of growth that precedes cell division

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6
Q

G0

A

cells are differentiated and no longer dividing

exited cell cycle, some cells can re-enter cell cycle when stimulated

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7
Q

G1/S checkpoint

A

start or restriction point

cell determines if conditions are favorable for division

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8
Q

G2/M checkpoint

A

ensures that all DNA has been replicated

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9
Q

Metaphase/anaphase transition point

A

All chromosomes are evaluated to ensure they are attached to mitotic spindle

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10
Q

DNA damage checkpoint

A

throughout cell cycle, detects damage to DNA

Cells with damaged DNA arrest until repairs are made, if damage can’t be repaired, cell enters apoptotic pathway

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11
Q

cyclin-dependent kinases (CDKs)

A

enzymes that function in association with regulatory subunits - cyclins
Active at different stages of cell cycle and regulate progression through phosphorylation of different protein targets

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12
Q

M phase uses what cyclin/CDK complex

A

Cyclin A/CDK1 and Cyclin B/CDK1

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13
Q

Mid G1 phase uses what cyclin/CDK complex

A

Cyclin D/CDK4 & 6

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14
Q

Late G1 phase uses what cyclin/CDK complex

A

Cyclin E/CDK2

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15
Q

S phase uses what cyclin/CDK complex

A

Cyclin A/CDK2

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16
Q

mitogenic signals

A

tissue-specific growth factors required to stimulate cell growth and division
Must overcome controls (like restriction point) in order to promote proliferation in most cells

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17
Q

Interactions between cell and extracellular matrix

A

promote cell division

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18
Q

Interactions between neighboring cells

A

inhibit cell division - contact inhibition

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19
Q

early response genes

A

genes transcribed in initial phase of cell, after adding growth factor

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20
Q

c-Fos transcription factor

A

early-response gene
stimulates transcription of the delayed-response genes (other transcription factors, mid-G1 cyclins & CDKs, late G1 cyclins)
transcription of c-Fos stimulated by MAP kinase cascade

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21
Q

growth factor binds to receptors containing

A

tyrosine kinase activity - triggers autophosphorylation of tyrosine residues, forms a docking site for other signaling molecules

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22
Q

GRB2

A

binds to phosphotyrosine residues on activated growth factor receptor
binds protein Sos, bringing it to cell membrane

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23
Q

Sos

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A

brought to cell membrane by binding with GRB2 on growth factor receptor
interacts with Ras - promotes exchange of GDP to GTP activating Ras

24
Q

Ras

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A

small G-protein
inactive in GDP-bound form, active in GTP-bound form
Activated by Sos
Activates protein kinase Raf

25
Raf
protein kinase activated by active Ras | phosphorylates/activates MAP kinase kinase
26
MAP kinase kinase
activated by active Raf | phosphorylates/activates MAP kinase
27
MAP kinase
activated by MAP kinase kinase enters nucleus and regulates transcription of many genes stimulates c-Fos transcription, which leads to progression through restriction point
28
Rb (retinoblastoma protein)
binds to protein products of delayed-response genes, E2F proteins, act as transcriptional repressors & inhibit transcription
29
E2F proteins
protein products of delayed-response genes transcription factors - activating transcription of many genes required for DNA replication stimulate transcription of late G1 cyclin (cyclin E), S phase cyclin (cyclin A), S phase CDK (CDK2) Inactive when bound to Rb
30
Cyclin D-CDK4/6
Mid G1 phase cyclin/CDK complex Promotes cell cycle growth by phosphorylating Rb, causing dissociation from E2F & activating E2F for transcription of genes & readying cell for S phase Late G1 phase cyclin/CDK complex (cyclin E-CDK2) produced
31
Cyclin E-CDK2
Late G1 phase cyclin/CDK complex continues phosphorylation of Rb, promoting entry of cell into S phase phosphorylates p27 triggers proteolysis of inhibitor & activation of Cyclin A-CDK2 complex
32
INK4 proteins
compete with cyclin D for binding to CDK 4/6, act as specific inhibitor of CDK 4/6 activity
33
p27 (KIP1)
inhibits cyclin A-CDK2 complex (keeps it in inhibitory state) forms complex with cyclin A-CDK2 - frees complex when phosphorylated
34
Cyclin A-CDK2
S phase cyclin/CDK complex inhibited by forming complex with p27 (phosphorylated by cyclin E-CDK2) Also requires dephosphorylation of internal inhibitor to be activated When activated, DNA replication can begin - phosphorylates components of origins of replication to promote initiation of DNA replication
35
Cyclin A/B-CDK1
M phase cyclin/CDK complex held in inactive phase due to inhibitory phosphorylation of CDK 1 subunit until DNA replication is complete Dephosphorylation activates complex - phosphorylates many substrates responsible for driving early part of mitosis (chromosome condensation, formation of mitotic spindle, and disassembly of nuclear membrane)
36
Anaphase promoting complex
activated by attachment of chomosomes to mitotic spindle leads to degradation of cohesion complexes that hold sister chromatids together at centromere polyubiquinates cyclin A & B after anaphase is complete
37
ATM
G2/M checkpoint protein kinase detects replication forks - recognizes that DNA synthesis is still in progress prevents dephosphorylation/activation of cyclin/CDK1 complexes Also works with ATR as a DNA damage checkpoint; responds to double-stranded DNA breaks
38
inhibition of anaphase promoting complex
by protein factors that recognize kinetochores not associated with spindle
39
ATM/ATR
DNA damage checkpoints inhibits phosphatases that normally dephosphorylate and activate cyclin/CDK2 and cyclin/CDK1 complexes - block progression of cell cycle Phosphorylates/stabilizes p53
40
ATR
DNA damage checkpoint | activated by DNA damage caused by UV light and certain drugs
41
p53
transcription factor stabilized from phosphorylation by activation of ATM/ATR Activates p21, which inhibits both cyclin/CDK1 and CDK2 complexes - prevents cell growth Intrinsic activator of apoptosis
42
p21
inhibitor of cyclin-dependent kinases | inhibits both cyclin/CDK1 and cyclin/CDK2 complexes - blocks S phase and mitosis
43
Ataxia-telangiectasia
inherited disorder, difficulty in coordination of movement, small wide blood vessels, more susceptible to infection & chronic lung infections, leukemias, & lymphomas, highly sensitive to radiation exposure Caused by mutation in gene encoding ATM - cell response to double strand DNA breaks is impaired
44
Apoptosis
programmed cell death removes damaged or infected cells from body normal cell turnover, embryonic development & functioning of immune system key means by which cytotoxic chemicals in cancer therapy work Chromosome condenses, cell shrinks in size, nuclear envelope breaks up, cell fragmentation and blebbing occur (forming apoptotic bodies, which are then phagocytosed)
45
tumor necrosis factor (TNF)
produced by macrophages & play role in cell death and tissue destruction - seen in chronic inflammatory diseases
46
Fas ligand
produced by natural killer cells and cytotoxic T-lymphocytes
47
caspases
family of proteases that are present as inactive precursors until apoptotic signal recieved Initiator caspases activated by apoptotic signal and activate executioner caspases - hydrolyze cellular proteins & trigger DNA fragmentation
48
Bcl-2 family
family of proteins involved in apoptosis - proapoptotic proteins PUMA, BID, BAX
49
Bcl-2
antiapoptotic protein outer mitochondrial membrane protein inhibits BAX
50
BAX
protein that can form a channel in mitochondrial outer membrane when stimulated allows release of cytochrome c from mitochondria into cytoplasm
51
PUMA & BID
function to stimulate BAX activity
52
Apaf-1
when bound to cytochrome c (released from mitochondria by BAX) it oligomerizates - results in formation of apoptosome
53
apoptosome
formed by activation of Apaf-1 by cytochrome c | recruits and activates initiator caspase, caspace-9
54
Caspase-9
initiator caspase activated by apoptosome activates caspase-3, executioner caspase
55
Caspase-3
executioner caspase activated by caspase-9 sets cell down path of programmed cell death

Biochemistry (15 decks)

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