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Chapter 18 Flashcards

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Biology 101 flashcards
1
Q

3 basic steps of the cell cycle

A
  1. cell growth and chromosome duplication
  2. chromosome segregation
  3. cell division
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2
Q

M phase definition

A

period of the eukaryotic cell cycle during which the nucleus and cytoplasm divide to produce two daughter cells

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3
Q

interphase definition

A

long period of the cell cycle between one mitosis and the next
includes G1, S, and G2 phases

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4
Q

S phase definition

A

period during a eukaryotic cell cycle in which DNA is synthesized

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5
Q

G1 phase definition

A

Gap 1 phase of the eukaryotic cell cycle; falls between the end of cytokinesis and the start of DNA synthesis

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6
Q

G2 phase definition

A

Gap 2 phase of the eukaryotic cell cycle; falls between the end of DNA synthesis and the beginning of mitosis

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7
Q

three main transition points of cell-cycle control regulation

A

late G1 phase to confirm the environment is favorable (sufficient nutrients and specific signal molecules)
G2 to M phase to confirm that the DNA is undamaged and full replicated
midway through mitosis confirms the duplicated chromosomes are attached to the mitotic spindle correctly

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8
Q

start definition

A

important transition at the end of the G1 phase of the eukaryotic cell cycle; passage through this transition commits the cell to enter the cell cycle and continue to S phase

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9
Q

cell-cycle control system definition

A

network of regulatory proteins that govern the orderly progression of a eukaryotic cell through the stages of cell division

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10
Q

one of the most common ways by which cells switch the activity of a protein on and off

A

phosphorylation followed by dephosphorylation

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11
Q

phosphorylation reactions that control the cell cycle are carried out by _____

A

protein kinases

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12
Q

dephosphorylation reactions that control the cell cycle are carried out by ______

A

protein phosphatases

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13
Q

cyclin definition

A

regulatory protein whose concentration rises and falls at specific times during the eukaryotic cell cycle
help control progression from one stage of the cell cycle to the next by binding to cyclin-dependent protein kinases (Cdks)

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14
Q

Cdk (cyclin-dependent protein kinase) definition

A

enzyme that, when complexed with a regulatory cyclin protein, can trigger various events in the cell-division cycle by phosphorylating specific target proteins

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15
Q

When is cyclin concentrations high and low?

A

high during mitosis
low during interphase
vary in a cyclical fashion

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16
Q

M-cyclin definition

A

regulatory protein that binds to mitotic Cdk to form M-Cdk, the protein complex that triggers the M phase of the cell cycle

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17
Q

M-Cdk definition

A

protein complex that triggers the M phase of the cell cycle; consists of an M-cyclin plus a mitotic cyclin-dependent protein kinase (Cdk)

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18
Q

G1/S-cyclin definition

A

regulatory protein that helps to launch the S phase of the cell cycle

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19
Q

S-cyclin definition

A

regulatory protein that helps to launch the S phase of the cell cycle

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20
Q

G1/S-Cdk definition

A

protein complex whose activity triggers entry into S phase of the cell cycle; consists of a G1/S-cyclin plus a cyclin-dependent protein kinase (Cdk)

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21
Q

S-Cdk definition

A

protein complex whose activity initiates DNA replication; consists of an S-cyclin plus a cyclin-dependent protein kinase (Cdk)

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22
Q

G1-cyclin definition

A

regulatory protein that helps drive a cell through the first gap phase of the cell cycle and toward S phase

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23
Q

G1-Cdk definition

A

protein complex whose activity drives the cell during the first gap of the cell cycle; consists of a G1-cyclin plus a cyclin-dependent protein kinase (Cdk)

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24
Q

anaphase-promoting complex (APC/C) definition

A

a protein complex that triggers the separation of sister chromatids and orchestrates the carefully timed destruction of proteins that control progress through the cell cycle; the complex catalyzes the ubiquitylation of its targets

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25
Q

how does the cyclin-Cdk complex becomes activated

A

Cdk must be dephosphorylated by a specific protein phosphatase

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26
Q

Cdk inhibitor protein definition

A

regulatory protein that blocks the assembly or activity of cyclin-Cdk complexes, delaying progression primarily through the G1 and S phases of the cell cycle

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27
Q

regulators that oppose Cdk

A

family of phosphatases called PP2A

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28
Q

control system uses ____ in late G1 phase to keep cells from entering the cell cycle

A

Cdk inhibitors

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29
Q

what control system occurs at the G2 to M transition

A

suppresses the activation of the M-Cdk by inhibiting the phosphatase required to activate the Cdk

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30
Q

what control system delays chromosome segregation in mitosis

A

inhibiting the activation of APC/C, preventing the degradation of M-cyclin

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31
Q

what must be inactivated for the cell to go from M phase to G1

A

S-Cdk
M-Cdk

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32
Q

mammalian cells will multiply only if they are stimulated to do so by _____

A

mitogens

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33
Q

Mitogens act by switching on the cell signaling pathways that stimulate the synthesis of _____, ______, and ______

A

G1-cyclins
G1/S-cyclins
other proteins involved in DNA synthesis and chromosome duplication

34
Q

what do retinoblastoma (Rb) proteins do

A

binds to particular transcription regulators and prevents them from turning on genes required for cell proliferation

35
Q

p53 definition

A

transcription regulator that controls the cell’s response to DNA damage, preventing the cell from entering S phase until the damage has been repaired or inducing the cell to commit suicide if the damage is too extensive

36
Q

S-Cdk initiates _____ and blocks _______

A

DNA replication
re-replication

37
Q

what two proteins/protein complexes position the DNA helicases

A

origin recognition complex (ORC)
Cdc6

38
Q

how does S-Cdk prevent re-replication

A

phosphorylates Cdc6 and the ORC to inactivate the proteins

39
Q

what needs to be done in the control cycle to move into M phase

A

inhibitory phosphates must be removed from M-Cdk by activating protein phosphatase (Cdc25)

40
Q

what are the two main components of M phase

A

mitosis and cytokinesis

41
Q

____ prepares the duplicated chromosomes for segregation and induces the assembly of the mitotic spindle

A

M-Cdk

42
Q

M-Cdk complexes are reinforcing so they can indirectly…

A

turn on additional M-Cdk complexes

43
Q

Trend of M-Cdk levels durong G2 and M phase

A

accumulate in G2 but aren’t activated until end of G2

44
Q

what controls the exit from mitosis

A

activated M-Cdk turns on APC/C which after a delay, directs the destruction of M-cyclin and inactivates M-Cdk

45
Q

sister chromatid definition

A

copy of a chromosome, produced by DNA replication, that still remains bound to the other copy

46
Q

cohesion definition

A

ring-shaped SMC protein complex that organizes interphase chromosomes into a long series of chromatin loops
holds together the sister chromatids after DNA has been replicated

47
Q

what is the term for mis-segregation that can lead to abnormal numbers of chromosomes

A

aneuploidy

48
Q

condensin definition

A

ring-shaped SMC protein complex that compacts duplicated chromosomes for segregation by forming both loops and loops within loops

49
Q

difference between cohesins and condensins

A

cohesins: encircle the sister chromatids, tying them together
condensins: assemble along each sister chromatid, helping each of these double helices to coil up into a more compact form

50
Q

the ________ divides the entire cell in two during cytokinesis

A

contractile ring

51
Q

two critical events that must be completed before M phase begins

A

DNA must be fully replicated
centrosome must be duplicated

52
Q

centrosome definition

A

microtubule-organizing center that sits near the nucleus in an animal cell
during the cell cycle, this structure duplicates to form the two poles of the mitotic spindle

53
Q

aster definition

A

star-shaped array of microtubules emanating from a centrosome or from a pole of a mitotic spindle

54
Q

mitotic spindle definition

A

array of microtubules and associated molecules that forms between the opposite poles of a eukaryotic cell during mitosis and pulls apart duplicated chromosome sets

55
Q

spindle pole definition

A

centrosome from which microtubules radiate to form the mitotic spindle

56
Q

what occurs before M phase

A

cell increases in size
DNA of the chromosomes is replicated
centrosome is duplicated

57
Q

what occurs in prophase

A

sister chromatids condense
mitotic spindle assembles between two centrosomes outside the nucleus

58
Q

what occurs in prometaphase

A

breakdown of the nuclear envelope
chromosomes attach to spindle microtubules via kinetochores

59
Q

what occurs in metaphase

A

chromosomes are aligned at the equator of the spindle
kinetochore microtubules attach to opposite poles of the spindle

60
Q

what occurs in anaphase

A

sister chromatids separate and are pulled slowly towards the spindle pole

61
Q

what occurs in telophase

A

two sets of chromosomes arrive at the poles of the spindle
new nuclear envelope reassembles around each set
contractile ring starts to form

62
Q

what occurs in cytokinesis

A

cytoplasm is divided in two by a contractile ring

63
Q

kinetochore definition

A

protein complex that assembles on the centromere of a condensed mitotic chromosome; the site to which spindle microtubules attach

64
Q

a continuous balanced additional and loss of ____ subunits is required to maintain the metaphase spindle

A

tubulin

65
Q

what protease destroys the cohesion linkage

A

seperase

66
Q

before anaphase begins, seperase is held in an inactive state by an inhibitory protein called ____

A

securin

67
Q

what happens in anaphase A

A

chromosomes move poleward
kinetochore microtubules shorten

68
Q

what happens in anaphase B

A

spindle poles are pushed and pulled apart

69
Q

what happens at the spindle assembly checkpoint

A

kinetochores send a “stop” signal to block the activation of APC/C

70
Q

contractile ring definition

A

structure made of actin and myosin filaments that forms a belt around a dividing cell, pinching it in two

71
Q

phragmoplast definition

A

in a dividing plant cell, structure containing microtubules and membrane vesicles that guides the formation of a new cell wall

72
Q

what do mitogens do

A

stimulate cell division, primarily by overcoming the intracellular braking mechanisms that block progression through the Start transition and entry into the cell cycle in late G1

73
Q

what do growth factors do

A

stimulate cell growth by promoting the synthesis and inhibiting the degradation of proteins and other macromolecules

74
Q

what do survival factors do

A

promote cell survival, largely by suppressing apoptosis

75
Q

mitogens are secreted signal proteins that bind to _______

A

cell-surface receptors

76
Q

most extracellular growth factors bind to ______ that activate intracellular signaling pathways

A

cell-surface receptors

77
Q

capase definition

A

one of a family of proteases that, when activated, mediates the destruction of the cell by apoptosis

78
Q

what are the two types of capases that work together to take a cell apart

A

initiator capases
executioner capases

79
Q

two important death-inducing proteins from the Bcl2 family

A

Bax
Bak

80
Q

cytochrome c molecule released from mitochondria activate ______

A

initiator capases and induce apoptosis by promoting the assembly of apoptosome

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