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BIO107 - CELL AND MOLECULAR BIOLOGY > Cell cycle ( the cell cycle control system) > Flashcards

Cell cycle ( the cell cycle control system) Flashcards

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1
Q

operates like a timer that triggers the events of the cell cycle in a set sequence

A

cell-cycle control system

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2
Q

delay progression to M phase

A

malfunction

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3
Q

provide time for the machinery to be repaired and also prevent the disaster that
might result if the cycle progressed prematurely to the next stage

A

delay progression to M

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4
Q

based on a connected series of biochemical switches

A

cell-cycle control system

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5
Q

Where is cell-cycle control system based on?

A

connected series of biochemical switches

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6
Q

Each of connected series of biochemical switches possesses many important features that increase the?

A

accuracy and reliability of cell-cycle progression

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7
Q

the switches are in a irreversible fashion

A

binary (on/off)

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8
Q

irreversible fashion of switches would clearly be disastrous if?

A

if events like chromosome condensation or nuclear-envelope breakdown were only partially initiated or started but not completed.

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9
Q

the cell-cycle control system is remarkably _____ and _____ because backup
mechanisms allow the system to operate effectively under a variety of conditions

A

robust and reliable

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10
Q

remarkably robust and reliable, partly because of backup mechanisms

A

cell-cycle control system

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11
Q

highly adaptable and can be modified to suit specific cell types or to respond to
specific intracellular or extracellular signals.

A

cell-cycle control system

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12
Q

three major regulatory transitions

A
  1. Start (restriction point) in late G1
  2. G2/M transition
  3. metaphase-to-anaphase
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13
Q

cell commits to cell-cycle entry and
chromosome duplication

A

Start (restriction point) in late G1

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14
Q

Where do cell commits in Start (restriction point) in late G1

A

cell-cycle entry and chromosome duplication

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15
Q

Control system triggers the early mitotic events that lead to chromosome alignment on the mitotic spindle in metaphase

A

G2/M transition

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16
Q

control system stimulates sister-chromatid separation leading to the completion of mitosis and cytokinesis

A

metaphase-to-anaphase transition

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17
Q

G2/M transition triggers the early mitotic
events that lead to?

A

chromosome alignment on the mitotic spindle in metaphase

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18
Q

metaphase-to-anaphase stimulates
sister-chromatid separation, leading to

A

completion of mitosis and cytokinesis

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19
Q

What does the control system do if extracellular conditions are not appropriate for cell proliferation?

A

blocks progression through each of these
transitions if it detects problems inside or
outside the cell

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20
Q

Central components of the cell-cycle control system are members of a family of
protein kinases known as?

A

cyclin-dependent kinases (Cdks)

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21
Q

The activities of cyclin-dependent kinases (Cdks) ____ and ___as the cell progresses through the cycle

A

rise and fall

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22
Q

The rise and fall activities of Cdks lead to what

A

cyclical changes in the phosphorylation of intracellular proteins that initiate or regulate the major events of the cell cycle

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23
Q

Cdks are controlled by?

A

cyclins

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24
Q

four classes of cyclins

A
  1. G1/S-cyclins
  2. S-cyclins
  3. M-cyclins
  4. G1-cyclins
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25
Q

activate Cdks in late G1

A

G1/S-cyclin

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26
Q

what does G1/S-cyclin activaye

A

Cdks in late G1

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27
Q

bind Cdks soon after progression through Start and help stimulate chromosome duplication

A

S-cyclins

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28
Q

S-cyclins bind Cdks soon after progression
through?

A

Start

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29
Q

activate Cdks that stimulate entry to mitosis at the G2/M transition

A

M-cyclins

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30
Q

M-cyclins activate Cdks that stimulate
entry to?

A

mitosis at the G2/M transition

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31
Q

govern the activities of the G1/S-cyclins

A

G1-cyclins

32
Q

single Cdk protein binds all classes of cyclins

A

In yeast cells

33
Q

In yeast cells, a ___ Cdk protein binds all classes of ___

A

single
cyclins

34
Q

Have four Cdks

A

vertebrate cells

35
Q

How many Cdks interact with G1-cyclins in vertebrate cells?

A

Two

36
Q

Out of 4 Cdks in vertebrate cells, only 2 interacts with?

A

G1-cyclins

37
Q

How many Cdks interact with G1/S- and S-cyclins in vertebrate cells?

A

1

38
Q

Out of 4 Cdks in vertebrate cells, only 1 interacts with?

A
  1. G1/S- and S-cyclins
  2. S- and M-cyclins
39
Q

How many Cdks interact with S- and M-cyclins
in vertebrate cells?

A

1

40
Q

4 different cyclin–Cdk complexes

A
  1. G1-Cdk
  2. G1/S-Cdk
  3. S-Cdk, and
  4. M-Cdk
41
Q

How do different cyclin–Cdk complexes trigger different cell-cycle events?

A

Cyclin protein does not simply
activate its Cdk partner but also directs it to specific target proteins. As a result,
each cyclin–Cdk complex phosphorylates a different set of substrate proteins.

42
Q

phosphorylates a different set of substrate proteins

A

cyclin–Cdk complex

43
Q

in the absence of _____, active site in the Cdk protein is partly obscured by a protein loop

A

Cyclin

44
Q

in the absence of cyclin, the active site in the ____protein is partly obscured by a _____ ____

A

Cdk
protein loop

45
Q

causes the loop to move away from the active site, resulting in partial activation of the Cdk enzyme

A

Cyclin binding

46
Q

Cyclin binding causes the ___ to move away from the ____ ___, resulting in partial activation of the ___enzyme

A

loop
active site
Cdk enzyme

47
Q

occurs when a separate kinase, the Cdk-activating kinase (CAK), phosphorylates an amino acid near the entrance of the Cdk active
site.

A

full activation of the cyclin–Cdk

48
Q

Full activation of the cyclin–Cdk complex then occurs when ?

A

Cdk-activating kinase (CAK) phosphorylates an amino acid near the entrance of the Cdk active
site

49
Q

inhibits the activity of a cyclin–Cdk complex

A

Phosphorylation at a pair of amino acids in the roof of the kinase active site

50
Q

Phosphorylation of active site by ____ inhibits Cdk activity

A

Wee1

51
Q

_______ of active site by Wee1 inhibits Cdk activity

A

Phosphorylation

52
Q

dephosphorylation of these sites by _____ increases Cdk activity

A

Cdc25 phosphatase

53
Q

_____ of these sites by Cdc25 phosphatase
increases Cdk activity

A

dephosphorylation

54
Q

Binding of ___ ____ ____ inactivates cyclin–Cdk complexes.

A

Cdk inhibitor proteins (CKIs)

55
Q

Binding of Cdk inhibitor proteins (CKIs) inactivates?

A

cyclin–Cdk complexes

56
Q

progression through the metaphase- to-anaphase transition is triggered by ____ ____, leading to the final stages of cell division

A

protein destruction

57
Q

a member of the ubiquitin ligase
family of enzymes

A

anaphase-promoting complex or cyclosome
(APC/C)

58
Q

used in numerous cell processes to stimulate the proteolytic destruction of specific regulatory proteins

A

anaphase-promoting complex, or cyclosome (APC/C)

59
Q

APC/C are used in numerous cell processes
to stimulate the ______ ____of specific regulatory proteins. They _________ specific target proteins, resulting in their destruction in ______.

A

proteolytic destruction
polyubiquitylate
proteasomes

60
Q

The APC/C catalyzes the ubiquitylation and destruction two major types
of proteins :

A

securin
S- and M-cyclins

61
Q

protects the protein linkages that hold
sister-chromatid pairs together in early mitosis

A

securin

62
Q

What does securin protect?

A

protein linkages that hold
sister-chromatid pairs together

63
Q

destruction of securin

A

destroyed at metaphase

64
Q

destruction inactivates most Cdks in the cell

A

S- and M-cyclins

65
Q

many proteins phosphorylated by Cdks from S phase to early mitosis are ______

A

dephosphorylated

66
Q
  • ubiquitin ligase
  • ubiquitylate CKI
    proteins in late G1
  • destruction of G1/Scyclins in early S phase
A

SCF

67
Q

SCF is also responsible for the destruction
of?

A

G1/S-cyclins in early S phase

68
Q

changes in its association
with an activating subunit—either Cdc20 in mid-mitosis or Cdh1 from late mitosis through early G1.

A

APC/C activity

69
Q

APC/C activity
changes during the cell cycle, primarily as a result of changes in its association
with an activating subunit—either?

A

Cdc20 in mid-mitosis or Cdh1 from late mitosis through early G1

70
Q
  • depends on substrate-binding subunits called F-box proteins.
  • constant during the cell
    cycle
A

SCF activity

71
Q

SCF activity depends on substrate-binding subunits called?

A

F-box proteins

72
Q

cell-cycle depends exclusively on
post-transcriptional mechanisms that involve the regulation of Cdks and ubiquitin ligases and their target proteins

A

in early animal embryos

73
Q

in early animal embryos cell-cycle control depends exclusively on?

A

post-transcriptional mechanisms

74
Q

In the more complex cell cycles of most cell types, ______ ____provides an important additional level of regulation

A

transcriptional control

75
Q
A

BIO107 - CELL AND MOLECULAR BIOLOGY (16 decks)

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