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Cell Bio > Chapter 18 > Flashcards

Chapter 18 Flashcards

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Biology 101 flashcards
1
Q

Cell cycle phases

A

M, G1, G2, S

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2
Q

Most cell cycle duration differences are due to the

A

legnth if gap phases

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3
Q

Cells can also exit the cell cycle for an extended time by entering

A

G0 phase

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4
Q

What must be met before the cell cycle can transition to the next phase

A

Checkpoints

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5
Q

must bind cyclins to become
activated and phosphorylate their
target proteins

A

Cyclin-dependent kinases (CDKs)

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6
Q

Cdk regulation is carried out by

A

phosphorylation

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7
Q

Drives the cyclic assembly and activation of cyclin-Cdk complexes

A

Changes in the concentration of cyclin

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8
Q

The cell-cycle control system depends on

A

cyclin accumulation and degradation

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9
Q

Continual transcription leads to a gradual increase in the

A

concentration of each cyclin over the course of the cell cycle

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10
Q

Abrupt degradation of cyclins returns the Cdks to an

A

inactive state

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11
Q

Degradation of cyclins occurs via the

A

proteasome

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12
Q

Cyclins are tagged with a chain of ubiquitin by an enzyme called
the

A

anaphase-promoting complex (APC/C)

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13
Q

To activate a Cdk, two conditions must be met:

A

(1) The Cdk must bind a cyclin to form a cyclin-Cdk complex
2. each cyclin-Cdk complex must be
dephosphorylated

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14
Q

Cdk activity can also be blocked by the

A

binding of a Cdk inhibitor

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15
Q

M-Cdk is inhibited by phosphorylation via the

A

kinase Wee1

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16
Q

M-Cdk is activated by dephosphorylation by the

A

phosphatase Cdc25

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17
Q

what is the target if phosphorylation

A

Cdk (not cyclin)

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18
Q

Cdk activity thus requires both ___ on inhibitory sites

A

cyclin binding and dephosphorylation

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19
Q

To progress into mitosis, M-Cdk must be
dephosphorylated by

A

Cdc25

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20
Q

Once M-Cdk is activated it phosphorylates and activates nore Cdc25 which ___, it is a __ feedback loop, and increase in M-Cdk activity at the start of __

A

dephosphorylates, positive, M phase

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21
Q

important to
prevent transmission of
mutations or inaccurate
chromosome separation

A

checkpoint

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22
Q

Protein kinases respond to
DNA damage by
phosphorylating and
activating

A

p53

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23
Q

activates transcription of a Cdk inhibitor

A

p53

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24
Q

p53 is an important…

A

tumor suppressor gene, it many cancers

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25
Q

If the damage cannot be
repaired, p53 causes the
cell to

A

die

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26
Q

Match the scenario with the outcome:
___ The cell detects that its DNA is not fully replicated.
____ The cell detects that its chromosomes are not properly attached to the mitotic spindle.
Outcomes:
(a) The cell would delay entry into M phase
(b) The cell would delay exit from M phase.

A

a
b

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27
Q

Match the scenario with the outcome:
____ The cell lacks a protein required for a checkpoint mechanism that operates in G2
____ The cell lacks a protein required for a checkpoint mechanism that operates in G1

Outcomes:
(a) The cell would enter S phase under
conditions when normal cells would
not.
(b) The cell would enter M phase under
conditions when normal cells would not.

A

b
a

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28
Q

the cell reorganizes and distributes its
components equally into two daughter cells in what phase

A

M phase

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29
Q

M phase includes

A

mitosis and cytokinesis

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30
Q

pulls the duplicated chromosomes apart
during mitosis

A

mitotic spindle

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31
Q

divides the cytoplasm into two halves
during cytokinesis

A

contractile ring

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32
Q

Mitosis occurs in __ stages

A

5

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33
Q

Before M phase when events must take place

A

The cell’s DNA must be fully replicated, The centrosome must be
duplicated

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34
Q

Replicated chromosomes are held together at the

A

centromere

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35
Q

Before entering mitosis, sister chromatids

A

condense

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36
Q

Sister chromatids are held
together by protein complexes
called

A

cohesins

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37
Q

are protein complexes that help carry out
chromosome condensation

A

condensins

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38
Q

Phosphorylation of condensins by M-Cdk triggers the
assembly of

A

condensin complexes onto the DNA

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39
Q

The duplicated centrosomes become

A

spindle poles

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40
Q

New microtubules grow out from the
spindle poles and form the

A

mitotic spindle

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41
Q

originate from one spindle pole and interact with
microtubules from the other spindle pole

A

Interpolar microtubules

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42
Q

originate in random directions from either spindle pole and do
not interact with other microtubules

A

Astral microtubules

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43
Q

bind the kinetochores of duplicated chromosomes

A

Kinetochore microtubules

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44
Q

are protein complexes that form on the centromere of each
chromosome, attach to the plus end of microtubules

A

kinetochores

45
Q

Before M phase begins, two critical events must be completed

A

1) The DNA of the chromosomes is replicated
2) The centrosome is duplicated

46
Q

Interphase consists of what other phases

A

G1, S, G2

47
Q

What phase: chromosomes condense, kinetochores assemble onto chromosomes

A

Prophase

48
Q

What phase: The mitotic spindle assembles between the two centrosomes

A

Prophase

49
Q

Phosphorylation of condensins by MCdk promotes…

A

prophase

50
Q

are protein complexes that help carry out chromosome condensation

A

Condensins

51
Q

Phosphorylation of condensins by MCdk triggers the assembly of

A

condensin complexes on DNA

52
Q

Mitosis stage 2:

A

Prometaphase

53
Q

What phase: The nuclear envelope breaks down and microtubules of mitotic spindle attach kinetochores on chromosomes

A

Prometaphase

54
Q

Phosphorylation of nuclear lamins promotes

A

nuclear envelope breakdown during prometaphase

55
Q

Mitosis stage 3:

A

metaphase

56
Q

What phase: The chromosomes are aligned midway between the spindle poles, The kinetochore microtubules on each sister chromatid attach to
opposite poles of the spindle

A

Metaphase

57
Q

Mitosis stage 4

A

anaphase

58
Q

What phase: The sister chromatids separate and are pulled toward the
spindle pole to which they are attached

A

anaphase

59
Q

What phase: The kinetochore microtubules shorten, and the spindle poles
also move apart

A

anaphase

60
Q

During anaphase, degradation of cohesin allows…

A

chromosome segregration

61
Q

Sister chromatids are held
together by protein complexes
called

A

cohesins

62
Q

The cohesin linkage during anaphase is destroyed by a protein called

A

separase

63
Q

Before anaphase, separase is held in an active state by

A

securin

64
Q

At the beginning of anaphase, securin is targeted for degradation by

A

APC/C

65
Q

Anaphase A or B
spindle poles are pushed and pulled apart
kinetochore microtubules shorten, moving chromosomes
toward spindle poles

A

B
A

66
Q

Mitosis stage 5:

A

Telophase

67
Q

What phase: The two sets of chromosomes arrive at the spindle poles, a new nuclear envelope reassembles around each set of
chromosomes

A

Telophase

68
Q

Dephosphorylation of nuclear lamins allows

A

reassembly of the nuclear envelope during telophase

69
Q

What divides the cell into 2

A

cytokinesis

70
Q

The cytoplasm is divided in two by a ____

A

contractile ring of actin
and myosin

71
Q

contractile ring of actin and myosin

A

contractile ring

72
Q

Sliding of actin filaments against the myosin filaments generates a
force that creates a

A

a cleavage furrow and divides the cell in two

73
Q

Match the stage of M phase to the events that occur during
that stage:
___ Alignment of the chromosomes at the spindle equator
___ Breakdown of the nuclear envelope
___ Pinching of the cell in two
___ Re-formation of the nuclear envelope
___ Condensation of the chromosomes
___ Separation of sister chromatids

A. prophase
B. prometaphase
C. metaphase
D. anaphase
E. telophase
F. cytokinesis

A

C
B
F
E
A
D

74
Q

Kinetochores assemble on what region of chromosome

A

centromere

75
Q

If cells are no longer needed, they can remove themselves via

A

apoptosis

76
Q

Cell death plays a critical role during

A

animal/body development

77
Q

In adults, the rate of cell death = the rate of __

A

cell proliferation

78
Q

Apoptosis allows cells to die __

A

individually

79
Q

engulf the apoptotic cell before its contents can leak out

A

Phagocytic cells

80
Q

cells that die as a result of
acute injury undergo

A

necrosis

81
Q

The cell swells and bursts is

A

necrosis

82
Q

This triggers a potentially damaging
inflammatory response

A

necrosis

83
Q

proteases that are responsible for apoptosis

A

Caspases

84
Q

Caspases are made as inactive precursors called

A

procaspases

85
Q

cleave and activate executioner caspases

A

Initiator caspases

86
Q

Procaspases are activated in response to signals that

A

induce apoptosis

87
Q

Active executioner caspases __ many proteins in the cell

A

degrade

88
Q

control release of the protein cytochrome c from
mitochondria into the cytosol

A

Bcl2 family proteins

89
Q

Caspase activity is tightly regulated by the

A

Bcl2 family of proteins

90
Q

Two Bcl2 family members, ___ and ___ , promote cytochrome c release. Other family members inhibit release.

A

Bax and Bak

91
Q

Once released into the cytosol, cytochrome c activates initiator
procaspases by promoting the assembly of a large protein complex called
the

A

apoptosome

92
Q

In a multicellular organism, the fate of individual
cells is controlled by

A

signals from other cells

93
Q

Three major categories of signal proteins

A

Survival factors promote cell survival
* Mitogens stimulate cell division
* Growth factors stimulate cell growth

94
Q

Survival factors usually act through

A

cell surface receptors

95
Q

When survival factors cell surface receptors are activated, they turn on intracellular signaling pathways that…

A

inhibit apoptosis

96
Q

Most survival factors activate signaling pathways that regulate members
of the

A

Bcl2 family

97
Q

stimulate cell division by promoting
entry into S phase

A

Mitogens

98
Q

Most mitogens are secreted proteins that bind

A

cell-surface
receptors

99
Q

Mitogens intracellular signaling pathways act mainly by

A

promoting the
transition from G1 phase into S phase

100
Q

some factors can act as both __ and __
by promoting both cell growth and division

A

mitogens and growth factors

101
Q

binds transcription regulators and prevents them
from turning on genes required for cell division

A

Retinoblastoma protein (Rb)

102
Q

Mitogens trigger the activation of

A

G1-Cdk and G1/S-Cdk

103
Q

Role of G1-Cdk and G1/S-Cdk

A

phosphorylate Rb protein

104
Q

phosphorylate Rb protein alters the ___ of Rb and it releases ___ so that it can activate ___ required for ___ into __ phase

A

conformation, bound transcription regulators so they can activate genes required for entry into S phase

105
Q

promote the
accumulation of proteins and other
macromolecules

A

Growth factors intracellular signaling pathway

106
Q

promote protein synthesis and inhibit protein degradation

A

Growth factors

107
Q

Binding of a growth factor to a
receptor tyrosine kinase (RTK) initiates an
intracellular signaling pathway that leads to
activation of

A

Akt and Tor

108
Q

Example of what stimulates
protein synthesis and inhibits protein
degradation

A

Akt and Tor

Cell Bio (15 decks)

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