Chapter 18 Flashcards
(108 cards)
1
Q
Cell cycle phases
A
M, G1, G2, S
2
Q
Most cell cycle duration differences are due to the
A
legnth if gap phases
3
Q
Cells can also exit the cell cycle for an extended time by entering
A
G0 phase
4
Q
What must be met before the cell cycle can transition to the next phase
A
Checkpoints
5
Q
must bind cyclins to become
activated and phosphorylate their
target proteins
A
Cyclin-dependent kinases (CDKs)
6
Q
Cdk regulation is carried out by
A
phosphorylation
7
Q
Drives the cyclic assembly and activation of cyclin-Cdk complexes
A
Changes in the concentration of cyclin
8
Q
The cell-cycle control system depends on
A
cyclin accumulation and degradation
9
Q
Continual transcription leads to a gradual increase in the
A
concentration of each cyclin over the course of the cell cycle
10
Q
Abrupt degradation of cyclins returns the Cdks to an
A
inactive state
11
Q
Degradation of cyclins occurs via the
A
proteasome
12
Q
Cyclins are tagged with a chain of ubiquitin by an enzyme called
the
A
anaphase-promoting complex (APC/C)
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
14
Q
Cdk activity can also be blocked by the
A
binding of a Cdk inhibitor
15
Q
M-Cdk is inhibited by phosphorylation via the
A
kinase Wee1
16
Q
M-Cdk is activated by dephosphorylation by the
A
phosphatase Cdc25
17
Q
what is the target if phosphorylation
A
Cdk (not cyclin)
18
Q
Cdk activity thus requires both ___ on inhibitory sites
A
cyclin binding and dephosphorylation
19
Q
To progress into mitosis, M-Cdk must be
dephosphorylated by
A
Cdc25
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
21
Q
important to
prevent transmission of
mutations or inaccurate
chromosome separation
A
checkpoint
22
Q
Protein kinases respond to
DNA damage by
phosphorylating and
activating
A
p53
23
Q
activates transcription of a Cdk inhibitor
A
p53
24
Q
p53 is an important…
A
tumor suppressor gene, it many cancers
25
If the damage cannot be
repaired, p53 causes the
cell to
die
26
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
b
27
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.
b
a
28
the cell reorganizes and distributes its
components equally into two daughter cells in what phase
M phase
29
M phase includes
mitosis and cytokinesis
30
pulls the duplicated chromosomes apart
during mitosis
mitotic spindle
31
divides the cytoplasm into two halves
during cytokinesis
contractile ring
32
Mitosis occurs in __ stages
5
33
Before M phase when events must take place
The cell’s DNA must be fully replicated, The centrosome must be
duplicated
34
Replicated chromosomes are held together at the
centromere
35
Before entering mitosis, sister chromatids
condense
36
Sister chromatids are held
together by protein complexes
called
cohesins
37
are protein complexes that help carry out
chromosome condensation
condensins
38
Phosphorylation of condensins by M-Cdk triggers the
assembly of
condensin complexes onto the DNA
39
The duplicated centrosomes become
spindle poles
40
New microtubules grow out from the
spindle poles and form the
mitotic spindle
41
originate from one spindle pole and interact with
microtubules from the other spindle pole
Interpolar microtubules
42
originate in random directions from either spindle pole and do
not interact with other microtubules
Astral microtubules
43
bind the kinetochores of duplicated chromosomes
Kinetochore microtubules
44
are protein complexes that form on the centromere of each
chromosome, attach to the plus end of microtubules
kinetochores
45
Before M phase begins, two critical events must be completed
1) The DNA of the chromosomes is replicated
2) The centrosome is duplicated
46
Interphase consists of what other phases
G1, S, G2
47
What phase: chromosomes condense, kinetochores assemble onto chromosomes
Prophase
48
What phase: The mitotic spindle assembles between the two centrosomes
Prophase
49
Phosphorylation of condensins by MCdk promotes...
prophase
50
are protein complexes that help carry out chromosome condensation
Condensins
51
Phosphorylation of condensins by MCdk triggers the assembly of
condensin complexes on DNA
52
Mitosis stage 2:
Prometaphase
53
What phase: The nuclear envelope breaks down and microtubules of mitotic spindle attach kinetochores on chromosomes
Prometaphase
54
Phosphorylation of nuclear lamins promotes
nuclear envelope breakdown during prometaphase
55
Mitosis stage 3:
metaphase
56
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
Metaphase
57
Mitosis stage 4
anaphase
58
What phase: The sister chromatids separate and are pulled toward the
spindle pole to which they are attached
anaphase
59
What phase: The kinetochore microtubules shorten, and the spindle poles
also move apart
anaphase
60
During anaphase, degradation of cohesin allows...
chromosome segregration
61
Sister chromatids are held
together by protein complexes
called
cohesins
62
The cohesin linkage during anaphase is destroyed by a protein called
separase
63
Before anaphase, separase is held in an active state by
securin
64
At the beginning of anaphase, securin is targeted for degradation by
APC/C
65
Anaphase A or B
spindle poles are pushed and pulled apart
kinetochore microtubules shorten, moving chromosomes
toward spindle poles
B
A
66
Mitosis stage 5:
Telophase
67
What phase: The two sets of chromosomes arrive at the spindle poles, a new nuclear envelope reassembles around each set of
chromosomes
Telophase
68
Dephosphorylation of nuclear lamins allows
reassembly of the nuclear envelope during telophase
69
What divides the cell into 2
cytokinesis
70
The cytoplasm is divided in two by a ____
contractile ring of actin
and myosin
71
contractile ring of actin and myosin
contractile ring
72
Sliding of actin filaments against the myosin filaments generates a
force that creates a
a cleavage furrow and divides the cell in two
73
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
C
B
F
E
A
D
74
Kinetochores assemble on what region of chromosome
centromere
75
If cells are no longer needed, they can remove themselves via
apoptosis
76
Cell death plays a critical role during
animal/body development
77
In adults, the rate of cell death = the rate of __
cell proliferation
78
Apoptosis allows cells to die __
individually
79
engulf the apoptotic cell before its contents can leak out
Phagocytic cells
80
cells that die as a result of
acute injury undergo
necrosis
81
The cell swells and bursts is
necrosis
82
This triggers a potentially damaging
inflammatory response
necrosis
83
proteases that are responsible for apoptosis
Caspases
84
Caspases are made as inactive precursors called
procaspases
85
cleave and activate executioner caspases
Initiator caspases
86
Procaspases are activated in response to signals that
induce apoptosis
87
Active executioner caspases __ many proteins in the cell
degrade
88
control release of the protein cytochrome c from
mitochondria into the cytosol
Bcl2 family proteins
89
Caspase activity is tightly regulated by the
Bcl2 family of proteins
90
Two Bcl2 family members, ___ and ___ , promote cytochrome c release. Other family members inhibit release.
Bax and Bak
91
Once released into the cytosol, cytochrome c activates initiator
procaspases by promoting the assembly of a large protein complex called
the
apoptosome
92
In a multicellular organism, the fate of individual
cells is controlled by
signals from other cells
93
Three major categories of signal proteins
Survival factors promote cell survival
* Mitogens stimulate cell division
* Growth factors stimulate cell growth
94
Survival factors usually act through
cell surface receptors
95
When survival factors cell surface receptors are activated, they turn on intracellular signaling pathways that...
inhibit apoptosis
96
Most survival factors activate signaling pathways that regulate members
of the
Bcl2 family
97
stimulate cell division by promoting
entry into S phase
Mitogens
98
Most mitogens are secreted proteins that bind
cell-surface
receptors
99
Mitogens intracellular signaling pathways act mainly by
promoting the
transition from G1 phase into S phase
100
some factors can act as both __ and __
by promoting both cell growth and division
mitogens and growth factors
101
binds transcription regulators and prevents them
from turning on genes required for cell division
Retinoblastoma protein (Rb)
102
Mitogens trigger the activation of
G1-Cdk and G1/S-Cdk
103
Role of G1-Cdk and G1/S-Cdk
phosphorylate Rb protein
104
phosphorylate Rb protein alters the ___ of Rb and it releases ___ so that it can activate ___ required for ___ into __ phase
conformation, bound transcription regulators so they can activate genes required for entry into S phase
105
promote the
accumulation of proteins and other
macromolecules
Growth factors intracellular signaling pathway
106
promote protein synthesis and inhibit protein degradation
Growth factors
107
Binding of a growth factor to a
receptor tyrosine kinase (RTK) initiates an
intracellular signaling pathway that leads to
activation of
Akt and Tor
108
Example of what stimulates
protein synthesis and inhibits protein
degradation
Akt and Tor
