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Chapter 18: Cell Cycle Flashcards

1
Q

What is the basic function of the cell cycle?

A

Cell duplicating their DNA and dividing in 2

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2
Q

What are the three steps of the cell cycle?

A
  1. Cell growth and development
  2. Chromosome segregation
  3. Cell division
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3
Q

What are the 4 phases of the cell cycle?

A
  1. G1 phase
  2. M Phase
  3. S Phase
  4. G2 Phase
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4
Q

What are the phases in the interphase of the cell cycle?

A

G1, S, G2

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5
Q

What happens in the M Phase?

A

mitosis and cytokinesis

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6
Q

What happens during S phase?

A

the cell replicates its DNA

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7
Q

What happens during the G1 and G2 phase?

A

Cell grows in size

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8
Q

What is the cell cycle control system?

A

internal and external conditions are monitored in G1
, G2 and M phases to ensure that the cell is prepared to pass through key steps of the cell cycle (Checkpoints) and that these steps occur in the appropriate sequence

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9
Q

Where are the three checkpoints?

A

Between G1 and S
Between G2 and M
During M Phase

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10
Q

What happens if the cell did not have a control system?

A

Cancer development can result from defects

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11
Q

What happens at the checkpoint between the G1 and S phase?

A

the control system confirms that the environment is favorable for proliferation before committing to DNA replication.

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12
Q

What happens at the checkpoint between the G2 and M phase?

A

the control system confirms that the DNA is undamaged
and fully replicated, ensuring that the cell does not enter mitosis unless its DNA is intact.

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13
Q

What happens at the checkpoint during mitosis?

A

the control system confirms that the duplicated chromosomes are properly attached to the mitotic spindle before the spindle pulls the chromosome apart

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14
Q

What did researcher find out after injecting cytoplasm into the M phase?

A

Oocyte is driven into M phase

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15
Q

What did they conclude about the cytoplasm?

A

Cytoplasm correlates with a mechanism (MPF) that is a component involved in the cell cycle control

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16
Q

What is MPF

A

maturation promoting factor: molecule of mechanism responsible for promoting the M phase

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17
Q

What are the two components that induce mitosis?

A

M-cyclin and Cdk

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18
Q

What does the progression of the cell cycle depends on?

A

phosphorylation occur by cyclin dependent protein kinases (Cdks)

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19
Q

What is cdk?

A

protein kinase that induce phosphorylation to progress the cell cycle

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20
Q

When are cdk only active?

A

When they bind to cyclin forming cyclin-cdk complex

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21
Q

What controls the timing of cdk activation

A

concentration of the partner cyclins,

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22
Q

True or False: Progression through each
phase of the cell cycle requires a specific cyclin
and Cdk partner

A

True

These cyclin-Cdk complexes activate different sets of target proteins

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23
Q

What causes increase in cyclin proteins at different stages of cell cycle?

A

Continued transcription of cyclin genes and synthesis of cyclin proteins

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24
Q

What causes a decrease in Cyclin Concentrations

A

Targeted destruction by the anaphase-promoting complex APC/C enzyme which tags M and S cyclins with ubiquitin, marking them for degradation in the proteosome

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25
How are cyclin concentration regulated?
Transcription and by Proteolysis
26
What regulates cyclin-cdk complex activity?
Phosphorylation and Dephosphorylation
27
What activates cyclin-cdk activity?
dephosphorylated by a cdc 25 because cdk contain inhibitory phosphate
28
Why would the cell control system want to use Cdk inhibitor proteins.
block the assembly or activity of certain cyclin–Cdk complexes. inhibitors maintain Cdks in an inactive state this gives more time for cell to grow
29
How can activated M-Cdk indirectly activates more M-Cdk
Positive feedback
30
How would positive feedback from m-cdk be significant to the progression of the cell cycle?
Allows massive amplification of the signal to initiate M phase processes
31
How can cdk contribute to negative feedback?
It can contribute to its own delayed inactivation by activating its ubiquitylating protein complex
32
How would the cell cycle control system respond if DNA replication is not complete or DNA is damaged?
It would inhibit the phosphatase (cdc 25) from removing the phosphate from the m-cdk-cyclin complex, preventing the cell from entering mitosis
33
How would the cell cycle control system respond if the chromosomes were not properly attached to spindle?
Inhibition of APC/C activation, which prevents the degradation of M cyclin and delay the cell from exiting the M phase
34
How would the cell cycle control system respond if cell environment were not favorable?
Cdk inhibitor block entry to S phase
35
What does the G1 phase consist of?
1. increased metabolic activity to increase cell size and duplicate all cells compartments 2. ensuring the DNA is “ready” for duplication (no breaks, etc.)
36
What must happen to the cdk in order for the cell to proceed from G1 and S phase?
Cdk must be activated by binding to cyclin
37
What are mitogens?
Extracellular signals produced by other cells that promote the production of the cyclins that stimulate cell division
38
What does mitogen do?
switching on cell signaling pathways that stimulate the synthesis of G1 cyclins, G1/S cyclins, and other proteins involved in DNA synthesis and chromosome duplication
39
What does Retinoblastoma protein (Rb) do?
prevents cells from turning on genes required for cell proliferation by binding transcription regulators
40
How does mitogen inhibit Rb?
triggering the activation of G1/S-Cdks, and S-Cdks which phosphorylate Rb, inactivating it
41
Why would a cell be arrested in its G1 phase?
DNA damage
42
What cause the cell to be arrested in its G1 phase?
DNA damage cause an increase in p53. P53 activates p21 which binds to G1/S-Cdk and S-Cdk, preventing them from driving the cell into S phase
43
What is p53?
transcription regulator that activates the gene encoding a Cdk inhibitor protein called p21
44
What happens if DNA damage is too severe to be repaired?
p53 can induce the cell to kill itself through apoptosis
45
What is G0?
Arrested state of cell
46
What is the origin of replication?
DNA sequence where replication will begin
47
What is the origin recognition complex?
region perched on the replication origin that recruits Cdc6
48
Why does ORC need to recruit cdc6
They recruit helicase to open to open DNA double helix
49
What needs to be phosphorylated before replication?
Cdc6, ORC and DNA helicase
50
What phosphoorylated Cdc6, ORC and DNA helicase for DNA replication?
S-cyclin/Cdk
51
What happens when Cdc6 is phosphorylated by S-cyclin/cdk?
Its degradation is promoted preventing re-initiation
52
What does mitosis and cytokinesis do?
segregating all cell components and accurately dividing DNA and organelles between the two daughter cells
53
What drives almost all stages of mitosis?
M-cdk complex
54
What activates m-cdk?
Cdc25 remove inhibition from m-cdk complex leading to positive feedback
55
What inactivate m-cdk
Activated M-Cdk turns on APC/C, leading to destruction of M cyclin, resulting in inactivation
56
What are the protein that help ensure separation of 2 daughter cells is successful?
Cohesin and Condensin
57
What does cohesin do?
holds two sister chromatids together during DNA replication to allow correct chromosome separation during mitosis
58
What does condensin do?
help promote chromosome condensation for easy segregation upon division
59
What does condensin?
help promote chromosome condensation for easy segregation upon division
60
What are mitotic spindle?
microtubules and associated motor proteins, responsible for separating the duplicated chromosomes, allocating one copy per daughter cell
61
What are contractile ring?
actin and myosin filaments arranged in a ring around the equator of the cell.
62
What does contractile ring do?
Contract the ring and pulls the membrane inward dividing the cell into two
63
What are the 5 phases of mitosis?
1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase
64
What happens in interphase?
Cell grow in size (G1) and DNA is replicated (S)
65
What happen in prophase?
The chromosome condensed
66
What are kinetochores?
protein complex assembled at centromeres, serve as docking for mitotic spindle
67
What are centrosome?
microtubules organizing center centromere referes to the center of chromatid
68
How does kinetochore play a role in mitosis?
serve as a docking site to connect chromosomes to microtubules in order to distribute the replicated genome from a mother cell to its daughters.
69
What happen in prometaphase?
nuclear envelope breakdown and chromosome can attach to mitotic spindle via kinetochore
70
What happen in metaphase?
chromosome are alligned in the equator by the microtubules that are attached to the kinetochore of each chromatid
71
How does centrosome form poles of mitotic spindle?
centrosome separate into two asters that move to the opposite sides of the nucleus to form poles of the mitotic spindle
72
What happens during anaphase?
1. sister chromatids are pulled apart. 2.kinetochore microtubules get shorter and the spindle poles also move apart 3. Cohesin linkage between the chromatids is destroyed at the beginning of anaphase 4. Nuclear envelope reassemble
73
What happens during cytokinesis?
Cytoplasm is divided in two by a contractile ring of actin and myosin filament, pinching the cell into two daughter cells
74
What is apoptosis?
process of programmed cell death
75
What is necrosis?
form of traumatic cell death that results from acute cellular injury.
76
Why is apoptosis advantage?
plays a key role during/for: - Development - Balance with cell division to maintain cell number - Removal of cells that compete for limited resources
77
What is apoptosis mediated by?
caspases
78
How does apoptosis help regulate cell number?
Cell death usually balances cell division 1.Some body parts are sculpted by apoptosis
79
What are the 2 apoptosis pathway?
1. Mitochondrial Damage (intracellular) 2. Death inducing signal from other cell (extracellular)
80
How is apoptosis pathway surpressed?
Bcl2
81
What does Bcl2 do?
Prevent Bax and Bak activation – inhibits apoptosis
82
What does Bax and Bak do?
release cytochrome C from mitochondria to activate apoptosis
83
What does cytochrome C (in the mitochondria) do?
activates initiator procaspases promotes formation of the apoptosome
83
What does cytochrome C (in the mitochondria) do?
activates initiator procaspases promotes formation of the apoptosome
84
What happens if there's a mutation in myostatin?
inhibits myoblast growth and proliferation results in massive increase in skeletal muscle mass – both cell number and size

Biology (20 decks)

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